Merge branch 'kvm-fixes-for-5.18-rc5' into HEAD

[sfrench/cifs-2.6.git] / virt / kvm / kvm_main.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kernel-based Virtual Machine driver for Linux
 *
 * This module enables machines with Intel VT-x extensions to run virtual
 * machines without emulation or binary translation.
 *
 * Copyright (C) 2006 Qumranet, Inc.
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * Authors:
 *   Avi Kivity   <avi@qumranet.com>
 *   Yaniv Kamay  <yaniv@qumranet.com>
 */

#include <kvm/iodev.h>

#include <linux/kvm_host.h>
#include <linux/kvm.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/percpu.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/vmalloc.h>
#include <linux/reboot.h>
#include <linux/debugfs.h>
#include <linux/highmem.h>
#include <linux/file.h>
#include <linux/syscore_ops.h>
#include <linux/cpu.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/sched/stat.h>
#include <linux/cpumask.h>
#include <linux/smp.h>
#include <linux/anon_inodes.h>
#include <linux/profile.h>
#include <linux/kvm_para.h>
#include <linux/pagemap.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/compat.h>
#include <linux/srcu.h>
#include <linux/hugetlb.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/bsearch.h>
#include <linux/io.h>
#include <linux/lockdep.h>
#include <linux/kthread.h>
#include <linux/suspend.h>

#include <asm/processor.h>
#include <asm/ioctl.h>
#include <linux/uaccess.h>

#include "coalesced_mmio.h"
#include "async_pf.h"
#include "kvm_mm.h"
#include "vfio.h"

#define CREATE_TRACE_POINTS
#include <trace/events/kvm.h>

#include <linux/kvm_dirty_ring.h>

/* Worst case buffer size needed for holding an integer. */
#define ITOA_MAX_LEN 12

MODULE_AUTHOR("Qumranet");
MODULE_LICENSE("GPL");

/* Architectures should define their poll value according to the halt latency */
unsigned int halt_poll_ns = KVM_HALT_POLL_NS_DEFAULT;
module_param(halt_poll_ns, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns);

/* Default doubles per-vcpu halt_poll_ns. */
unsigned int halt_poll_ns_grow = 2;
module_param(halt_poll_ns_grow, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_grow);

/* The start value to grow halt_poll_ns from */
unsigned int halt_poll_ns_grow_start = 10000; /* 10us */
module_param(halt_poll_ns_grow_start, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_grow_start);

/* Default resets per-vcpu halt_poll_ns . */
unsigned int halt_poll_ns_shrink;
module_param(halt_poll_ns_shrink, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_shrink);

/*
 * Ordering of locks:
 *
 *      kvm->lock --> kvm->slots_lock --> kvm->irq_lock
 */

DEFINE_MUTEX(kvm_lock);
static DEFINE_RAW_SPINLOCK(kvm_count_lock);
LIST_HEAD(vm_list);

static cpumask_var_t cpus_hardware_enabled;
static int kvm_usage_count;
static atomic_t hardware_enable_failed;

static struct kmem_cache *kvm_vcpu_cache;

static __read_mostly struct preempt_ops kvm_preempt_ops;
static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu);

struct dentry *kvm_debugfs_dir;
EXPORT_SYMBOL_GPL(kvm_debugfs_dir);

static const struct file_operations stat_fops_per_vm;

static struct file_operations kvm_chardev_ops;

static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
                           unsigned long arg);
#ifdef CONFIG_KVM_COMPAT
static long kvm_vcpu_compat_ioctl(struct file *file, unsigned int ioctl,
                                  unsigned long arg);
#define KVM_COMPAT(c)   .compat_ioctl   = (c)
#else
/*
 * For architectures that don't implement a compat infrastructure,
 * adopt a double line of defense:
 * - Prevent a compat task from opening /dev/kvm
 * - If the open has been done by a 64bit task, and the KVM fd
 *   passed to a compat task, let the ioctls fail.
 */
static long kvm_no_compat_ioctl(struct file *file, unsigned int ioctl,
                                unsigned long arg) { return -EINVAL; }

static int kvm_no_compat_open(struct inode *inode, struct file *file)
{
        return is_compat_task() ? -ENODEV : 0;
}
#define KVM_COMPAT(c)   .compat_ioctl   = kvm_no_compat_ioctl,  \
                        .open           = kvm_no_compat_open
#endif
static int hardware_enable_all(void);
static void hardware_disable_all(void);

static void kvm_io_bus_destroy(struct kvm_io_bus *bus);

__visible bool kvm_rebooting;
EXPORT_SYMBOL_GPL(kvm_rebooting);

#define KVM_EVENT_CREATE_VM 0
#define KVM_EVENT_DESTROY_VM 1
static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm);
static unsigned long long kvm_createvm_count;
static unsigned long long kvm_active_vms;

static DEFINE_PER_CPU(cpumask_var_t, cpu_kick_mask);

__weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
                                                   unsigned long start, unsigned long end)
{
}

__weak void kvm_arch_guest_memory_reclaimed(struct kvm *kvm)
{
}

bool kvm_is_zone_device_pfn(kvm_pfn_t pfn)
{
        /*
         * The metadata used by is_zone_device_page() to determine whether or
         * not a page is ZONE_DEVICE is guaranteed to be valid if and only if
         * the device has been pinned, e.g. by get_user_pages().  WARN if the
         * page_count() is zero to help detect bad usage of this helper.
         */
        if (!pfn_valid(pfn) || WARN_ON_ONCE(!page_count(pfn_to_page(pfn))))
                return false;

        return is_zone_device_page(pfn_to_page(pfn));
}

bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
{
        /*
         * ZONE_DEVICE pages currently set PG_reserved, but from a refcounting
         * perspective they are "normal" pages, albeit with slightly different
         * usage rules.
         */
        if (pfn_valid(pfn))
                return PageReserved(pfn_to_page(pfn)) &&
                       !is_zero_pfn(pfn) &&
                       !kvm_is_zone_device_pfn(pfn);

        return true;
}

/*
 * Switches to specified vcpu, until a matching vcpu_put()
 */
void vcpu_load(struct kvm_vcpu *vcpu)
{
        int cpu = get_cpu();

        __this_cpu_write(kvm_running_vcpu, vcpu);
        preempt_notifier_register(&vcpu->preempt_notifier);
        kvm_arch_vcpu_load(vcpu, cpu);
        put_cpu();
}
EXPORT_SYMBOL_GPL(vcpu_load);

void vcpu_put(struct kvm_vcpu *vcpu)
{
        preempt_disable();
        kvm_arch_vcpu_put(vcpu);
        preempt_notifier_unregister(&vcpu->preempt_notifier);
        __this_cpu_write(kvm_running_vcpu, NULL);
        preempt_enable();
}
EXPORT_SYMBOL_GPL(vcpu_put);

/* TODO: merge with kvm_arch_vcpu_should_kick */
static bool kvm_request_needs_ipi(struct kvm_vcpu *vcpu, unsigned req)
{
        int mode = kvm_vcpu_exiting_guest_mode(vcpu);

        /*
         * We need to wait for the VCPU to reenable interrupts and get out of
         * READING_SHADOW_PAGE_TABLES mode.
         */
        if (req & KVM_REQUEST_WAIT)
                return mode != OUTSIDE_GUEST_MODE;

        /*
         * Need to kick a running VCPU, but otherwise there is nothing to do.
         */
        return mode == IN_GUEST_MODE;
}

static void ack_flush(void *_completed)
{
}

static inline bool kvm_kick_many_cpus(struct cpumask *cpus, bool wait)
{
        if (cpumask_empty(cpus))
                return false;

        smp_call_function_many(cpus, ack_flush, NULL, wait);
        return true;
}

static void kvm_make_vcpu_request(struct kvm_vcpu *vcpu, unsigned int req,
                                  struct cpumask *tmp, int current_cpu)
{
        int cpu;

        if (likely(!(req & KVM_REQUEST_NO_ACTION)))
                __kvm_make_request(req, vcpu);

        if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
                return;

        /*
         * Note, the vCPU could get migrated to a different pCPU at any point
         * after kvm_request_needs_ipi(), which could result in sending an IPI
         * to the previous pCPU.  But, that's OK because the purpose of the IPI
         * is to ensure the vCPU returns to OUTSIDE_GUEST_MODE, which is
         * satisfied if the vCPU migrates. Entering READING_SHADOW_PAGE_TABLES
         * after this point is also OK, as the requirement is only that KVM wait
         * for vCPUs that were reading SPTEs _before_ any changes were
         * finalized. See kvm_vcpu_kick() for more details on handling requests.
         */
        if (kvm_request_needs_ipi(vcpu, req)) {
                cpu = READ_ONCE(vcpu->cpu);
                if (cpu != -1 && cpu != current_cpu)
                        __cpumask_set_cpu(cpu, tmp);
        }
}

bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
                                 unsigned long *vcpu_bitmap)
{
        struct kvm_vcpu *vcpu;
        struct cpumask *cpus;
        int i, me;
        bool called;

        me = get_cpu();

        cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask);
        cpumask_clear(cpus);

        for_each_set_bit(i, vcpu_bitmap, KVM_MAX_VCPUS) {
                vcpu = kvm_get_vcpu(kvm, i);
                if (!vcpu)
                        continue;
                kvm_make_vcpu_request(vcpu, req, cpus, me);
        }

        called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
        put_cpu();

        return called;
}

bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
                                      struct kvm_vcpu *except)
{
        struct kvm_vcpu *vcpu;
        struct cpumask *cpus;
        unsigned long i;
        bool called;
        int me;

        me = get_cpu();

        cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask);
        cpumask_clear(cpus);

        kvm_for_each_vcpu(i, vcpu, kvm) {
                if (vcpu == except)
                        continue;
                kvm_make_vcpu_request(vcpu, req, cpus, me);
        }

        called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
        put_cpu();

        return called;
}

bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
{
        return kvm_make_all_cpus_request_except(kvm, req, NULL);
}
EXPORT_SYMBOL_GPL(kvm_make_all_cpus_request);

#ifndef CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL
void kvm_flush_remote_tlbs(struct kvm *kvm)
{
        ++kvm->stat.generic.remote_tlb_flush_requests;

        /*
         * We want to publish modifications to the page tables before reading
         * mode. Pairs with a memory barrier in arch-specific code.
         * - x86: smp_mb__after_srcu_read_unlock in vcpu_enter_guest
         * and smp_mb in walk_shadow_page_lockless_begin/end.
         * - powerpc: smp_mb in kvmppc_prepare_to_enter.
         *
         * There is already an smp_mb__after_atomic() before
         * kvm_make_all_cpus_request() reads vcpu->mode. We reuse that
         * barrier here.
         */
        if (!kvm_arch_flush_remote_tlb(kvm)
            || kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
                ++kvm->stat.generic.remote_tlb_flush;
}
EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
#endif

static void kvm_flush_shadow_all(struct kvm *kvm)
{
        kvm_arch_flush_shadow_all(kvm);
        kvm_arch_guest_memory_reclaimed(kvm);
}

#ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
                                               gfp_t gfp_flags)
{
        gfp_flags |= mc->gfp_zero;

        if (mc->kmem_cache)
                return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
        else
                return (void *)__get_free_page(gfp_flags);
}

int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min)
{
        void *obj;

        if (mc->nobjs >= min)
                return 0;
        while (mc->nobjs < ARRAY_SIZE(mc->objects)) {
                obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT);
                if (!obj)
                        return mc->nobjs >= min ? 0 : -ENOMEM;
                mc->objects[mc->nobjs++] = obj;
        }
        return 0;
}

int kvm_mmu_memory_cache_nr_free_objects(struct kvm_mmu_memory_cache *mc)
{
        return mc->nobjs;
}

void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
{
        while (mc->nobjs) {
                if (mc->kmem_cache)
                        kmem_cache_free(mc->kmem_cache, mc->objects[--mc->nobjs]);
                else
                        free_page((unsigned long)mc->objects[--mc->nobjs]);
        }
}

void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
{
        void *p;

        if (WARN_ON(!mc->nobjs))
                p = mmu_memory_cache_alloc_obj(mc, GFP_ATOMIC | __GFP_ACCOUNT);
        else
                p = mc->objects[--mc->nobjs];
        BUG_ON(!p);
        return p;
}
#endif

static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
{
        mutex_init(&vcpu->mutex);
        vcpu->cpu = -1;
        vcpu->kvm = kvm;
        vcpu->vcpu_id = id;
        vcpu->pid = NULL;
#ifndef __KVM_HAVE_ARCH_WQP
        rcuwait_init(&vcpu->wait);
#endif
        kvm_async_pf_vcpu_init(vcpu);

        kvm_vcpu_set_in_spin_loop(vcpu, false);
        kvm_vcpu_set_dy_eligible(vcpu, false);
        vcpu->preempted = false;
        vcpu->ready = false;
        preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);
        vcpu->last_used_slot = NULL;
}

static void kvm_vcpu_destroy(struct kvm_vcpu *vcpu)
{
        kvm_arch_vcpu_destroy(vcpu);
        kvm_dirty_ring_free(&vcpu->dirty_ring);

        /*
         * No need for rcu_read_lock as VCPU_RUN is the only place that changes
         * the vcpu->pid pointer, and at destruction time all file descriptors
         * are already gone.
         */
        put_pid(rcu_dereference_protected(vcpu->pid, 1));

        free_page((unsigned long)vcpu->run);
        kmem_cache_free(kvm_vcpu_cache, vcpu);
}

void kvm_destroy_vcpus(struct kvm *kvm)
{
        unsigned long i;
        struct kvm_vcpu *vcpu;

        kvm_for_each_vcpu(i, vcpu, kvm) {
                kvm_vcpu_destroy(vcpu);
                xa_erase(&kvm->vcpu_array, i);
        }

        atomic_set(&kvm->online_vcpus, 0);
}
EXPORT_SYMBOL_GPL(kvm_destroy_vcpus);

#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
{
        return container_of(mn, struct kvm, mmu_notifier);
}

static void kvm_mmu_notifier_invalidate_range(struct mmu_notifier *mn,
                                              struct mm_struct *mm,
                                              unsigned long start, unsigned long end)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int idx;

        idx = srcu_read_lock(&kvm->srcu);
        kvm_arch_mmu_notifier_invalidate_range(kvm, start, end);
        srcu_read_unlock(&kvm->srcu, idx);
}

typedef bool (*hva_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range);

typedef void (*on_lock_fn_t)(struct kvm *kvm, unsigned long start,
                             unsigned long end);

typedef void (*on_unlock_fn_t)(struct kvm *kvm);

struct kvm_hva_range {
        unsigned long start;
        unsigned long end;
        pte_t pte;
        hva_handler_t handler;
        on_lock_fn_t on_lock;
        on_unlock_fn_t on_unlock;
        bool flush_on_ret;
        bool may_block;
};

/*
 * Use a dedicated stub instead of NULL to indicate that there is no callback
 * function/handler.  The compiler technically can't guarantee that a real
 * function will have a non-zero address, and so it will generate code to
 * check for !NULL, whereas comparing against a stub will be elided at compile
 * time (unless the compiler is getting long in the tooth, e.g. gcc 4.9).
 */
static void kvm_null_fn(void)
{

}
#define IS_KVM_NULL_FN(fn) ((fn) == (void *)kvm_null_fn)

/* Iterate over each memslot intersecting [start, last] (inclusive) range */
#define kvm_for_each_memslot_in_hva_range(node, slots, start, last)          \
        for (node = interval_tree_iter_first(&slots->hva_tree, start, last); \
             node;                                                           \
             node = interval_tree_iter_next(node, start, last))      \

static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
                                                  const struct kvm_hva_range *range)
{
        bool ret = false, locked = false;
        struct kvm_gfn_range gfn_range;
        struct kvm_memory_slot *slot;
        struct kvm_memslots *slots;
        int i, idx;

        if (WARN_ON_ONCE(range->end <= range->start))
                return 0;

        /* A null handler is allowed if and only if on_lock() is provided. */
        if (WARN_ON_ONCE(IS_KVM_NULL_FN(range->on_lock) &&
                         IS_KVM_NULL_FN(range->handler)))
                return 0;

        idx = srcu_read_lock(&kvm->srcu);

        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                struct interval_tree_node *node;

                slots = __kvm_memslots(kvm, i);
                kvm_for_each_memslot_in_hva_range(node, slots,
                                                  range->start, range->end - 1) {
                        unsigned long hva_start, hva_end;

                        slot = container_of(node, struct kvm_memory_slot, hva_node[slots->node_idx]);
                        hva_start = max(range->start, slot->userspace_addr);
                        hva_end = min(range->end, slot->userspace_addr +
                                                  (slot->npages << PAGE_SHIFT));

                        /*
                         * To optimize for the likely case where the address
                         * range is covered by zero or one memslots, don't
                         * bother making these conditional (to avoid writes on
                         * the second or later invocation of the handler).
                         */
                        gfn_range.pte = range->pte;
                        gfn_range.may_block = range->may_block;

                        /*
                         * {gfn(page) | page intersects with [hva_start, hva_end)} =
                         * {gfn_start, gfn_start+1, ..., gfn_end-1}.
                         */
                        gfn_range.start = hva_to_gfn_memslot(hva_start, slot);
                        gfn_range.end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, slot);
                        gfn_range.slot = slot;

                        if (!locked) {
                                locked = true;
                                KVM_MMU_LOCK(kvm);
                                if (!IS_KVM_NULL_FN(range->on_lock))
                                        range->on_lock(kvm, range->start, range->end);
                                if (IS_KVM_NULL_FN(range->handler))
                                        break;
                        }
                        ret |= range->handler(kvm, &gfn_range);
                }
        }

        if (range->flush_on_ret && ret)
                kvm_flush_remote_tlbs(kvm);

        if (locked) {
                KVM_MMU_UNLOCK(kvm);
                if (!IS_KVM_NULL_FN(range->on_unlock))
                        range->on_unlock(kvm);
        }

        srcu_read_unlock(&kvm->srcu, idx);

        /* The notifiers are averse to booleans. :-( */
        return (int)ret;
}

static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
                                                unsigned long start,
                                                unsigned long end,
                                                pte_t pte,
                                                hva_handler_t handler)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        const struct kvm_hva_range range = {
                .start          = start,
                .end            = end,
                .pte            = pte,
                .handler        = handler,
                .on_lock        = (void *)kvm_null_fn,
                .on_unlock      = (void *)kvm_null_fn,
                .flush_on_ret   = true,
                .may_block      = false,
        };

        return __kvm_handle_hva_range(kvm, &range);
}

static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn,
                                                         unsigned long start,
                                                         unsigned long end,
                                                         hva_handler_t handler)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        const struct kvm_hva_range range = {
                .start          = start,
                .end            = end,
                .pte            = __pte(0),
                .handler        = handler,
                .on_lock        = (void *)kvm_null_fn,
                .on_unlock      = (void *)kvm_null_fn,
                .flush_on_ret   = false,
                .may_block      = false,
        };

        return __kvm_handle_hva_range(kvm, &range);
}
static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
                                        struct mm_struct *mm,
                                        unsigned long address,
                                        pte_t pte)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);

        trace_kvm_set_spte_hva(address);

        /*
         * .change_pte() must be surrounded by .invalidate_range_{start,end}().
         * If mmu_notifier_count is zero, then no in-progress invalidations,
         * including this one, found a relevant memslot at start(); rechecking
         * memslots here is unnecessary.  Note, a false positive (count elevated
         * by a different invalidation) is sub-optimal but functionally ok.
         */
        WARN_ON_ONCE(!READ_ONCE(kvm->mn_active_invalidate_count));
        if (!READ_ONCE(kvm->mmu_notifier_count))
                return;

        kvm_handle_hva_range(mn, address, address + 1, pte, kvm_set_spte_gfn);
}

void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,
                                   unsigned long end)
{
        /*
         * The count increase must become visible at unlock time as no
         * spte can be established without taking the mmu_lock and
         * count is also read inside the mmu_lock critical section.
         */
        kvm->mmu_notifier_count++;
        if (likely(kvm->mmu_notifier_count == 1)) {
                kvm->mmu_notifier_range_start = start;
                kvm->mmu_notifier_range_end = end;
        } else {
                /*
                 * Fully tracking multiple concurrent ranges has diminishing
                 * returns. Keep things simple and just find the minimal range
                 * which includes the current and new ranges. As there won't be
                 * enough information to subtract a range after its invalidate
                 * completes, any ranges invalidated concurrently will
                 * accumulate and persist until all outstanding invalidates
                 * complete.
                 */
                kvm->mmu_notifier_range_start =
                        min(kvm->mmu_notifier_range_start, start);
                kvm->mmu_notifier_range_end =
                        max(kvm->mmu_notifier_range_end, end);
        }
}

static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
                                        const struct mmu_notifier_range *range)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        const struct kvm_hva_range hva_range = {
                .start          = range->start,
                .end            = range->end,
                .pte            = __pte(0),
                .handler        = kvm_unmap_gfn_range,
                .on_lock        = kvm_inc_notifier_count,
                .on_unlock      = kvm_arch_guest_memory_reclaimed,
                .flush_on_ret   = true,
                .may_block      = mmu_notifier_range_blockable(range),
        };

        trace_kvm_unmap_hva_range(range->start, range->end);

        /*
         * Prevent memslot modification between range_start() and range_end()
         * so that conditionally locking provides the same result in both
         * functions.  Without that guarantee, the mmu_notifier_count
         * adjustments will be imbalanced.
         *
         * Pairs with the decrement in range_end().
         */
        spin_lock(&kvm->mn_invalidate_lock);
        kvm->mn_active_invalidate_count++;
        spin_unlock(&kvm->mn_invalidate_lock);

        gfn_to_pfn_cache_invalidate_start(kvm, range->start, range->end,
                                          hva_range.may_block);

        __kvm_handle_hva_range(kvm, &hva_range);

        return 0;
}

void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,
                                   unsigned long end)
{
        /*
         * This sequence increase will notify the kvm page fault that
         * the page that is going to be mapped in the spte could have
         * been freed.
         */
        kvm->mmu_notifier_seq++;
        smp_wmb();
        /*
         * The above sequence increase must be visible before the
         * below count decrease, which is ensured by the smp_wmb above
         * in conjunction with the smp_rmb in mmu_notifier_retry().
         */
        kvm->mmu_notifier_count--;
}

static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
                                        const struct mmu_notifier_range *range)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        const struct kvm_hva_range hva_range = {
                .start          = range->start,
                .end            = range->end,
                .pte            = __pte(0),
                .handler        = (void *)kvm_null_fn,
                .on_lock        = kvm_dec_notifier_count,
                .on_unlock      = (void *)kvm_null_fn,
                .flush_on_ret   = false,
                .may_block      = mmu_notifier_range_blockable(range),
        };
        bool wake;

        __kvm_handle_hva_range(kvm, &hva_range);

        /* Pairs with the increment in range_start(). */
        spin_lock(&kvm->mn_invalidate_lock);
        wake = (--kvm->mn_active_invalidate_count == 0);
        spin_unlock(&kvm->mn_invalidate_lock);

        /*
         * There can only be one waiter, since the wait happens under
         * slots_lock.
         */
        if (wake)
                rcuwait_wake_up(&kvm->mn_memslots_update_rcuwait);

        BUG_ON(kvm->mmu_notifier_count < 0);
}

static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
                                              struct mm_struct *mm,
                                              unsigned long start,
                                              unsigned long end)
{
        trace_kvm_age_hva(start, end);

        return kvm_handle_hva_range(mn, start, end, __pte(0), kvm_age_gfn);
}

static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
                                        struct mm_struct *mm,
                                        unsigned long start,
                                        unsigned long end)
{
        trace_kvm_age_hva(start, end);

        /*
         * Even though we do not flush TLB, this will still adversely
         * affect performance on pre-Haswell Intel EPT, where there is
         * no EPT Access Bit to clear so that we have to tear down EPT
         * tables instead. If we find this unacceptable, we can always
         * add a parameter to kvm_age_hva so that it effectively doesn't
         * do anything on clear_young.
         *
         * Also note that currently we never issue secondary TLB flushes
         * from clear_young, leaving this job up to the regular system
         * cadence. If we find this inaccurate, we might come up with a
         * more sophisticated heuristic later.
         */
        return kvm_handle_hva_range_no_flush(mn, start, end, kvm_age_gfn);
}

static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
                                       struct mm_struct *mm,
                                       unsigned long address)
{
        trace_kvm_test_age_hva(address);

        return kvm_handle_hva_range_no_flush(mn, address, address + 1,
                                             kvm_test_age_gfn);
}

static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
                                     struct mm_struct *mm)
{
        struct kvm *kvm = mmu_notifier_to_kvm(mn);
        int idx;

        idx = srcu_read_lock(&kvm->srcu);
        kvm_flush_shadow_all(kvm);
        srcu_read_unlock(&kvm->srcu, idx);
}

static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
        .invalidate_range       = kvm_mmu_notifier_invalidate_range,
        .invalidate_range_start = kvm_mmu_notifier_invalidate_range_start,
        .invalidate_range_end   = kvm_mmu_notifier_invalidate_range_end,
        .clear_flush_young      = kvm_mmu_notifier_clear_flush_young,
        .clear_young            = kvm_mmu_notifier_clear_young,
        .test_young             = kvm_mmu_notifier_test_young,
        .change_pte             = kvm_mmu_notifier_change_pte,
        .release                = kvm_mmu_notifier_release,
};

static int kvm_init_mmu_notifier(struct kvm *kvm)
{
        kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
        return mmu_notifier_register(&kvm->mmu_notifier, current->mm);
}

#else  /* !(CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER) */

static int kvm_init_mmu_notifier(struct kvm *kvm)
{
        return 0;
}

#endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */

#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
static int kvm_pm_notifier_call(struct notifier_block *bl,
                                unsigned long state,
                                void *unused)
{
        struct kvm *kvm = container_of(bl, struct kvm, pm_notifier);

        return kvm_arch_pm_notifier(kvm, state);
}

static void kvm_init_pm_notifier(struct kvm *kvm)
{
        kvm->pm_notifier.notifier_call = kvm_pm_notifier_call;
        /* Suspend KVM before we suspend ftrace, RCU, etc. */
        kvm->pm_notifier.priority = INT_MAX;
        register_pm_notifier(&kvm->pm_notifier);
}

static void kvm_destroy_pm_notifier(struct kvm *kvm)
{
        unregister_pm_notifier(&kvm->pm_notifier);
}
#else /* !CONFIG_HAVE_KVM_PM_NOTIFIER */
static void kvm_init_pm_notifier(struct kvm *kvm)
{
}

static void kvm_destroy_pm_notifier(struct kvm *kvm)
{
}
#endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */

static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
{
        if (!memslot->dirty_bitmap)
                return;

        kvfree(memslot->dirty_bitmap);
        memslot->dirty_bitmap = NULL;
}

/* This does not remove the slot from struct kvm_memslots data structures */
static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
{
        kvm_destroy_dirty_bitmap(slot);

        kvm_arch_free_memslot(kvm, slot);

        kfree(slot);
}

static void kvm_free_memslots(struct kvm *kvm, struct kvm_memslots *slots)
{
        struct hlist_node *idnode;
        struct kvm_memory_slot *memslot;
        int bkt;

        /*
         * The same memslot objects live in both active and inactive sets,
         * arbitrarily free using index '1' so the second invocation of this
         * function isn't operating over a structure with dangling pointers
         * (even though this function isn't actually touching them).
         */
        if (!slots->node_idx)
                return;

        hash_for_each_safe(slots->id_hash, bkt, idnode, memslot, id_node[1])
                kvm_free_memslot(kvm, memslot);
}

static umode_t kvm_stats_debugfs_mode(const struct _kvm_stats_desc *pdesc)
{
        switch (pdesc->desc.flags & KVM_STATS_TYPE_MASK) {
        case KVM_STATS_TYPE_INSTANT:
                return 0444;
        case KVM_STATS_TYPE_CUMULATIVE:
        case KVM_STATS_TYPE_PEAK:
        default:
                return 0644;
        }
}


static void kvm_destroy_vm_debugfs(struct kvm *kvm)
{
        int i;
        int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc +
                                      kvm_vcpu_stats_header.num_desc;

        if (IS_ERR(kvm->debugfs_dentry))
                return;

        debugfs_remove_recursive(kvm->debugfs_dentry);

        if (kvm->debugfs_stat_data) {
                for (i = 0; i < kvm_debugfs_num_entries; i++)
                        kfree(kvm->debugfs_stat_data[i]);
                kfree(kvm->debugfs_stat_data);
        }
}

static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
{
        static DEFINE_MUTEX(kvm_debugfs_lock);
        struct dentry *dent;
        char dir_name[ITOA_MAX_LEN * 2];
        struct kvm_stat_data *stat_data;
        const struct _kvm_stats_desc *pdesc;
        int i, ret;
        int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc +
                                      kvm_vcpu_stats_header.num_desc;

        if (!debugfs_initialized())
                return 0;

        snprintf(dir_name, sizeof(dir_name), "%d-%d", task_pid_nr(current), fd);
        mutex_lock(&kvm_debugfs_lock);
        dent = debugfs_lookup(dir_name, kvm_debugfs_dir);
        if (dent) {
                pr_warn_ratelimited("KVM: debugfs: duplicate directory %s\n", dir_name);
                dput(dent);
                mutex_unlock(&kvm_debugfs_lock);
                return 0;
        }
        dent = debugfs_create_dir(dir_name, kvm_debugfs_dir);
        mutex_unlock(&kvm_debugfs_lock);
        if (IS_ERR(dent))
                return 0;

        kvm->debugfs_dentry = dent;
        kvm->debugfs_stat_data = kcalloc(kvm_debugfs_num_entries,
                                         sizeof(*kvm->debugfs_stat_data),
                                         GFP_KERNEL_ACCOUNT);
        if (!kvm->debugfs_stat_data)
                return -ENOMEM;

        for (i = 0; i < kvm_vm_stats_header.num_desc; ++i) {
                pdesc = &kvm_vm_stats_desc[i];
                stat_data = kzalloc(sizeof(*stat_data), GFP_KERNEL_ACCOUNT);
                if (!stat_data)
                        return -ENOMEM;

                stat_data->kvm = kvm;
                stat_data->desc = pdesc;
                stat_data->kind = KVM_STAT_VM;
                kvm->debugfs_stat_data[i] = stat_data;
                debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
                                    kvm->debugfs_dentry, stat_data,
                                    &stat_fops_per_vm);
        }

        for (i = 0; i < kvm_vcpu_stats_header.num_desc; ++i) {
                pdesc = &kvm_vcpu_stats_desc[i];
                stat_data = kzalloc(sizeof(*stat_data), GFP_KERNEL_ACCOUNT);
                if (!stat_data)
                        return -ENOMEM;

                stat_data->kvm = kvm;
                stat_data->desc = pdesc;
                stat_data->kind = KVM_STAT_VCPU;
                kvm->debugfs_stat_data[i + kvm_vm_stats_header.num_desc] = stat_data;
                debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
                                    kvm->debugfs_dentry, stat_data,
                                    &stat_fops_per_vm);
        }

        ret = kvm_arch_create_vm_debugfs(kvm);
        if (ret) {
                kvm_destroy_vm_debugfs(kvm);
                return i;
        }

        return 0;
}

/*
 * Called after the VM is otherwise initialized, but just before adding it to
 * the vm_list.
 */
int __weak kvm_arch_post_init_vm(struct kvm *kvm)
{
        return 0;
}

/*
 * Called just after removing the VM from the vm_list, but before doing any
 * other destruction.
 */
void __weak kvm_arch_pre_destroy_vm(struct kvm *kvm)
{
}

/*
 * Called after per-vm debugfs created.  When called kvm->debugfs_dentry should
 * be setup already, so we can create arch-specific debugfs entries under it.
 * Cleanup should be automatic done in kvm_destroy_vm_debugfs() recursively, so
 * a per-arch destroy interface is not needed.
 */
int __weak kvm_arch_create_vm_debugfs(struct kvm *kvm)
{
        return 0;
}

static struct kvm *kvm_create_vm(unsigned long type)
{
        struct kvm *kvm = kvm_arch_alloc_vm();
        struct kvm_memslots *slots;
        int r = -ENOMEM;
        int i, j;

        if (!kvm)
                return ERR_PTR(-ENOMEM);

        KVM_MMU_LOCK_INIT(kvm);
        mmgrab(current->mm);
        kvm->mm = current->mm;
        kvm_eventfd_init(kvm);
        mutex_init(&kvm->lock);
        mutex_init(&kvm->irq_lock);
        mutex_init(&kvm->slots_lock);
        mutex_init(&kvm->slots_arch_lock);
        spin_lock_init(&kvm->mn_invalidate_lock);
        rcuwait_init(&kvm->mn_memslots_update_rcuwait);
        xa_init(&kvm->vcpu_array);

        INIT_LIST_HEAD(&kvm->gpc_list);
        spin_lock_init(&kvm->gpc_lock);

        INIT_LIST_HEAD(&kvm->devices);

        BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX);

        /*
         * Force subsequent debugfs file creations to fail if the VM directory
         * is not created (by kvm_create_vm_debugfs()).
         */
        kvm->debugfs_dentry = ERR_PTR(-ENOENT);

        if (init_srcu_struct(&kvm->srcu))
                goto out_err_no_srcu;
        if (init_srcu_struct(&kvm->irq_srcu))
                goto out_err_no_irq_srcu;

        refcount_set(&kvm->users_count, 1);
        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                for (j = 0; j < 2; j++) {
                        slots = &kvm->__memslots[i][j];

                        atomic_long_set(&slots->last_used_slot, (unsigned long)NULL);
                        slots->hva_tree = RB_ROOT_CACHED;
                        slots->gfn_tree = RB_ROOT;
                        hash_init(slots->id_hash);
                        slots->node_idx = j;

                        /* Generations must be different for each address space. */
                        slots->generation = i;
                }

                rcu_assign_pointer(kvm->memslots[i], &kvm->__memslots[i][0]);
        }

        for (i = 0; i < KVM_NR_BUSES; i++) {
                rcu_assign_pointer(kvm->buses[i],
                        kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL_ACCOUNT));
                if (!kvm->buses[i])
                        goto out_err_no_arch_destroy_vm;
        }

        kvm->max_halt_poll_ns = halt_poll_ns;

        r = kvm_arch_init_vm(kvm, type);
        if (r)
                goto out_err_no_arch_destroy_vm;

        r = hardware_enable_all();
        if (r)
                goto out_err_no_disable;

#ifdef CONFIG_HAVE_KVM_IRQFD
        INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
#endif

        r = kvm_init_mmu_notifier(kvm);
        if (r)
                goto out_err_no_mmu_notifier;

        r = kvm_arch_post_init_vm(kvm);
        if (r)
                goto out_err;

        mutex_lock(&kvm_lock);
        list_add(&kvm->vm_list, &vm_list);
        mutex_unlock(&kvm_lock);

        preempt_notifier_inc();
        kvm_init_pm_notifier(kvm);

        /*
         * When the fd passed to this ioctl() is opened it pins the module,
         * but try_module_get() also prevents getting a reference if the module
         * is in MODULE_STATE_GOING (e.g. if someone ran "rmmod --wait").
         */
        if (!try_module_get(kvm_chardev_ops.owner)) {
                r = -ENODEV;
                goto out_err;
        }

        return kvm;

out_err:
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
        if (kvm->mmu_notifier.ops)
                mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
#endif
out_err_no_mmu_notifier:
        hardware_disable_all();
out_err_no_disable:
        kvm_arch_destroy_vm(kvm);
out_err_no_arch_destroy_vm:
        WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count));
        for (i = 0; i < KVM_NR_BUSES; i++)
                kfree(kvm_get_bus(kvm, i));
        cleanup_srcu_struct(&kvm->irq_srcu);
out_err_no_irq_srcu:
        cleanup_srcu_struct(&kvm->srcu);
out_err_no_srcu:
        kvm_arch_free_vm(kvm);
        mmdrop(current->mm);
        return ERR_PTR(r);
}

static void kvm_destroy_devices(struct kvm *kvm)
{
        struct kvm_device *dev, *tmp;

        /*
         * We do not need to take the kvm->lock here, because nobody else
         * has a reference to the struct kvm at this point and therefore
         * cannot access the devices list anyhow.
         */
        list_for_each_entry_safe(dev, tmp, &kvm->devices, vm_node) {
                list_del(&dev->vm_node);
                dev->ops->destroy(dev);
        }
}

static void kvm_destroy_vm(struct kvm *kvm)
{
        int i;
        struct mm_struct *mm = kvm->mm;

        kvm_destroy_pm_notifier(kvm);
        kvm_uevent_notify_change(KVM_EVENT_DESTROY_VM, kvm);
        kvm_destroy_vm_debugfs(kvm);
        kvm_arch_sync_events(kvm);
        mutex_lock(&kvm_lock);
        list_del(&kvm->vm_list);
        mutex_unlock(&kvm_lock);
        kvm_arch_pre_destroy_vm(kvm);

        kvm_free_irq_routing(kvm);
        for (i = 0; i < KVM_NR_BUSES; i++) {
                struct kvm_io_bus *bus = kvm_get_bus(kvm, i);

                if (bus)
                        kvm_io_bus_destroy(bus);
                kvm->buses[i] = NULL;
        }
        kvm_coalesced_mmio_free(kvm);
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
        mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
        /*
         * At this point, pending calls to invalidate_range_start()
         * have completed but no more MMU notifiers will run, so
         * mn_active_invalidate_count may remain unbalanced.
         * No threads can be waiting in install_new_memslots as the
         * last reference on KVM has been dropped, but freeing
         * memslots would deadlock without this manual intervention.
         */
        WARN_ON(rcuwait_active(&kvm->mn_memslots_update_rcuwait));
        kvm->mn_active_invalidate_count = 0;
#else
        kvm_flush_shadow_all(kvm);
#endif
        kvm_arch_destroy_vm(kvm);
        kvm_destroy_devices(kvm);
        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                kvm_free_memslots(kvm, &kvm->__memslots[i][0]);
                kvm_free_memslots(kvm, &kvm->__memslots[i][1]);
        }
        cleanup_srcu_struct(&kvm->irq_srcu);
        cleanup_srcu_struct(&kvm->srcu);
        kvm_arch_free_vm(kvm);
        preempt_notifier_dec();
        hardware_disable_all();
        mmdrop(mm);
        module_put(kvm_chardev_ops.owner);
}

void kvm_get_kvm(struct kvm *kvm)
{
        refcount_inc(&kvm->users_count);
}
EXPORT_SYMBOL_GPL(kvm_get_kvm);

/*
 * Make sure the vm is not during destruction, which is a safe version of
 * kvm_get_kvm().  Return true if kvm referenced successfully, false otherwise.
 */
bool kvm_get_kvm_safe(struct kvm *kvm)
{
        return refcount_inc_not_zero(&kvm->users_count);
}
EXPORT_SYMBOL_GPL(kvm_get_kvm_safe);

void kvm_put_kvm(struct kvm *kvm)
{
        if (refcount_dec_and_test(&kvm->users_count))
                kvm_destroy_vm(kvm);
}
EXPORT_SYMBOL_GPL(kvm_put_kvm);

/*
 * Used to put a reference that was taken on behalf of an object associated
 * with a user-visible file descriptor, e.g. a vcpu or device, if installation
 * of the new file descriptor fails and the reference cannot be transferred to
 * its final owner.  In such cases, the caller is still actively using @kvm and
 * will fail miserably if the refcount unexpectedly hits zero.
 */
void kvm_put_kvm_no_destroy(struct kvm *kvm)
{
        WARN_ON(refcount_dec_and_test(&kvm->users_count));
}
EXPORT_SYMBOL_GPL(kvm_put_kvm_no_destroy);

static int kvm_vm_release(struct inode *inode, struct file *filp)
{
        struct kvm *kvm = filp->private_data;

        kvm_irqfd_release(kvm);

        kvm_put_kvm(kvm);
        return 0;
}

/*
 * Allocation size is twice as large as the actual dirty bitmap size.
 * See kvm_vm_ioctl_get_dirty_log() why this is needed.
 */
static int kvm_alloc_dirty_bitmap(struct kvm_memory_slot *memslot)
{
        unsigned long dirty_bytes = kvm_dirty_bitmap_bytes(memslot);

        memslot->dirty_bitmap = __vcalloc(2, dirty_bytes, GFP_KERNEL_ACCOUNT);
        if (!memslot->dirty_bitmap)
                return -ENOMEM;

        return 0;
}

static struct kvm_memslots *kvm_get_inactive_memslots(struct kvm *kvm, int as_id)
{
        struct kvm_memslots *active = __kvm_memslots(kvm, as_id);
        int node_idx_inactive = active->node_idx ^ 1;

        return &kvm->__memslots[as_id][node_idx_inactive];
}

/*
 * Helper to get the address space ID when one of memslot pointers may be NULL.
 * This also serves as a sanity that at least one of the pointers is non-NULL,
 * and that their address space IDs don't diverge.
 */
static int kvm_memslots_get_as_id(struct kvm_memory_slot *a,
                                  struct kvm_memory_slot *b)
{
        if (WARN_ON_ONCE(!a && !b))
                return 0;

        if (!a)
                return b->as_id;
        if (!b)
                return a->as_id;

        WARN_ON_ONCE(a->as_id != b->as_id);
        return a->as_id;
}

static void kvm_insert_gfn_node(struct kvm_memslots *slots,
                                struct kvm_memory_slot *slot)
{
        struct rb_root *gfn_tree = &slots->gfn_tree;
        struct rb_node **node, *parent;
        int idx = slots->node_idx;

        parent = NULL;
        for (node = &gfn_tree->rb_node; *node; ) {
                struct kvm_memory_slot *tmp;

                tmp = container_of(*node, struct kvm_memory_slot, gfn_node[idx]);
                parent = *node;
                if (slot->base_gfn < tmp->base_gfn)
                        node = &(*node)->rb_left;
                else if (slot->base_gfn > tmp->base_gfn)
                        node = &(*node)->rb_right;
                else
                        BUG();
        }

        rb_link_node(&slot->gfn_node[idx], parent, node);
        rb_insert_color(&slot->gfn_node[idx], gfn_tree);
}

static void kvm_erase_gfn_node(struct kvm_memslots *slots,
                               struct kvm_memory_slot *slot)
{
        rb_erase(&slot->gfn_node[slots->node_idx], &slots->gfn_tree);
}

static void kvm_replace_gfn_node(struct kvm_memslots *slots,
                                 struct kvm_memory_slot *old,
                                 struct kvm_memory_slot *new)
{
        int idx = slots->node_idx;

        WARN_ON_ONCE(old->base_gfn != new->base_gfn);

        rb_replace_node(&old->gfn_node[idx], &new->gfn_node[idx],
                        &slots->gfn_tree);
}

/*
 * Replace @old with @new in the inactive memslots.
 *
 * With NULL @old this simply adds @new.
 * With NULL @new this simply removes @old.
 *
 * If @new is non-NULL its hva_node[slots_idx] range has to be set
 * appropriately.
 */
static void kvm_replace_memslot(struct kvm *kvm,
                                struct kvm_memory_slot *old,
                                struct kvm_memory_slot *new)
{
        int as_id = kvm_memslots_get_as_id(old, new);
        struct kvm_memslots *slots = kvm_get_inactive_memslots(kvm, as_id);
        int idx = slots->node_idx;

        if (old) {
                hash_del(&old->id_node[idx]);
                interval_tree_remove(&old->hva_node[idx], &slots->hva_tree);

                if ((long)old == atomic_long_read(&slots->last_used_slot))
                        atomic_long_set(&slots->last_used_slot, (long)new);

                if (!new) {
                        kvm_erase_gfn_node(slots, old);
                        return;
                }
        }

        /*
         * Initialize @new's hva range.  Do this even when replacing an @old
         * slot, kvm_copy_memslot() deliberately does not touch node data.
         */
        new->hva_node[idx].start = new->userspace_addr;
        new->hva_node[idx].last = new->userspace_addr +
                                  (new->npages << PAGE_SHIFT) - 1;

        /*
         * (Re)Add the new memslot.  There is no O(1) interval_tree_replace(),
         * hva_node needs to be swapped with remove+insert even though hva can't
         * change when replacing an existing slot.
         */
        hash_add(slots->id_hash, &new->id_node[idx], new->id);
        interval_tree_insert(&new->hva_node[idx], &slots->hva_tree);

        /*
         * If the memslot gfn is unchanged, rb_replace_node() can be used to
         * switch the node in the gfn tree instead of removing the old and
         * inserting the new as two separate operations. Replacement is a
         * single O(1) operation versus two O(log(n)) operations for
         * remove+insert.
         */
        if (old && old->base_gfn == new->base_gfn) {
                kvm_replace_gfn_node(slots, old, new);
        } else {
                if (old)
                        kvm_erase_gfn_node(slots, old);
                kvm_insert_gfn_node(slots, new);
        }
}

static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)
{
        u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;

#ifdef __KVM_HAVE_READONLY_MEM
        valid_flags |= KVM_MEM_READONLY;
#endif

        if (mem->flags & ~valid_flags)
                return -EINVAL;

        return 0;
}

static void kvm_swap_active_memslots(struct kvm *kvm, int as_id)
{
        struct kvm_memslots *slots = kvm_get_inactive_memslots(kvm, as_id);

        /* Grab the generation from the activate memslots. */
        u64 gen = __kvm_memslots(kvm, as_id)->generation;

        WARN_ON(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
        slots->generation = gen | KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;

        /*
         * Do not store the new memslots while there are invalidations in
         * progress, otherwise the locking in invalidate_range_start and
         * invalidate_range_end will be unbalanced.
         */
        spin_lock(&kvm->mn_invalidate_lock);
        prepare_to_rcuwait(&kvm->mn_memslots_update_rcuwait);
        while (kvm->mn_active_invalidate_count) {
                set_current_state(TASK_UNINTERRUPTIBLE);
                spin_unlock(&kvm->mn_invalidate_lock);
                schedule();
                spin_lock(&kvm->mn_invalidate_lock);
        }
        finish_rcuwait(&kvm->mn_memslots_update_rcuwait);
        rcu_assign_pointer(kvm->memslots[as_id], slots);
        spin_unlock(&kvm->mn_invalidate_lock);

        /*
         * Acquired in kvm_set_memslot. Must be released before synchronize
         * SRCU below in order to avoid deadlock with another thread
         * acquiring the slots_arch_lock in an srcu critical section.
         */
        mutex_unlock(&kvm->slots_arch_lock);

        synchronize_srcu_expedited(&kvm->srcu);

        /*
         * Increment the new memslot generation a second time, dropping the
         * update in-progress flag and incrementing the generation based on
         * the number of address spaces.  This provides a unique and easily
         * identifiable generation number while the memslots are in flux.
         */
        gen = slots->generation & ~KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;

        /*
         * Generations must be unique even across address spaces.  We do not need
         * a global counter for that, instead the generation space is evenly split
         * across address spaces.  For example, with two address spaces, address
         * space 0 will use generations 0, 2, 4, ... while address space 1 will
         * use generations 1, 3, 5, ...
         */
        gen += KVM_ADDRESS_SPACE_NUM;

        kvm_arch_memslots_updated(kvm, gen);

        slots->generation = gen;
}

static int kvm_prepare_memory_region(struct kvm *kvm,
                                     const struct kvm_memory_slot *old,
                                     struct kvm_memory_slot *new,
                                     enum kvm_mr_change change)
{
        int r;

        /*
         * If dirty logging is disabled, nullify the bitmap; the old bitmap
         * will be freed on "commit".  If logging is enabled in both old and
         * new, reuse the existing bitmap.  If logging is enabled only in the
         * new and KVM isn't using a ring buffer, allocate and initialize a
         * new bitmap.
         */
        if (change != KVM_MR_DELETE) {
                if (!(new->flags & KVM_MEM_LOG_DIRTY_PAGES))
                        new->dirty_bitmap = NULL;
                else if (old && old->dirty_bitmap)
                        new->dirty_bitmap = old->dirty_bitmap;
                else if (!kvm->dirty_ring_size) {
                        r = kvm_alloc_dirty_bitmap(new);
                        if (r)
                                return r;

                        if (kvm_dirty_log_manual_protect_and_init_set(kvm))
                                bitmap_set(new->dirty_bitmap, 0, new->npages);
                }
        }

        r = kvm_arch_prepare_memory_region(kvm, old, new, change);

        /* Free the bitmap on failure if it was allocated above. */
        if (r && new && new->dirty_bitmap && old && !old->dirty_bitmap)
                kvm_destroy_dirty_bitmap(new);

        return r;
}

static void kvm_commit_memory_region(struct kvm *kvm,
                                     struct kvm_memory_slot *old,
                                     const struct kvm_memory_slot *new,
                                     enum kvm_mr_change change)
{
        /*
         * Update the total number of memslot pages before calling the arch
         * hook so that architectures can consume the result directly.
         */
        if (change == KVM_MR_DELETE)
                kvm->nr_memslot_pages -= old->npages;
        else if (change == KVM_MR_CREATE)
                kvm->nr_memslot_pages += new->npages;

        kvm_arch_commit_memory_region(kvm, old, new, change);

        switch (change) {
        case KVM_MR_CREATE:
                /* Nothing more to do. */
                break;
        case KVM_MR_DELETE:
                /* Free the old memslot and all its metadata. */
                kvm_free_memslot(kvm, old);
                break;
        case KVM_MR_MOVE:
        case KVM_MR_FLAGS_ONLY:
                /*
                 * Free the dirty bitmap as needed; the below check encompasses
                 * both the flags and whether a ring buffer is being used)
                 */
                if (old->dirty_bitmap && !new->dirty_bitmap)
                        kvm_destroy_dirty_bitmap(old);

                /*
                 * The final quirk.  Free the detached, old slot, but only its
                 * memory, not any metadata.  Metadata, including arch specific
                 * data, may be reused by @new.
                 */
                kfree(old);
                break;
        default:
                BUG();
        }
}

/*
 * Activate @new, which must be installed in the inactive slots by the caller,
 * by swapping the active slots and then propagating @new to @old once @old is
 * unreachable and can be safely modified.
 *
 * With NULL @old this simply adds @new to @active (while swapping the sets).
 * With NULL @new this simply removes @old from @active and frees it
 * (while also swapping the sets).
 */
static void kvm_activate_memslot(struct kvm *kvm,
                                 struct kvm_memory_slot *old,
                                 struct kvm_memory_slot *new)
{
        int as_id = kvm_memslots_get_as_id(old, new);

        kvm_swap_active_memslots(kvm, as_id);

        /* Propagate the new memslot to the now inactive memslots. */
        kvm_replace_memslot(kvm, old, new);
}

static void kvm_copy_memslot(struct kvm_memory_slot *dest,
                             const struct kvm_memory_slot *src)
{
        dest->base_gfn = src->base_gfn;
        dest->npages = src->npages;
        dest->dirty_bitmap = src->dirty_bitmap;
        dest->arch = src->arch;
        dest->userspace_addr = src->userspace_addr;
        dest->flags = src->flags;
        dest->id = src->id;
        dest->as_id = src->as_id;
}

static void kvm_invalidate_memslot(struct kvm *kvm,
                                   struct kvm_memory_slot *old,
                                   struct kvm_memory_slot *invalid_slot)
{
        /*
         * Mark the current slot INVALID.  As with all memslot modifications,
         * this must be done on an unreachable slot to avoid modifying the
         * current slot in the active tree.
         */
        kvm_copy_memslot(invalid_slot, old);
        invalid_slot->flags |= KVM_MEMSLOT_INVALID;
        kvm_replace_memslot(kvm, old, invalid_slot);

        /*
         * Activate the slot that is now marked INVALID, but don't propagate
         * the slot to the now inactive slots. The slot is either going to be
         * deleted or recreated as a new slot.
         */
        kvm_swap_active_memslots(kvm, old->as_id);

        /*
         * From this point no new shadow pages pointing to a deleted, or moved,
         * memslot will be created.  Validation of sp->gfn happens in:
         *      - gfn_to_hva (kvm_read_guest, gfn_to_pfn)
         *      - kvm_is_visible_gfn (mmu_check_root)
         */
        kvm_arch_flush_shadow_memslot(kvm, old);
        kvm_arch_guest_memory_reclaimed(kvm);

        /* Was released by kvm_swap_active_memslots, reacquire. */
        mutex_lock(&kvm->slots_arch_lock);

        /*
         * Copy the arch-specific field of the newly-installed slot back to the
         * old slot as the arch data could have changed between releasing
         * slots_arch_lock in install_new_memslots() and re-acquiring the lock
         * above.  Writers are required to retrieve memslots *after* acquiring
         * slots_arch_lock, thus the active slot's data is guaranteed to be fresh.
         */
        old->arch = invalid_slot->arch;
}

static void kvm_create_memslot(struct kvm *kvm,
                               struct kvm_memory_slot *new)
{
        /* Add the new memslot to the inactive set and activate. */
        kvm_replace_memslot(kvm, NULL, new);
        kvm_activate_memslot(kvm, NULL, new);
}

static void kvm_delete_memslot(struct kvm *kvm,
                               struct kvm_memory_slot *old,
                               struct kvm_memory_slot *invalid_slot)
{
        /*
         * Remove the old memslot (in the inactive memslots) by passing NULL as
         * the "new" slot, and for the invalid version in the active slots.
         */
        kvm_replace_memslot(kvm, old, NULL);
        kvm_activate_memslot(kvm, invalid_slot, NULL);
}

static void kvm_move_memslot(struct kvm *kvm,
                             struct kvm_memory_slot *old,
                             struct kvm_memory_slot *new,
                             struct kvm_memory_slot *invalid_slot)
{
        /*
         * Replace the old memslot in the inactive slots, and then swap slots
         * and replace the current INVALID with the new as well.
         */
        kvm_replace_memslot(kvm, old, new);
        kvm_activate_memslot(kvm, invalid_slot, new);
}

static void kvm_update_flags_memslot(struct kvm *kvm,
                                     struct kvm_memory_slot *old,
                                     struct kvm_memory_slot *new)
{
        /*
         * Similar to the MOVE case, but the slot doesn't need to be zapped as
         * an intermediate step. Instead, the old memslot is simply replaced
         * with a new, updated copy in both memslot sets.
         */
        kvm_replace_memslot(kvm, old, new);
        kvm_activate_memslot(kvm, old, new);
}

static int kvm_set_memslot(struct kvm *kvm,
                           struct kvm_memory_slot *old,
                           struct kvm_memory_slot *new,
                           enum kvm_mr_change change)
{
        struct kvm_memory_slot *invalid_slot;
        int r;

        /*
         * Released in kvm_swap_active_memslots.
         *
         * Must be held from before the current memslots are copied until
         * after the new memslots are installed with rcu_assign_pointer,
         * then released before the synchronize srcu in kvm_swap_active_memslots.
         *
         * When modifying memslots outside of the slots_lock, must be held
         * before reading the pointer to the current memslots until after all
         * changes to those memslots are complete.
         *
         * These rules ensure that installing new memslots does not lose
         * changes made to the previous memslots.
         */
        mutex_lock(&kvm->slots_arch_lock);

        /*
         * Invalidate the old slot if it's being deleted or moved.  This is
         * done prior to actually deleting/moving the memslot to allow vCPUs to
         * continue running by ensuring there are no mappings or shadow pages
         * for the memslot when it is deleted/moved.  Without pre-invalidation
         * (and without a lock), a window would exist between effecting the
         * delete/move and committing the changes in arch code where KVM or a
         * guest could access a non-existent memslot.
         *
         * Modifications are done on a temporary, unreachable slot.  The old
         * slot needs to be preserved in case a later step fails and the
         * invalidation needs to be reverted.
         */
        if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
                invalid_slot = kzalloc(sizeof(*invalid_slot), GFP_KERNEL_ACCOUNT);
                if (!invalid_slot) {
                        mutex_unlock(&kvm->slots_arch_lock);
                        return -ENOMEM;
                }
                kvm_invalidate_memslot(kvm, old, invalid_slot);
        }

        r = kvm_prepare_memory_region(kvm, old, new, change);
        if (r) {
                /*
                 * For DELETE/MOVE, revert the above INVALID change.  No
                 * modifications required since the original slot was preserved
                 * in the inactive slots.  Changing the active memslots also
                 * release slots_arch_lock.
                 */
                if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
                        kvm_activate_memslot(kvm, invalid_slot, old);
                        kfree(invalid_slot);
                } else {
                        mutex_unlock(&kvm->slots_arch_lock);
                }
                return r;
        }

        /*
         * For DELETE and MOVE, the working slot is now active as the INVALID
         * version of the old slot.  MOVE is particularly special as it reuses
         * the old slot and returns a copy of the old slot (in working_slot).
         * For CREATE, there is no old slot.  For DELETE and FLAGS_ONLY, the
         * old slot is detached but otherwise preserved.
         */
        if (change == KVM_MR_CREATE)
                kvm_create_memslot(kvm, new);
        else if (change == KVM_MR_DELETE)
                kvm_delete_memslot(kvm, old, invalid_slot);
        else if (change == KVM_MR_MOVE)
                kvm_move_memslot(kvm, old, new, invalid_slot);
        else if (change == KVM_MR_FLAGS_ONLY)
                kvm_update_flags_memslot(kvm, old, new);
        else
                BUG();

        /* Free the temporary INVALID slot used for DELETE and MOVE. */
        if (change == KVM_MR_DELETE || change == KVM_MR_MOVE)
                kfree(invalid_slot);

        /*
         * No need to refresh new->arch, changes after dropping slots_arch_lock
         * will directly hit the final, active memslot.  Architectures are
         * responsible for knowing that new->arch may be stale.
         */
        kvm_commit_memory_region(kvm, old, new, change);

        return 0;
}

static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
                                      gfn_t start, gfn_t end)
{
        struct kvm_memslot_iter iter;

        kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
                if (iter.slot->id != id)
                        return true;
        }

        return false;
}

/*
 * Allocate some memory and give it an address in the guest physical address
 * space.
 *
 * Discontiguous memory is allowed, mostly for framebuffers.
 *
 * Must be called holding kvm->slots_lock for write.
 */
int __kvm_set_memory_region(struct kvm *kvm,
                            const struct kvm_userspace_memory_region *mem)
{
        struct kvm_memory_slot *old, *new;
        struct kvm_memslots *slots;
        enum kvm_mr_change change;
        unsigned long npages;
        gfn_t base_gfn;
        int as_id, id;
        int r;

        r = check_memory_region_flags(mem);
        if (r)
                return r;

        as_id = mem->slot >> 16;
        id = (u16)mem->slot;

        /* General sanity checks */
        if ((mem->memory_size & (PAGE_SIZE - 1)) ||
            (mem->memory_size != (unsigned long)mem->memory_size))
                return -EINVAL;
        if (mem->guest_phys_addr & (PAGE_SIZE - 1))
                return -EINVAL;
        /* We can read the guest memory with __xxx_user() later on. */
        if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
            (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
             !access_ok((void __user *)(unsigned long)mem->userspace_addr,
                        mem->memory_size))
                return -EINVAL;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
                return -EINVAL;
        if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
                return -EINVAL;
        if ((mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
                return -EINVAL;

        slots = __kvm_memslots(kvm, as_id);

        /*
         * Note, the old memslot (and the pointer itself!) may be invalidated
         * and/or destroyed by kvm_set_memslot().
         */
        old = id_to_memslot(slots, id);

        if (!mem->memory_size) {
                if (!old || !old->npages)
                        return -EINVAL;

                if (WARN_ON_ONCE(kvm->nr_memslot_pages < old->npages))
                        return -EIO;

                return kvm_set_memslot(kvm, old, NULL, KVM_MR_DELETE);
        }

        base_gfn = (mem->guest_phys_addr >> PAGE_SHIFT);
        npages = (mem->memory_size >> PAGE_SHIFT);

        if (!old || !old->npages) {
                change = KVM_MR_CREATE;

                /*
                 * To simplify KVM internals, the total number of pages across
                 * all memslots must fit in an unsigned long.
                 */
                if ((kvm->nr_memslot_pages + npages) < kvm->nr_memslot_pages)
                        return -EINVAL;
        } else { /* Modify an existing slot. */
                if ((mem->userspace_addr != old->userspace_addr) ||
                    (npages != old->npages) ||
                    ((mem->flags ^ old->flags) & KVM_MEM_READONLY))
                        return -EINVAL;

                if (base_gfn != old->base_gfn)
                        change = KVM_MR_MOVE;
                else if (mem->flags != old->flags)
                        change = KVM_MR_FLAGS_ONLY;
                else /* Nothing to change. */
                        return 0;
        }

        if ((change == KVM_MR_CREATE || change == KVM_MR_MOVE) &&
            kvm_check_memslot_overlap(slots, id, base_gfn, base_gfn + npages))
                return -EEXIST;

        /* Allocate a slot that will persist in the memslot. */
        new = kzalloc(sizeof(*new), GFP_KERNEL_ACCOUNT);
        if (!new)
                return -ENOMEM;

        new->as_id = as_id;
        new->id = id;
        new->base_gfn = base_gfn;
        new->npages = npages;
        new->flags = mem->flags;
        new->userspace_addr = mem->userspace_addr;

        r = kvm_set_memslot(kvm, old, new, change);
        if (r)
                kfree(new);
        return r;
}
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);

int kvm_set_memory_region(struct kvm *kvm,
                          const struct kvm_userspace_memory_region *mem)
{
        int r;

        mutex_lock(&kvm->slots_lock);
        r = __kvm_set_memory_region(kvm, mem);
        mutex_unlock(&kvm->slots_lock);
        return r;
}
EXPORT_SYMBOL_GPL(kvm_set_memory_region);

static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
                                          struct kvm_userspace_memory_region *mem)
{
        if ((u16)mem->slot >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        return kvm_set_memory_region(kvm, mem);
}

#ifndef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
/**
 * kvm_get_dirty_log - get a snapshot of dirty pages
 * @kvm:        pointer to kvm instance
 * @log:        slot id and address to which we copy the log
 * @is_dirty:   set to '1' if any dirty pages were found
 * @memslot:    set to the associated memslot, always valid on success
 */
int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log,
                      int *is_dirty, struct kvm_memory_slot **memslot)
{
        struct kvm_memslots *slots;
        int i, as_id, id;
        unsigned long n;
        unsigned long any = 0;

        /* Dirty ring tracking is exclusive to dirty log tracking */
        if (kvm->dirty_ring_size)
                return -ENXIO;

        *memslot = NULL;
        *is_dirty = 0;

        as_id = log->slot >> 16;
        id = (u16)log->slot;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        slots = __kvm_memslots(kvm, as_id);
        *memslot = id_to_memslot(slots, id);
        if (!(*memslot) || !(*memslot)->dirty_bitmap)
                return -ENOENT;

        kvm_arch_sync_dirty_log(kvm, *memslot);

        n = kvm_dirty_bitmap_bytes(*memslot);

        for (i = 0; !any && i < n/sizeof(long); ++i)
                any = (*memslot)->dirty_bitmap[i];

        if (copy_to_user(log->dirty_bitmap, (*memslot)->dirty_bitmap, n))
                return -EFAULT;

        if (any)
                *is_dirty = 1;
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_get_dirty_log);

#else /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
/**
 * kvm_get_dirty_log_protect - get a snapshot of dirty pages
 *      and reenable dirty page tracking for the corresponding pages.
 * @kvm:        pointer to kvm instance
 * @log:        slot id and address to which we copy the log
 *
 * We need to keep it in mind that VCPU threads can write to the bitmap
 * concurrently. So, to avoid losing track of dirty pages we keep the
 * following order:
 *
 *    1. Take a snapshot of the bit and clear it if needed.
 *    2. Write protect the corresponding page.
 *    3. Copy the snapshot to the userspace.
 *    4. Upon return caller flushes TLB's if needed.
 *
 * Between 2 and 4, the guest may write to the page using the remaining TLB
 * entry.  This is not a problem because the page is reported dirty using
 * the snapshot taken before and step 4 ensures that writes done after
 * exiting to userspace will be logged for the next call.
 *
 */
static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int i, as_id, id;
        unsigned long n;
        unsigned long *dirty_bitmap;
        unsigned long *dirty_bitmap_buffer;
        bool flush;

        /* Dirty ring tracking is exclusive to dirty log tracking */
        if (kvm->dirty_ring_size)
                return -ENXIO;

        as_id = log->slot >> 16;
        id = (u16)log->slot;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        slots = __kvm_memslots(kvm, as_id);
        memslot = id_to_memslot(slots, id);
        if (!memslot || !memslot->dirty_bitmap)
                return -ENOENT;

        dirty_bitmap = memslot->dirty_bitmap;

        kvm_arch_sync_dirty_log(kvm, memslot);

        n = kvm_dirty_bitmap_bytes(memslot);
        flush = false;
        if (kvm->manual_dirty_log_protect) {
                /*
                 * Unlike kvm_get_dirty_log, we always return false in *flush,
                 * because no flush is needed until KVM_CLEAR_DIRTY_LOG.  There
                 * is some code duplication between this function and
                 * kvm_get_dirty_log, but hopefully all architecture
                 * transition to kvm_get_dirty_log_protect and kvm_get_dirty_log
                 * can be eliminated.
                 */
                dirty_bitmap_buffer = dirty_bitmap;
        } else {
                dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
                memset(dirty_bitmap_buffer, 0, n);

                KVM_MMU_LOCK(kvm);
                for (i = 0; i < n / sizeof(long); i++) {
                        unsigned long mask;
                        gfn_t offset;

                        if (!dirty_bitmap[i])
                                continue;

                        flush = true;
                        mask = xchg(&dirty_bitmap[i], 0);
                        dirty_bitmap_buffer[i] = mask;

                        offset = i * BITS_PER_LONG;
                        kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
                                                                offset, mask);
                }
                KVM_MMU_UNLOCK(kvm);
        }

        if (flush)
                kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);

        if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
                return -EFAULT;
        return 0;
}


/**
 * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
 * @kvm: kvm instance
 * @log: slot id and address to which we copy the log
 *
 * Steps 1-4 below provide general overview of dirty page logging. See
 * kvm_get_dirty_log_protect() function description for additional details.
 *
 * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
 * always flush the TLB (step 4) even if previous step failed  and the dirty
 * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
 * does not preclude user space subsequent dirty log read. Flushing TLB ensures
 * writes will be marked dirty for next log read.
 *
 *   1. Take a snapshot of the bit and clear it if needed.
 *   2. Write protect the corresponding page.
 *   3. Copy the snapshot to the userspace.
 *   4. Flush TLB's if needed.
 */
static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
                                      struct kvm_dirty_log *log)
{
        int r;

        mutex_lock(&kvm->slots_lock);

        r = kvm_get_dirty_log_protect(kvm, log);

        mutex_unlock(&kvm->slots_lock);
        return r;
}

/**
 * kvm_clear_dirty_log_protect - clear dirty bits in the bitmap
 *      and reenable dirty page tracking for the corresponding pages.
 * @kvm:        pointer to kvm instance
 * @log:        slot id and address from which to fetch the bitmap of dirty pages
 */
static int kvm_clear_dirty_log_protect(struct kvm *kvm,
                                       struct kvm_clear_dirty_log *log)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int as_id, id;
        gfn_t offset;
        unsigned long i, n;
        unsigned long *dirty_bitmap;
        unsigned long *dirty_bitmap_buffer;
        bool flush;

        /* Dirty ring tracking is exclusive to dirty log tracking */
        if (kvm->dirty_ring_size)
                return -ENXIO;

        as_id = log->slot >> 16;
        id = (u16)log->slot;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
                return -EINVAL;

        if (log->first_page & 63)
                return -EINVAL;

        slots = __kvm_memslots(kvm, as_id);
        memslot = id_to_memslot(slots, id);
        if (!memslot || !memslot->dirty_bitmap)
                return -ENOENT;

        dirty_bitmap = memslot->dirty_bitmap;

        n = ALIGN(log->num_pages, BITS_PER_LONG) / 8;

        if (log->first_page > memslot->npages ||
            log->num_pages > memslot->npages - log->first_page ||
            (log->num_pages < memslot->npages - log->first_page && (log->num_pages & 63)))
            return -EINVAL;

        kvm_arch_sync_dirty_log(kvm, memslot);

        flush = false;
        dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
        if (copy_from_user(dirty_bitmap_buffer, log->dirty_bitmap, n))
                return -EFAULT;

        KVM_MMU_LOCK(kvm);
        for (offset = log->first_page, i = offset / BITS_PER_LONG,
                 n = DIV_ROUND_UP(log->num_pages, BITS_PER_LONG); n--;
             i++, offset += BITS_PER_LONG) {
                unsigned long mask = *dirty_bitmap_buffer++;
                atomic_long_t *p = (atomic_long_t *) &dirty_bitmap[i];
                if (!mask)
                        continue;

                mask &= atomic_long_fetch_andnot(mask, p);

                /*
                 * mask contains the bits that really have been cleared.  This
                 * never includes any bits beyond the length of the memslot (if
                 * the length is not aligned to 64 pages), therefore it is not
                 * a problem if userspace sets them in log->dirty_bitmap.
                */
                if (mask) {
                        flush = true;
                        kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
                                                                offset, mask);
                }
        }
        KVM_MMU_UNLOCK(kvm);

        if (flush)
                kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);

        return 0;
}

static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
                                        struct kvm_clear_dirty_log *log)
{
        int r;

        mutex_lock(&kvm->slots_lock);

        r = kvm_clear_dirty_log_protect(kvm, log);

        mutex_unlock(&kvm->slots_lock);
        return r;
}
#endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */

struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
{
        return __gfn_to_memslot(kvm_memslots(kvm), gfn);
}
EXPORT_SYMBOL_GPL(gfn_to_memslot);

struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        struct kvm_memslots *slots = kvm_vcpu_memslots(vcpu);
        u64 gen = slots->generation;
        struct kvm_memory_slot *slot;

        /*
         * This also protects against using a memslot from a different address space,
         * since different address spaces have different generation numbers.
         */
        if (unlikely(gen != vcpu->last_used_slot_gen)) {
                vcpu->last_used_slot = NULL;
                vcpu->last_used_slot_gen = gen;
        }

        slot = try_get_memslot(vcpu->last_used_slot, gfn);
        if (slot)
                return slot;

        /*
         * Fall back to searching all memslots. We purposely use
         * search_memslots() instead of __gfn_to_memslot() to avoid
         * thrashing the VM-wide last_used_slot in kvm_memslots.
         */
        slot = search_memslots(slots, gfn, false);
        if (slot) {
                vcpu->last_used_slot = slot;
                return slot;
        }

        return NULL;
}

bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_memory_slot *memslot = gfn_to_memslot(kvm, gfn);

        return kvm_is_visible_memslot(memslot);
}
EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);

bool kvm_vcpu_is_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        struct kvm_memory_slot *memslot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return kvm_is_visible_memslot(memslot);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_is_visible_gfn);

unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        struct vm_area_struct *vma;
        unsigned long addr, size;

        size = PAGE_SIZE;

        addr = kvm_vcpu_gfn_to_hva_prot(vcpu, gfn, NULL);
        if (kvm_is_error_hva(addr))
                return PAGE_SIZE;

        mmap_read_lock(current->mm);
        vma = find_vma(current->mm, addr);
        if (!vma)
                goto out;

        size = vma_kernel_pagesize(vma);

out:
        mmap_read_unlock(current->mm);

        return size;
}

static bool memslot_is_readonly(const struct kvm_memory_slot *slot)
{
        return slot->flags & KVM_MEM_READONLY;
}

static unsigned long __gfn_to_hva_many(const struct kvm_memory_slot *slot, gfn_t gfn,
                                       gfn_t *nr_pages, bool write)
{
        if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                return KVM_HVA_ERR_BAD;

        if (memslot_is_readonly(slot) && write)
                return KVM_HVA_ERR_RO_BAD;

        if (nr_pages)
                *nr_pages = slot->npages - (gfn - slot->base_gfn);

        return __gfn_to_hva_memslot(slot, gfn);
}

static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
                                     gfn_t *nr_pages)
{
        return __gfn_to_hva_many(slot, gfn, nr_pages, true);
}

unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot,
                                        gfn_t gfn)
{
        return gfn_to_hva_many(slot, gfn, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_hva_memslot);

unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
        return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_hva);

unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        return gfn_to_hva_many(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn, NULL);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_hva);

/*
 * Return the hva of a @gfn and the R/W attribute if possible.
 *
 * @slot: the kvm_memory_slot which contains @gfn
 * @gfn: the gfn to be translated
 * @writable: used to return the read/write attribute of the @slot if the hva
 * is valid and @writable is not NULL
 */
unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot,
                                      gfn_t gfn, bool *writable)
{
        unsigned long hva = __gfn_to_hva_many(slot, gfn, NULL, false);

        if (!kvm_is_error_hva(hva) && writable)
                *writable = !memslot_is_readonly(slot);

        return hva;
}

unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool *writable)
{
        struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

        return gfn_to_hva_memslot_prot(slot, gfn, writable);
}

unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable)
{
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return gfn_to_hva_memslot_prot(slot, gfn, writable);
}

static inline int check_user_page_hwpoison(unsigned long addr)
{
        int rc, flags = FOLL_HWPOISON | FOLL_WRITE;

        rc = get_user_pages(addr, 1, flags, NULL, NULL);
        return rc == -EHWPOISON;
}

/*
 * The fast path to get the writable pfn which will be stored in @pfn,
 * true indicates success, otherwise false is returned.  It's also the
 * only part that runs if we can in atomic context.
 */
static bool hva_to_pfn_fast(unsigned long addr, bool write_fault,
                            bool *writable, kvm_pfn_t *pfn)
{
        struct page *page[1];

        /*
         * Fast pin a writable pfn only if it is a write fault request
         * or the caller allows to map a writable pfn for a read fault
         * request.
         */
        if (!(write_fault || writable))
                return false;

        if (get_user_page_fast_only(addr, FOLL_WRITE, page)) {
                *pfn = page_to_pfn(page[0]);

                if (writable)
                        *writable = true;
                return true;
        }

        return false;
}

/*
 * The slow path to get the pfn of the specified host virtual address,
 * 1 indicates success, -errno is returned if error is detected.
 */
static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
                           bool *writable, kvm_pfn_t *pfn)
{
        unsigned int flags = FOLL_HWPOISON;
        struct page *page;
        int npages = 0;

        might_sleep();

        if (writable)
                *writable = write_fault;

        if (write_fault)
                flags |= FOLL_WRITE;
        if (async)
                flags |= FOLL_NOWAIT;

        npages = get_user_pages_unlocked(addr, 1, &page, flags);
        if (npages != 1)
                return npages;

        /* map read fault as writable if possible */
        if (unlikely(!write_fault) && writable) {
                struct page *wpage;

                if (get_user_page_fast_only(addr, FOLL_WRITE, &wpage)) {
                        *writable = true;
                        put_page(page);
                        page = wpage;
                }
        }
        *pfn = page_to_pfn(page);
        return npages;
}

static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)
{
        if (unlikely(!(vma->vm_flags & VM_READ)))
                return false;

        if (write_fault && (unlikely(!(vma->vm_flags & VM_WRITE))))
                return false;

        return true;
}

static int kvm_try_get_pfn(kvm_pfn_t pfn)
{
        if (kvm_is_reserved_pfn(pfn))
                return 1;
        return get_page_unless_zero(pfn_to_page(pfn));
}

static int hva_to_pfn_remapped(struct vm_area_struct *vma,
                               unsigned long addr, bool write_fault,
                               bool *writable, kvm_pfn_t *p_pfn)
{
        kvm_pfn_t pfn;
        pte_t *ptep;
        spinlock_t *ptl;
        int r;

        r = follow_pte(vma->vm_mm, addr, &ptep, &ptl);
        if (r) {
                /*
                 * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
                 * not call the fault handler, so do it here.
                 */
                bool unlocked = false;
                r = fixup_user_fault(current->mm, addr,
                                     (write_fault ? FAULT_FLAG_WRITE : 0),
                                     &unlocked);
                if (unlocked)
                        return -EAGAIN;
                if (r)
                        return r;

                r = follow_pte(vma->vm_mm, addr, &ptep, &ptl);
                if (r)
                        return r;
        }

        if (write_fault && !pte_write(*ptep)) {
                pfn = KVM_PFN_ERR_RO_FAULT;
                goto out;
        }

        if (writable)
                *writable = pte_write(*ptep);
        pfn = pte_pfn(*ptep);

        /*
         * Get a reference here because callers of *hva_to_pfn* and
         * *gfn_to_pfn* ultimately call kvm_release_pfn_clean on the
         * returned pfn.  This is only needed if the VMA has VM_MIXEDMAP
         * set, but the kvm_try_get_pfn/kvm_release_pfn_clean pair will
         * simply do nothing for reserved pfns.
         *
         * Whoever called remap_pfn_range is also going to call e.g.
         * unmap_mapping_range before the underlying pages are freed,
         * causing a call to our MMU notifier.
         *
         * Certain IO or PFNMAP mappings can be backed with valid
         * struct pages, but be allocated without refcounting e.g.,
         * tail pages of non-compound higher order allocations, which
         * would then underflow the refcount when the caller does the
         * required put_page. Don't allow those pages here.
         */ 
        if (!kvm_try_get_pfn(pfn))
                r = -EFAULT;

out:
        pte_unmap_unlock(ptep, ptl);
        *p_pfn = pfn;

        return r;
}

/*
 * Pin guest page in memory and return its pfn.
 * @addr: host virtual address which maps memory to the guest
 * @atomic: whether this function can sleep
 * @async: whether this function need to wait IO complete if the
 *         host page is not in the memory
 * @write_fault: whether we should get a writable host page
 * @writable: whether it allows to map a writable host page for !@write_fault
 *
 * The function will map a writable host page for these two cases:
 * 1): @write_fault = true
 * 2): @write_fault = false && @writable, @writable will tell the caller
 *     whether the mapping is writable.
 */
kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
                     bool write_fault, bool *writable)
{
        struct vm_area_struct *vma;
        kvm_pfn_t pfn = 0;
        int npages, r;

        /* we can do it either atomically or asynchronously, not both */
        BUG_ON(atomic && async);

        if (hva_to_pfn_fast(addr, write_fault, writable, &pfn))
                return pfn;

        if (atomic)
                return KVM_PFN_ERR_FAULT;

        npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
        if (npages == 1)
                return pfn;

        mmap_read_lock(current->mm);
        if (npages == -EHWPOISON ||
              (!async && check_user_page_hwpoison(addr))) {
                pfn = KVM_PFN_ERR_HWPOISON;
                goto exit;
        }

retry:
        vma = vma_lookup(current->mm, addr);

        if (vma == NULL)
                pfn = KVM_PFN_ERR_FAULT;
        else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
                r = hva_to_pfn_remapped(vma, addr, write_fault, writable, &pfn);
                if (r == -EAGAIN)
                        goto retry;
                if (r < 0)
                        pfn = KVM_PFN_ERR_FAULT;
        } else {
                if (async && vma_is_valid(vma, write_fault))
                        *async = true;
                pfn = KVM_PFN_ERR_FAULT;
        }
exit:
        mmap_read_unlock(current->mm);
        return pfn;
}

kvm_pfn_t __gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn,
                               bool atomic, bool *async, bool write_fault,
                               bool *writable, hva_t *hva)
{
        unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);

        if (hva)
                *hva = addr;

        if (addr == KVM_HVA_ERR_RO_BAD) {
                if (writable)
                        *writable = false;
                return KVM_PFN_ERR_RO_FAULT;
        }

        if (kvm_is_error_hva(addr)) {
                if (writable)
                        *writable = false;
                return KVM_PFN_NOSLOT;
        }

        /* Do not map writable pfn in the readonly memslot. */
        if (writable && memslot_is_readonly(slot)) {
                *writable = false;
                writable = NULL;
        }

        return hva_to_pfn(addr, atomic, async, write_fault,
                          writable);
}
EXPORT_SYMBOL_GPL(__gfn_to_pfn_memslot);

kvm_pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault,
                      bool *writable)
{
        return __gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn, false, NULL,
                                    write_fault, writable, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);

kvm_pfn_t gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn)
{
        return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot);

kvm_pfn_t gfn_to_pfn_memslot_atomic(const struct kvm_memory_slot *slot, gfn_t gfn)
{
        return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);

kvm_pfn_t kvm_vcpu_gfn_to_pfn_atomic(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        return gfn_to_pfn_memslot_atomic(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_pfn_atomic);

kvm_pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
{
        return gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn);

kvm_pfn_t kvm_vcpu_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        return gfn_to_pfn_memslot(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_pfn);

int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
                            struct page **pages, int nr_pages)
{
        unsigned long addr;
        gfn_t entry = 0;

        addr = gfn_to_hva_many(slot, gfn, &entry);
        if (kvm_is_error_hva(addr))
                return -1;

        if (entry < nr_pages)
                return 0;

        return get_user_pages_fast_only(addr, nr_pages, FOLL_WRITE, pages);
}
EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);

static struct page *kvm_pfn_to_page(kvm_pfn_t pfn)
{
        if (is_error_noslot_pfn(pfn))
                return KVM_ERR_PTR_BAD_PAGE;

        if (kvm_is_reserved_pfn(pfn)) {
                WARN_ON(1);
                return KVM_ERR_PTR_BAD_PAGE;
        }

        return pfn_to_page(pfn);
}

struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
{
        kvm_pfn_t pfn;

        pfn = gfn_to_pfn(kvm, gfn);

        return kvm_pfn_to_page(pfn);
}
EXPORT_SYMBOL_GPL(gfn_to_page);

void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
{
        if (pfn == 0)
                return;

        if (dirty)
                kvm_release_pfn_dirty(pfn);
        else
                kvm_release_pfn_clean(pfn);
}

int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
{
        kvm_pfn_t pfn;
        void *hva = NULL;
        struct page *page = KVM_UNMAPPED_PAGE;

        if (!map)
                return -EINVAL;

        pfn = gfn_to_pfn(vcpu->kvm, gfn);
        if (is_error_noslot_pfn(pfn))
                return -EINVAL;

        if (pfn_valid(pfn)) {
                page = pfn_to_page(pfn);
                hva = kmap(page);
#ifdef CONFIG_HAS_IOMEM
        } else {
                hva = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB);
#endif
        }

        if (!hva)
                return -EFAULT;

        map->page = page;
        map->hva = hva;
        map->pfn = pfn;
        map->gfn = gfn;

        return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_map);

void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
{
        if (!map)
                return;

        if (!map->hva)
                return;

        if (map->page != KVM_UNMAPPED_PAGE)
                kunmap(map->page);
#ifdef CONFIG_HAS_IOMEM
        else
                memunmap(map->hva);
#endif

        if (dirty)
                kvm_vcpu_mark_page_dirty(vcpu, map->gfn);

        kvm_release_pfn(map->pfn, dirty);

        map->hva = NULL;
        map->page = NULL;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);

struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        kvm_pfn_t pfn;

        pfn = kvm_vcpu_gfn_to_pfn(vcpu, gfn);

        return kvm_pfn_to_page(pfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_page);

void kvm_release_page_clean(struct page *page)
{
        WARN_ON(is_error_page(page));

        kvm_release_pfn_clean(page_to_pfn(page));
}
EXPORT_SYMBOL_GPL(kvm_release_page_clean);

void kvm_release_pfn_clean(kvm_pfn_t pfn)
{
        if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn))
                put_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_clean);

void kvm_release_page_dirty(struct page *page)
{
        WARN_ON(is_error_page(page));

        kvm_release_pfn_dirty(page_to_pfn(page));
}
EXPORT_SYMBOL_GPL(kvm_release_page_dirty);

void kvm_release_pfn_dirty(kvm_pfn_t pfn)
{
        kvm_set_pfn_dirty(pfn);
        kvm_release_pfn_clean(pfn);
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty);

void kvm_set_pfn_dirty(kvm_pfn_t pfn)
{
        if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
                SetPageDirty(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);

void kvm_set_pfn_accessed(kvm_pfn_t pfn)
{
        if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
                mark_page_accessed(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);

static int next_segment(unsigned long len, int offset)
{
        if (len > PAGE_SIZE - offset)
                return PAGE_SIZE - offset;
        else
                return len;
}

static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
                                 void *data, int offset, int len)
{
        int r;
        unsigned long addr;

        addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
        if (kvm_is_error_hva(addr))
                return -EFAULT;
        r = __copy_from_user(data, (void __user *)addr + offset, len);
        if (r)
                return -EFAULT;
        return 0;
}

int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
                        int len)
{
        struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

        return __kvm_read_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_page);

int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data,
                             int offset, int len)
{
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return __kvm_read_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_page);

int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_read_guest_page(kvm, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_read_guest);

int kvm_vcpu_read_guest(struct kvm_vcpu *vcpu, gpa_t gpa, void *data, unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_vcpu_read_guest_page(vcpu, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest);

static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
                                   void *data, int offset, unsigned long len)
{
        int r;
        unsigned long addr;

        addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
        if (kvm_is_error_hva(addr))
                return -EFAULT;
        pagefault_disable();
        r = __copy_from_user_inatomic(data, (void __user *)addr + offset, len);
        pagefault_enable();
        if (r)
                return -EFAULT;
        return 0;
}

int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
                               void *data, unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        int offset = offset_in_page(gpa);

        return __kvm_read_guest_atomic(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic);

static int __kvm_write_guest_page(struct kvm *kvm,
                                  struct kvm_memory_slot *memslot, gfn_t gfn,
                                  const void *data, int offset, int len)
{
        int r;
        unsigned long addr;

        addr = gfn_to_hva_memslot(memslot, gfn);
        if (kvm_is_error_hva(addr))
                return -EFAULT;
        r = __copy_to_user((void __user *)addr + offset, data, len);
        if (r)
                return -EFAULT;
        mark_page_dirty_in_slot(kvm, memslot, gfn);
        return 0;
}

int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn,
                         const void *data, int offset, int len)
{
        struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

        return __kvm_write_guest_page(kvm, slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_write_guest_page);

int kvm_vcpu_write_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn,
                              const void *data, int offset, int len)
{
        struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

        return __kvm_write_guest_page(vcpu->kvm, slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest_page);

int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
                    unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_write_guest_page(kvm, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_write_guest);

int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
                         unsigned long len)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_vcpu_write_guest_page(vcpu, gfn, data, offset, seg);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                data += seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest);

static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots,
                                       struct gfn_to_hva_cache *ghc,
                                       gpa_t gpa, unsigned long len)
{
        int offset = offset_in_page(gpa);
        gfn_t start_gfn = gpa >> PAGE_SHIFT;
        gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT;
        gfn_t nr_pages_needed = end_gfn - start_gfn + 1;
        gfn_t nr_pages_avail;

        /* Update ghc->generation before performing any error checks. */
        ghc->generation = slots->generation;

        if (start_gfn > end_gfn) {
                ghc->hva = KVM_HVA_ERR_BAD;
                return -EINVAL;
        }

        /*
         * If the requested region crosses two memslots, we still
         * verify that the entire region is valid here.
         */
        for ( ; start_gfn <= end_gfn; start_gfn += nr_pages_avail) {
                ghc->memslot = __gfn_to_memslot(slots, start_gfn);
                ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn,
                                           &nr_pages_avail);
                if (kvm_is_error_hva(ghc->hva))
                        return -EFAULT;
        }

        /* Use the slow path for cross page reads and writes. */
        if (nr_pages_needed == 1)
                ghc->hva += offset;
        else
                ghc->memslot = NULL;

        ghc->gpa = gpa;
        ghc->len = len;
        return 0;
}

int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                              gpa_t gpa, unsigned long len)
{
        struct kvm_memslots *slots = kvm_memslots(kvm);
        return __kvm_gfn_to_hva_cache_init(slots, ghc, gpa, len);
}
EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);

int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                                  void *data, unsigned int offset,
                                  unsigned long len)
{
        struct kvm_memslots *slots = kvm_memslots(kvm);
        int r;
        gpa_t gpa = ghc->gpa + offset;

        if (WARN_ON_ONCE(len + offset > ghc->len))
                return -EINVAL;

        if (slots->generation != ghc->generation) {
                if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
                        return -EFAULT;
        }

        if (kvm_is_error_hva(ghc->hva))
                return -EFAULT;

        if (unlikely(!ghc->memslot))
                return kvm_write_guest(kvm, gpa, data, len);

        r = __copy_to_user((void __user *)ghc->hva + offset, data, len);
        if (r)
                return -EFAULT;
        mark_page_dirty_in_slot(kvm, ghc->memslot, gpa >> PAGE_SHIFT);

        return 0;
}
EXPORT_SYMBOL_GPL(kvm_write_guest_offset_cached);

int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                           void *data, unsigned long len)
{
        return kvm_write_guest_offset_cached(kvm, ghc, data, 0, len);
}
EXPORT_SYMBOL_GPL(kvm_write_guest_cached);

int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                                 void *data, unsigned int offset,
                                 unsigned long len)
{
        struct kvm_memslots *slots = kvm_memslots(kvm);
        int r;
        gpa_t gpa = ghc->gpa + offset;

        if (WARN_ON_ONCE(len + offset > ghc->len))
                return -EINVAL;

        if (slots->generation != ghc->generation) {
                if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
                        return -EFAULT;
        }

        if (kvm_is_error_hva(ghc->hva))
                return -EFAULT;

        if (unlikely(!ghc->memslot))
                return kvm_read_guest(kvm, gpa, data, len);

        r = __copy_from_user(data, (void __user *)ghc->hva + offset, len);
        if (r)
                return -EFAULT;

        return 0;
}
EXPORT_SYMBOL_GPL(kvm_read_guest_offset_cached);

int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
                          void *data, unsigned long len)
{
        return kvm_read_guest_offset_cached(kvm, ghc, data, 0, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_cached);

int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
{
        const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0)));
        gfn_t gfn = gpa >> PAGE_SHIFT;
        int seg;
        int offset = offset_in_page(gpa);
        int ret;

        while ((seg = next_segment(len, offset)) != 0) {
                ret = kvm_write_guest_page(kvm, gfn, zero_page, offset, len);
                if (ret < 0)
                        return ret;
                offset = 0;
                len -= seg;
                ++gfn;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(kvm_clear_guest);

void mark_page_dirty_in_slot(struct kvm *kvm,
                             const struct kvm_memory_slot *memslot,
                             gfn_t gfn)
{
        struct kvm_vcpu *vcpu = kvm_get_running_vcpu();

#ifdef CONFIG_HAVE_KVM_DIRTY_RING
        if (WARN_ON_ONCE(!vcpu) || WARN_ON_ONCE(vcpu->kvm != kvm))
                return;
#endif

        if (memslot && kvm_slot_dirty_track_enabled(memslot)) {
                unsigned long rel_gfn = gfn - memslot->base_gfn;
                u32 slot = (memslot->as_id << 16) | memslot->id;

                if (kvm->dirty_ring_size)
                        kvm_dirty_ring_push(&vcpu->dirty_ring,
                                            slot, rel_gfn);
                else
                        set_bit_le(rel_gfn, memslot->dirty_bitmap);
        }
}
EXPORT_SYMBOL_GPL(mark_page_dirty_in_slot);

void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_memory_slot *memslot;

        memslot = gfn_to_memslot(kvm, gfn);
        mark_page_dirty_in_slot(kvm, memslot, gfn);
}
EXPORT_SYMBOL_GPL(mark_page_dirty);

void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        struct kvm_memory_slot *memslot;

        memslot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        mark_page_dirty_in_slot(vcpu->kvm, memslot, gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);

void kvm_sigset_activate(struct kvm_vcpu *vcpu)
{
        if (!vcpu->sigset_active)
                return;

        /*
         * This does a lockless modification of ->real_blocked, which is fine
         * because, only current can change ->real_blocked and all readers of
         * ->real_blocked don't care as long ->real_blocked is always a subset
         * of ->blocked.
         */
        sigprocmask(SIG_SETMASK, &vcpu->sigset, &current->real_blocked);
}

void kvm_sigset_deactivate(struct kvm_vcpu *vcpu)
{
        if (!vcpu->sigset_active)
                return;

        sigprocmask(SIG_SETMASK, &current->real_blocked, NULL);
        sigemptyset(&current->real_blocked);
}

static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
{
        unsigned int old, val, grow, grow_start;

        old = val = vcpu->halt_poll_ns;
        grow_start = READ_ONCE(halt_poll_ns_grow_start);
        grow = READ_ONCE(halt_poll_ns_grow);
        if (!grow)
                goto out;

        val *= grow;
        if (val < grow_start)
                val = grow_start;

        if (val > vcpu->kvm->max_halt_poll_ns)
                val = vcpu->kvm->max_halt_poll_ns;

        vcpu->halt_poll_ns = val;
out:
        trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
}

static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
{
        unsigned int old, val, shrink, grow_start;

        old = val = vcpu->halt_poll_ns;
        shrink = READ_ONCE(halt_poll_ns_shrink);
        grow_start = READ_ONCE(halt_poll_ns_grow_start);
        if (shrink == 0)
                val = 0;
        else
                val /= shrink;

        if (val < grow_start)
                val = 0;

        vcpu->halt_poll_ns = val;
        trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
}

static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
{
        int ret = -EINTR;
        int idx = srcu_read_lock(&vcpu->kvm->srcu);

        if (kvm_arch_vcpu_runnable(vcpu)) {
                kvm_make_request(KVM_REQ_UNHALT, vcpu);
                goto out;
        }
        if (kvm_cpu_has_pending_timer(vcpu))
                goto out;
        if (signal_pending(current))
                goto out;
        if (kvm_check_request(KVM_REQ_UNBLOCK, vcpu))
                goto out;

        ret = 0;
out:
        srcu_read_unlock(&vcpu->kvm->srcu, idx);
        return ret;
}

/*
 * Block the vCPU until the vCPU is runnable, an event arrives, or a signal is
 * pending.  This is mostly used when halting a vCPU, but may also be used
 * directly for other vCPU non-runnable states, e.g. x86's Wait-For-SIPI.
 */
bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
        struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
        bool waited = false;

        vcpu->stat.generic.blocking = 1;

        kvm_arch_vcpu_blocking(vcpu);

        prepare_to_rcuwait(wait);
        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);

                if (kvm_vcpu_check_block(vcpu) < 0)
                        break;

                waited = true;
                schedule();
        }
        finish_rcuwait(wait);

        kvm_arch_vcpu_unblocking(vcpu);

        vcpu->stat.generic.blocking = 0;

        return waited;
}

static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
                                          ktime_t end, bool success)
{
        struct kvm_vcpu_stat_generic *stats = &vcpu->stat.generic;
        u64 poll_ns = ktime_to_ns(ktime_sub(end, start));

        ++vcpu->stat.generic.halt_attempted_poll;

        if (success) {
                ++vcpu->stat.generic.halt_successful_poll;

                if (!vcpu_valid_wakeup(vcpu))
                        ++vcpu->stat.generic.halt_poll_invalid;

                stats->halt_poll_success_ns += poll_ns;
                KVM_STATS_LOG_HIST_UPDATE(stats->halt_poll_success_hist, poll_ns);
        } else {
                stats->halt_poll_fail_ns += poll_ns;
                KVM_STATS_LOG_HIST_UPDATE(stats->halt_poll_fail_hist, poll_ns);
        }
}

/*
 * Emulate a vCPU halt condition, e.g. HLT on x86, WFI on arm, etc...  If halt
 * polling is enabled, busy wait for a short time before blocking to avoid the
 * expensive block+unblock sequence if a wake event arrives soon after the vCPU
 * is halted.
 */
void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
{
        bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
        bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
        ktime_t start, cur, poll_end;
        bool waited = false;
        u64 halt_ns;

        start = cur = poll_end = ktime_get();
        if (do_halt_poll) {
                ktime_t stop = ktime_add_ns(start, vcpu->halt_poll_ns);

                do {
                        /*
                         * This sets KVM_REQ_UNHALT if an interrupt
                         * arrives.
                         */
                        if (kvm_vcpu_check_block(vcpu) < 0)
                                goto out;
                        cpu_relax();
                        poll_end = cur = ktime_get();
                } while (kvm_vcpu_can_poll(cur, stop));
        }

        waited = kvm_vcpu_block(vcpu);

        cur = ktime_get();
        if (waited) {
                vcpu->stat.generic.halt_wait_ns +=
                        ktime_to_ns(cur) - ktime_to_ns(poll_end);
                KVM_STATS_LOG_HIST_UPDATE(vcpu->stat.generic.halt_wait_hist,
                                ktime_to_ns(cur) - ktime_to_ns(poll_end));
        }
out:
        /* The total time the vCPU was "halted", including polling time. */
        halt_ns = ktime_to_ns(cur) - ktime_to_ns(start);

        /*
         * Note, halt-polling is considered successful so long as the vCPU was
         * never actually scheduled out, i.e. even if the wake event arrived
         * after of the halt-polling loop itself, but before the full wait.
         */
        if (do_halt_poll)
                update_halt_poll_stats(vcpu, start, poll_end, !waited);

        if (halt_poll_allowed) {
                if (!vcpu_valid_wakeup(vcpu)) {
                        shrink_halt_poll_ns(vcpu);
                } else if (vcpu->kvm->max_halt_poll_ns) {
                        if (halt_ns <= vcpu->halt_poll_ns)
                                ;
                        /* we had a long block, shrink polling */
                        else if (vcpu->halt_poll_ns &&
                                 halt_ns > vcpu->kvm->max_halt_poll_ns)
                                shrink_halt_poll_ns(vcpu);
                        /* we had a short halt and our poll time is too small */
                        else if (vcpu->halt_poll_ns < vcpu->kvm->max_halt_poll_ns &&
                                 halt_ns < vcpu->kvm->max_halt_poll_ns)
                                grow_halt_poll_ns(vcpu);
                } else {
                        vcpu->halt_poll_ns = 0;
                }
        }

        trace_kvm_vcpu_wakeup(halt_ns, waited, vcpu_valid_wakeup(vcpu));
}
EXPORT_SYMBOL_GPL(kvm_vcpu_halt);

bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
{
        if (__kvm_vcpu_wake_up(vcpu)) {
                WRITE_ONCE(vcpu->ready, true);
                ++vcpu->stat.generic.halt_wakeup;
                return true;
        }

        return false;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_wake_up);

#ifndef CONFIG_S390
/*
 * Kick a sleeping VCPU, or a guest VCPU in guest mode, into host kernel mode.
 */
void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
        int me, cpu;

        if (kvm_vcpu_wake_up(vcpu))
                return;

        me = get_cpu();
        /*
         * The only state change done outside the vcpu mutex is IN_GUEST_MODE
         * to EXITING_GUEST_MODE.  Therefore the moderately expensive "should
         * kick" check does not need atomic operations if kvm_vcpu_kick is used
         * within the vCPU thread itself.
         */
        if (vcpu == __this_cpu_read(kvm_running_vcpu)) {
                if (vcpu->mode == IN_GUEST_MODE)
                        WRITE_ONCE(vcpu->mode, EXITING_GUEST_MODE);
                goto out;
        }

        /*
         * Note, the vCPU could get migrated to a different pCPU at any point
         * after kvm_arch_vcpu_should_kick(), which could result in sending an
         * IPI to the previous pCPU.  But, that's ok because the purpose of the
         * IPI is to force the vCPU to leave IN_GUEST_MODE, and migrating the
         * vCPU also requires it to leave IN_GUEST_MODE.
         */
        if (kvm_arch_vcpu_should_kick(vcpu)) {
                cpu = READ_ONCE(vcpu->cpu);
                if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
                        smp_send_reschedule(cpu);
        }
out:
        put_cpu();
}
EXPORT_SYMBOL_GPL(kvm_vcpu_kick);
#endif /* !CONFIG_S390 */

int kvm_vcpu_yield_to(struct kvm_vcpu *target)
{
        struct pid *pid;
        struct task_struct *task = NULL;
        int ret = 0;

        rcu_read_lock();
        pid = rcu_dereference(target->pid);
        if (pid)
                task = get_pid_task(pid, PIDTYPE_PID);
        rcu_read_unlock();
        if (!task)
                return ret;
        ret = yield_to(task, 1);
        put_task_struct(task);

        return ret;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_yield_to);

/*
 * Helper that checks whether a VCPU is eligible for directed yield.
 * Most eligible candidate to yield is decided by following heuristics:
 *
 *  (a) VCPU which has not done pl-exit or cpu relax intercepted recently
 *  (preempted lock holder), indicated by @in_spin_loop.
 *  Set at the beginning and cleared at the end of interception/PLE handler.
 *
 *  (b) VCPU which has done pl-exit/ cpu relax intercepted but did not get
 *  chance last time (mostly it has become eligible now since we have probably
 *  yielded to lockholder in last iteration. This is done by toggling
 *  @dy_eligible each time a VCPU checked for eligibility.)
 *
 *  Yielding to a recently pl-exited/cpu relax intercepted VCPU before yielding
 *  to preempted lock-holder could result in wrong VCPU selection and CPU
 *  burning. Giving priority for a potential lock-holder increases lock
 *  progress.
 *
 *  Since algorithm is based on heuristics, accessing another VCPU data without
 *  locking does not harm. It may result in trying to yield to  same VCPU, fail
 *  and continue with next VCPU and so on.
 */
static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
        bool eligible;

        eligible = !vcpu->spin_loop.in_spin_loop ||
                    vcpu->spin_loop.dy_eligible;

        if (vcpu->spin_loop.in_spin_loop)
                kvm_vcpu_set_dy_eligible(vcpu, !vcpu->spin_loop.dy_eligible);

        return eligible;
#else
        return true;
#endif
}

/*
 * Unlike kvm_arch_vcpu_runnable, this function is called outside
 * a vcpu_load/vcpu_put pair.  However, for most architectures
 * kvm_arch_vcpu_runnable does not require vcpu_load.
 */
bool __weak kvm_arch_dy_runnable(struct kvm_vcpu *vcpu)
{
        return kvm_arch_vcpu_runnable(vcpu);
}

static bool vcpu_dy_runnable(struct kvm_vcpu *vcpu)
{
        if (kvm_arch_dy_runnable(vcpu))
                return true;

#ifdef CONFIG_KVM_ASYNC_PF
        if (!list_empty_careful(&vcpu->async_pf.done))
                return true;
#endif

        return false;
}

bool __weak kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu)
{
        return false;
}

void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
{
        struct kvm *kvm = me->kvm;
        struct kvm_vcpu *vcpu;
        int last_boosted_vcpu = me->kvm->last_boosted_vcpu;
        unsigned long i;
        int yielded = 0;
        int try = 3;
        int pass;

        kvm_vcpu_set_in_spin_loop(me, true);
        /*
         * We boost the priority of a VCPU that is runnable but not
         * currently running, because it got preempted by something
         * else and called schedule in __vcpu_run.  Hopefully that
         * VCPU is holding the lock that we need and will release it.
         * We approximate round-robin by starting at the last boosted VCPU.
         */
        for (pass = 0; pass < 2 && !yielded && try; pass++) {
                kvm_for_each_vcpu(i, vcpu, kvm) {
                        if (!pass && i <= last_boosted_vcpu) {
                                i = last_boosted_vcpu;
                                continue;
                        } else if (pass && i > last_boosted_vcpu)
                                break;
                        if (!READ_ONCE(vcpu->ready))
                                continue;
                        if (vcpu == me)
                                continue;
                        if (kvm_vcpu_is_blocking(vcpu) && !vcpu_dy_runnable(vcpu))
                                continue;
                        if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
                            !kvm_arch_dy_has_pending_interrupt(vcpu) &&
                            !kvm_arch_vcpu_in_kernel(vcpu))
                                continue;
                        if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
                                continue;

                        yielded = kvm_vcpu_yield_to(vcpu);
                        if (yielded > 0) {
                                kvm->last_boosted_vcpu = i;
                                break;
                        } else if (yielded < 0) {
                                try--;
                                if (!try)
                                        break;
                        }
                }
        }
        kvm_vcpu_set_in_spin_loop(me, false);

        /* Ensure vcpu is not eligible during next spinloop */
        kvm_vcpu_set_dy_eligible(me, false);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);

static bool kvm_page_in_dirty_ring(struct kvm *kvm, unsigned long pgoff)
{
#ifdef CONFIG_HAVE_KVM_DIRTY_RING
        return (pgoff >= KVM_DIRTY_LOG_PAGE_OFFSET) &&
            (pgoff < KVM_DIRTY_LOG_PAGE_OFFSET +
             kvm->dirty_ring_size / PAGE_SIZE);
#else
        return false;
#endif
}

static vm_fault_t kvm_vcpu_fault(struct vm_fault *vmf)
{
        struct kvm_vcpu *vcpu = vmf->vma->vm_file->private_data;
        struct page *page;

        if (vmf->pgoff == 0)
                page = virt_to_page(vcpu->run);
#ifdef CONFIG_X86
        else if (vmf->pgoff == KVM_PIO_PAGE_OFFSET)
                page = virt_to_page(vcpu->arch.pio_data);
#endif
#ifdef CONFIG_KVM_MMIO
        else if (vmf->pgoff == KVM_COALESCED_MMIO_PAGE_OFFSET)
                page = virt_to_page(vcpu->kvm->coalesced_mmio_ring);
#endif
        else if (kvm_page_in_dirty_ring(vcpu->kvm, vmf->pgoff))
                page = kvm_dirty_ring_get_page(
                    &vcpu->dirty_ring,
                    vmf->pgoff - KVM_DIRTY_LOG_PAGE_OFFSET);
        else
                return kvm_arch_vcpu_fault(vcpu, vmf);
        get_page(page);
        vmf->page = page;
        return 0;
}

static const struct vm_operations_struct kvm_vcpu_vm_ops = {
        .fault = kvm_vcpu_fault,
};

static int kvm_vcpu_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct kvm_vcpu *vcpu = file->private_data;
        unsigned long pages = vma_pages(vma);

        if ((kvm_page_in_dirty_ring(vcpu->kvm, vma->vm_pgoff) ||
             kvm_page_in_dirty_ring(vcpu->kvm, vma->vm_pgoff + pages - 1)) &&
            ((vma->vm_flags & VM_EXEC) || !(vma->vm_flags & VM_SHARED)))
                return -EINVAL;

        vma->vm_ops = &kvm_vcpu_vm_ops;
        return 0;
}

static int kvm_vcpu_release(struct inode *inode, struct file *filp)
{
        struct kvm_vcpu *vcpu = filp->private_data;

        kvm_put_kvm(vcpu->kvm);
        return 0;
}

static const struct file_operations kvm_vcpu_fops = {
        .release        = kvm_vcpu_release,
        .unlocked_ioctl = kvm_vcpu_ioctl,
        .mmap           = kvm_vcpu_mmap,
        .llseek         = noop_llseek,
        KVM_COMPAT(kvm_vcpu_compat_ioctl),
};

/*
 * Allocates an inode for the vcpu.
 */
static int create_vcpu_fd(struct kvm_vcpu *vcpu)
{
        char name[8 + 1 + ITOA_MAX_LEN + 1];

        snprintf(name, sizeof(name), "kvm-vcpu:%d", vcpu->vcpu_id);
        return anon_inode_getfd(name, &kvm_vcpu_fops, vcpu, O_RDWR | O_CLOEXEC);
}

static void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
{
#ifdef __KVM_HAVE_ARCH_VCPU_DEBUGFS
        struct dentry *debugfs_dentry;
        char dir_name[ITOA_MAX_LEN * 2];

        if (!debugfs_initialized())
                return;

        snprintf(dir_name, sizeof(dir_name), "vcpu%d", vcpu->vcpu_id);
        debugfs_dentry = debugfs_create_dir(dir_name,
                                            vcpu->kvm->debugfs_dentry);

        kvm_arch_create_vcpu_debugfs(vcpu, debugfs_dentry);
#endif
}

/*
 * Creates some virtual cpus.  Good luck creating more than one.
 */
static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
{
        int r;
        struct kvm_vcpu *vcpu;
        struct page *page;

        if (id >= KVM_MAX_VCPU_IDS)
                return -EINVAL;

        mutex_lock(&kvm->lock);
        if (kvm->created_vcpus == KVM_MAX_VCPUS) {
                mutex_unlock(&kvm->lock);
                return -EINVAL;
        }

        kvm->created_vcpus++;
        mutex_unlock(&kvm->lock);

        r = kvm_arch_vcpu_precreate(kvm, id);
        if (r)
                goto vcpu_decrement;

        vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL_ACCOUNT);
        if (!vcpu) {
                r = -ENOMEM;
                goto vcpu_decrement;
        }

        BUILD_BUG_ON(sizeof(struct kvm_run) > PAGE_SIZE);
        page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
        if (!page) {
                r = -ENOMEM;
                goto vcpu_free;
        }
        vcpu->run = page_address(page);

        kvm_vcpu_init(vcpu, kvm, id);

        r = kvm_arch_vcpu_create(vcpu);
        if (r)
                goto vcpu_free_run_page;

        if (kvm->dirty_ring_size) {
                r = kvm_dirty_ring_alloc(&vcpu->dirty_ring,
                                         id, kvm->dirty_ring_size);
                if (r)
                        goto arch_vcpu_destroy;
        }

        mutex_lock(&kvm->lock);
        if (kvm_get_vcpu_by_id(kvm, id)) {
                r = -EEXIST;
                goto unlock_vcpu_destroy;
        }

        vcpu->vcpu_idx = atomic_read(&kvm->online_vcpus);
        r = xa_insert(&kvm->vcpu_array, vcpu->vcpu_idx, vcpu, GFP_KERNEL_ACCOUNT);
        BUG_ON(r == -EBUSY);
        if (r)
                goto unlock_vcpu_destroy;

        /* Fill the stats id string for the vcpu */
        snprintf(vcpu->stats_id, sizeof(vcpu->stats_id), "kvm-%d/vcpu-%d",
                 task_pid_nr(current), id);

        /* Now it's all set up, let userspace reach it */
        kvm_get_kvm(kvm);
        r = create_vcpu_fd(vcpu);
        if (r < 0) {
                xa_erase(&kvm->vcpu_array, vcpu->vcpu_idx);
                kvm_put_kvm_no_destroy(kvm);
                goto unlock_vcpu_destroy;
        }

        /*
         * Pairs with smp_rmb() in kvm_get_vcpu.  Store the vcpu
         * pointer before kvm->online_vcpu's incremented value.
         */
        smp_wmb();
        atomic_inc(&kvm->online_vcpus);

        mutex_unlock(&kvm->lock);
        kvm_arch_vcpu_postcreate(vcpu);
        kvm_create_vcpu_debugfs(vcpu);
        return r;

unlock_vcpu_destroy:
        mutex_unlock(&kvm->lock);
        kvm_dirty_ring_free(&vcpu->dirty_ring);
arch_vcpu_destroy:
        kvm_arch_vcpu_destroy(vcpu);
vcpu_free_run_page:
        free_page((unsigned long)vcpu->run);
vcpu_free:
        kmem_cache_free(kvm_vcpu_cache, vcpu);
vcpu_decrement:
        mutex_lock(&kvm->lock);
        kvm->created_vcpus--;
        mutex_unlock(&kvm->lock);
        return r;
}

static int kvm_vcpu_ioctl_set_sigmask(struct kvm_vcpu *vcpu, sigset_t *sigset)
{
        if (sigset) {
                sigdelsetmask(sigset, sigmask(SIGKILL)|sigmask(SIGSTOP));
                vcpu->sigset_active = 1;
                vcpu->sigset = *sigset;
        } else
                vcpu->sigset_active = 0;
        return 0;
}

static ssize_t kvm_vcpu_stats_read(struct file *file, char __user *user_buffer,
                              size_t size, loff_t *offset)
{
        struct kvm_vcpu *vcpu = file->private_data;

        return kvm_stats_read(vcpu->stats_id, &kvm_vcpu_stats_header,
                        &kvm_vcpu_stats_desc[0], &vcpu->stat,
                        sizeof(vcpu->stat), user_buffer, size, offset);
}

static const struct file_operations kvm_vcpu_stats_fops = {
        .read = kvm_vcpu_stats_read,
        .llseek = noop_llseek,
};

static int kvm_vcpu_ioctl_get_stats_fd(struct kvm_vcpu *vcpu)
{
        int fd;
        struct file *file;
        char name[15 + ITOA_MAX_LEN + 1];

        snprintf(name, sizeof(name), "kvm-vcpu-stats:%d", vcpu->vcpu_id);

        fd = get_unused_fd_flags(O_CLOEXEC);
        if (fd < 0)
                return fd;

        file = anon_inode_getfile(name, &kvm_vcpu_stats_fops, vcpu, O_RDONLY);
        if (IS_ERR(file)) {
                put_unused_fd(fd);
                return PTR_ERR(file);
        }
        file->f_mode |= FMODE_PREAD;
        fd_install(fd, file);

        return fd;
}

static long kvm_vcpu_ioctl(struct file *filp,
                           unsigned int ioctl, unsigned long arg)
{
        struct kvm_vcpu *vcpu = filp->private_data;
        void __user *argp = (void __user *)arg;
        int r;
        struct kvm_fpu *fpu = NULL;
        struct kvm_sregs *kvm_sregs = NULL;

        if (vcpu->kvm->mm != current->mm || vcpu->kvm->vm_dead)
                return -EIO;

        if (unlikely(_IOC_TYPE(ioctl) != KVMIO))
                return -EINVAL;

        /*
         * Some architectures have vcpu ioctls that are asynchronous to vcpu
         * execution; mutex_lock() would break them.
         */
        r = kvm_arch_vcpu_async_ioctl(filp, ioctl, arg);
        if (r != -ENOIOCTLCMD)
                return r;

        if (mutex_lock_killable(&vcpu->mutex))
                return -EINTR;
        switch (ioctl) {
        case KVM_RUN: {
                struct pid *oldpid;
                r = -EINVAL;
                if (arg)
                        goto out;
                oldpid = rcu_access_pointer(vcpu->pid);
                if (unlikely(oldpid != task_pid(current))) {
                        /* The thread running this VCPU changed. */
                        struct pid *newpid;

                        r = kvm_arch_vcpu_run_pid_change(vcpu);
                        if (r)
                                break;

                        newpid = get_task_pid(current, PIDTYPE_PID);
                        rcu_assign_pointer(vcpu->pid, newpid);
                        if (oldpid)
                                synchronize_rcu();
                        put_pid(oldpid);
                }
                r = kvm_arch_vcpu_ioctl_run(vcpu);
                trace_kvm_userspace_exit(vcpu->run->exit_reason, r);
                break;
        }
        case KVM_GET_REGS: {
                struct kvm_regs *kvm_regs;

                r = -ENOMEM;
                kvm_regs = kzalloc(sizeof(struct kvm_regs), GFP_KERNEL_ACCOUNT);
                if (!kvm_regs)
                        goto out;
                r = kvm_arch_vcpu_ioctl_get_regs(vcpu, kvm_regs);
                if (r)
                        goto out_free1;
                r = -EFAULT;
                if (copy_to_user(argp, kvm_regs, sizeof(struct kvm_regs)))
                        goto out_free1;
                r = 0;
out_free1:
                kfree(kvm_regs);
                break;
        }
        case KVM_SET_REGS: {
                struct kvm_regs *kvm_regs;

                kvm_regs = memdup_user(argp, sizeof(*kvm_regs));
                if (IS_ERR(kvm_regs)) {
                        r = PTR_ERR(kvm_regs);
                        goto out;
                }
                r = kvm_arch_vcpu_ioctl_set_regs(vcpu, kvm_regs);
                kfree(kvm_regs);
                break;
        }
        case KVM_GET_SREGS: {
                kvm_sregs = kzalloc(sizeof(struct kvm_sregs),
                                    GFP_KERNEL_ACCOUNT);
                r = -ENOMEM;
                if (!kvm_sregs)
                        goto out;
                r = kvm_arch_vcpu_ioctl_get_sregs(vcpu, kvm_sregs);
                if (r)
                        goto out;
                r = -EFAULT;
                if (copy_to_user(argp, kvm_sregs, sizeof(struct kvm_sregs)))
                        goto out;
                r = 0;
                break;
        }
        case KVM_SET_SREGS: {
                kvm_sregs = memdup_user(argp, sizeof(*kvm_sregs));
                if (IS_ERR(kvm_sregs)) {
                        r = PTR_ERR(kvm_sregs);
                        kvm_sregs = NULL;
                        goto out;
                }
                r = kvm_arch_vcpu_ioctl_set_sregs(vcpu, kvm_sregs);
                break;
        }
        case KVM_GET_MP_STATE: {
                struct kvm_mp_state mp_state;

                r = kvm_arch_vcpu_ioctl_get_mpstate(vcpu, &mp_state);
                if (r)
                        goto out;
                r = -EFAULT;
                if (copy_to_user(argp, &mp_state, sizeof(mp_state)))
                        goto out;
                r = 0;
                break;
        }
        case KVM_SET_MP_STATE: {
                struct kvm_mp_state mp_state;

                r = -EFAULT;
                if (copy_from_user(&mp_state, argp, sizeof(mp_state)))
                        goto out;
                r = kvm_arch_vcpu_ioctl_set_mpstate(vcpu, &mp_state);
                break;
        }
        case KVM_TRANSLATE: {
                struct kvm_translation tr;

                r = -EFAULT;
                if (copy_from_user(&tr, argp, sizeof(tr)))
                        goto out;
                r = kvm_arch_vcpu_ioctl_translate(vcpu, &tr);
                if (r)
                        goto out;
                r = -EFAULT;
                if (copy_to_user(argp, &tr, sizeof(tr)))
                        goto out;
                r = 0;
                break;
        }
        case KVM_SET_GUEST_DEBUG: {
                struct kvm_guest_debug dbg;

                r = -EFAULT;
                if (copy_from_user(&dbg, argp, sizeof(dbg)))
                        goto out;
                r = kvm_arch_vcpu_ioctl_set_guest_debug(vcpu, &dbg);
                break;
        }
        case KVM_SET_SIGNAL_MASK: {
                struct kvm_signal_mask __user *sigmask_arg = argp;
                struct kvm_signal_mask kvm_sigmask;
                sigset_t sigset, *p;

                p = NULL;
                if (argp) {
                        r = -EFAULT;
                        if (copy_from_user(&kvm_sigmask, argp,
                                           sizeof(kvm_sigmask)))
                                goto out;
                        r = -EINVAL;
                        if (kvm_sigmask.len != sizeof(sigset))
                                goto out;
                        r = -EFAULT;
                        if (copy_from_user(&sigset, sigmask_arg->sigset,
                                           sizeof(sigset)))
                                goto out;
                        p = &sigset;
                }
                r = kvm_vcpu_ioctl_set_sigmask(vcpu, p);
                break;
        }
        case KVM_GET_FPU: {
                fpu = kzalloc(sizeof(struct kvm_fpu), GFP_KERNEL_ACCOUNT);
                r = -ENOMEM;
                if (!fpu)
                        goto out;
                r = kvm_arch_vcpu_ioctl_get_fpu(vcpu, fpu);
                if (r)
                        goto out;
                r = -EFAULT;
                if (copy_to_user(argp, fpu, sizeof(struct kvm_fpu)))
                        goto out;
                r = 0;
                break;
        }
        case KVM_SET_FPU: {
                fpu = memdup_user(argp, sizeof(*fpu));
                if (IS_ERR(fpu)) {
                        r = PTR_ERR(fpu);
                        fpu = NULL;
                        goto out;
                }
                r = kvm_arch_vcpu_ioctl_set_fpu(vcpu, fpu);
                break;
        }
        case KVM_GET_STATS_FD: {
                r = kvm_vcpu_ioctl_get_stats_fd(vcpu);
                break;
        }
        default:
                r = kvm_arch_vcpu_ioctl(filp, ioctl, arg);
        }
out:
        mutex_unlock(&vcpu->mutex);
        kfree(fpu);
        kfree(kvm_sregs);
        return r;
}

#ifdef CONFIG_KVM_COMPAT
static long kvm_vcpu_compat_ioctl(struct file *filp,
                                  unsigned int ioctl, unsigned long arg)
{
        struct kvm_vcpu *vcpu = filp->private_data;
        void __user *argp = compat_ptr(arg);
        int r;

        if (vcpu->kvm->mm != current->mm || vcpu->kvm->vm_dead)
                return -EIO;

        switch (ioctl) {
        case KVM_SET_SIGNAL_MASK: {
                struct kvm_signal_mask __user *sigmask_arg = argp;
                struct kvm_signal_mask kvm_sigmask;
                sigset_t sigset;

                if (argp) {
                        r = -EFAULT;
                        if (copy_from_user(&kvm_sigmask, argp,
                                           sizeof(kvm_sigmask)))
                                goto out;
                        r = -EINVAL;
                        if (kvm_sigmask.len != sizeof(compat_sigset_t))
                                goto out;
                        r = -EFAULT;
                        if (get_compat_sigset(&sigset,
                                              (compat_sigset_t __user *)sigmask_arg->sigset))
                                goto out;
                        r = kvm_vcpu_ioctl_set_sigmask(vcpu, &sigset);
                } else
                        r = kvm_vcpu_ioctl_set_sigmask(vcpu, NULL);
                break;
        }
        default:
                r = kvm_vcpu_ioctl(filp, ioctl, arg);
        }

out:
        return r;
}
#endif

static int kvm_device_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct kvm_device *dev = filp->private_data;

        if (dev->ops->mmap)
                return dev->ops->mmap(dev, vma);

        return -ENODEV;
}

static int kvm_device_ioctl_attr(struct kvm_device *dev,
                                 int (*accessor)(struct kvm_device *dev,
                                                 struct kvm_device_attr *attr),
                                 unsigned long arg)
{
        struct kvm_device_attr attr;

        if (!accessor)
                return -EPERM;

        if (copy_from_user(&attr, (void __user *)arg, sizeof(attr)))
                return -EFAULT;

        return accessor(dev, &attr);
}

static long kvm_device_ioctl(struct file *filp, unsigned int ioctl,
                             unsigned long arg)
{
        struct kvm_device *dev = filp->private_data;

        if (dev->kvm->mm != current->mm || dev->kvm->vm_dead)
                return -EIO;

        switch (ioctl) {
        case KVM_SET_DEVICE_ATTR:
                return kvm_device_ioctl_attr(dev, dev->ops->set_attr, arg);
        case KVM_GET_DEVICE_ATTR:
                return kvm_device_ioctl_attr(dev, dev->ops->get_attr, arg);
        case KVM_HAS_DEVICE_ATTR:
                return kvm_device_ioctl_attr(dev, dev->ops->has_attr, arg);
        default:
                if (dev->ops->ioctl)
                        return dev->ops->ioctl(dev, ioctl, arg);

                return -ENOTTY;
        }
}

static int kvm_device_release(struct inode *inode, struct file *filp)
{
        struct kvm_device *dev = filp->private_data;
        struct kvm *kvm = dev->kvm;

        if (dev->ops->release) {
                mutex_lock(&kvm->lock);
                list_del(&dev->vm_node);
                dev->ops->release(dev);
                mutex_unlock(&kvm->lock);
        }

        kvm_put_kvm(kvm);
        return 0;
}

static const struct file_operations kvm_device_fops = {
        .unlocked_ioctl = kvm_device_ioctl,
        .release = kvm_device_release,
        KVM_COMPAT(kvm_device_ioctl),
        .mmap = kvm_device_mmap,
};

struct kvm_device *kvm_device_from_filp(struct file *filp)
{
        if (filp->f_op != &kvm_device_fops)
                return NULL;

        return filp->private_data;
}

static const struct kvm_device_ops *kvm_device_ops_table[KVM_DEV_TYPE_MAX] = {
#ifdef CONFIG_KVM_MPIC
        [KVM_DEV_TYPE_FSL_MPIC_20]      = &kvm_mpic_ops,
        [KVM_DEV_TYPE_FSL_MPIC_42]      = &kvm_mpic_ops,
#endif
};

int kvm_register_device_ops(const struct kvm_device_ops *ops, u32 type)
{
        if (type >= ARRAY_SIZE(kvm_device_ops_table))
                return -ENOSPC;

        if (kvm_device_ops_table[type] != NULL)
                return -EEXIST;

        kvm_device_ops_table[type] = ops;
        return 0;
}

void kvm_unregister_device_ops(u32 type)
{
        if (kvm_device_ops_table[type] != NULL)
                kvm_device_ops_table[type] = NULL;
}

static int kvm_ioctl_create_device(struct kvm *kvm,
                                   struct kvm_create_device *cd)
{
        const struct kvm_device_ops *ops = NULL;
        struct kvm_device *dev;
        bool test = cd->flags & KVM_CREATE_DEVICE_TEST;
        int type;
        int ret;

        if (cd->type >= ARRAY_SIZE(kvm_device_ops_table))
                return -ENODEV;

        type = array_index_nospec(cd->type, ARRAY_SIZE(kvm_device_ops_table));
        ops = kvm_device_ops_table[type];
        if (ops == NULL)
                return -ENODEV;

        if (test)
                return 0;

        dev = kzalloc(sizeof(*dev), GFP_KERNEL_ACCOUNT);
        if (!dev)
                return -ENOMEM;

        dev->ops = ops;
        dev->kvm = kvm;

        mutex_lock(&kvm->lock);
        ret = ops->create(dev, type);
        if (ret < 0) {
                mutex_unlock(&kvm->lock);
                kfree(dev);
                return ret;
        }
        list_add(&dev->vm_node, &kvm->devices);
        mutex_unlock(&kvm->lock);

        if (ops->init)
                ops->init(dev);

        kvm_get_kvm(kvm);
        ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR | O_CLOEXEC);
        if (ret < 0) {
                kvm_put_kvm_no_destroy(kvm);
                mutex_lock(&kvm->lock);
                list_del(&dev->vm_node);
                mutex_unlock(&kvm->lock);
                ops->destroy(dev);
                return ret;
        }

        cd->fd = ret;
        return 0;
}

static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
{
        switch (arg) {
        case KVM_CAP_USER_MEMORY:
        case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
        case KVM_CAP_JOIN_MEMORY_REGIONS_WORKS:
        case KVM_CAP_INTERNAL_ERROR_DATA:
#ifdef CONFIG_HAVE_KVM_MSI
        case KVM_CAP_SIGNAL_MSI:
#endif
#ifdef CONFIG_HAVE_KVM_IRQFD
        case KVM_CAP_IRQFD:
        case KVM_CAP_IRQFD_RESAMPLE:
#endif
        case KVM_CAP_IOEVENTFD_ANY_LENGTH:
        case KVM_CAP_CHECK_EXTENSION_VM:
        case KVM_CAP_ENABLE_CAP_VM:
        case KVM_CAP_HALT_POLL:
                return 1;
#ifdef CONFIG_KVM_MMIO
        case KVM_CAP_COALESCED_MMIO:
                return KVM_COALESCED_MMIO_PAGE_OFFSET;
        case KVM_CAP_COALESCED_PIO:
                return 1;
#endif
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
        case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2:
                return KVM_DIRTY_LOG_MANUAL_CAPS;
#endif
#ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
        case KVM_CAP_IRQ_ROUTING:
                return KVM_MAX_IRQ_ROUTES;
#endif
#if KVM_ADDRESS_SPACE_NUM > 1
        case KVM_CAP_MULTI_ADDRESS_SPACE:
                return KVM_ADDRESS_SPACE_NUM;
#endif
        case KVM_CAP_NR_MEMSLOTS:
                return KVM_USER_MEM_SLOTS;
        case KVM_CAP_DIRTY_LOG_RING:
#ifdef CONFIG_HAVE_KVM_DIRTY_RING
                return KVM_DIRTY_RING_MAX_ENTRIES * sizeof(struct kvm_dirty_gfn);
#else
                return 0;
#endif
        case KVM_CAP_BINARY_STATS_FD:
        case KVM_CAP_SYSTEM_EVENT_DATA:
                return 1;
        default:
                break;
        }
        return kvm_vm_ioctl_check_extension(kvm, arg);
}

static int kvm_vm_ioctl_enable_dirty_log_ring(struct kvm *kvm, u32 size)
{
        int r;

        if (!KVM_DIRTY_LOG_PAGE_OFFSET)
                return -EINVAL;

        /* the size should be power of 2 */
        if (!size || (size & (size - 1)))
                return -EINVAL;

        /* Should be bigger to keep the reserved entries, or a page */
        if (size < kvm_dirty_ring_get_rsvd_entries() *
            sizeof(struct kvm_dirty_gfn) || size < PAGE_SIZE)
                return -EINVAL;

        if (size > KVM_DIRTY_RING_MAX_ENTRIES *
            sizeof(struct kvm_dirty_gfn))
                return -E2BIG;

        /* We only allow it to set once */
        if (kvm->dirty_ring_size)
                return -EINVAL;

        mutex_lock(&kvm->lock);

        if (kvm->created_vcpus) {
                /* We don't allow to change this value after vcpu created */
                r = -EINVAL;
        } else {
                kvm->dirty_ring_size = size;
                r = 0;
        }

        mutex_unlock(&kvm->lock);
        return r;
}

static int kvm_vm_ioctl_reset_dirty_pages(struct kvm *kvm)
{
        unsigned long i;
        struct kvm_vcpu *vcpu;
        int cleared = 0;

        if (!kvm->dirty_ring_size)
                return -EINVAL;

        mutex_lock(&kvm->slots_lock);

        kvm_for_each_vcpu(i, vcpu, kvm)
                cleared += kvm_dirty_ring_reset(vcpu->kvm, &vcpu->dirty_ring);

        mutex_unlock(&kvm->slots_lock);

        if (cleared)
                kvm_flush_remote_tlbs(kvm);

        return cleared;
}

int __attribute__((weak)) kvm_vm_ioctl_enable_cap(struct kvm *kvm,
                                                  struct kvm_enable_cap *cap)
{
        return -EINVAL;
}

static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
                                           struct kvm_enable_cap *cap)
{
        switch (cap->cap) {
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
        case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: {
                u64 allowed_options = KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE;

                if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE)
                        allowed_options = KVM_DIRTY_LOG_MANUAL_CAPS;

                if (cap->flags || (cap->args[0] & ~allowed_options))
                        return -EINVAL;
                kvm->manual_dirty_log_protect = cap->args[0];
                return 0;
        }
#endif
        case KVM_CAP_HALT_POLL: {
                if (cap->flags || cap->args[0] != (unsigned int)cap->args[0])
                        return -EINVAL;

                kvm->max_halt_poll_ns = cap->args[0];
                return 0;
        }
        case KVM_CAP_DIRTY_LOG_RING:
                return kvm_vm_ioctl_enable_dirty_log_ring(kvm, cap->args[0]);
        default:
                return kvm_vm_ioctl_enable_cap(kvm, cap);
        }
}

static ssize_t kvm_vm_stats_read(struct file *file, char __user *user_buffer,
                              size_t size, loff_t *offset)
{
        struct kvm *kvm = file->private_data;

        return kvm_stats_read(kvm->stats_id, &kvm_vm_stats_header,
                                &kvm_vm_stats_desc[0], &kvm->stat,
                                sizeof(kvm->stat), user_buffer, size, offset);
}

static const struct file_operations kvm_vm_stats_fops = {
        .read = kvm_vm_stats_read,
        .llseek = noop_llseek,
};

static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
{
        int fd;
        struct file *file;

        fd = get_unused_fd_flags(O_CLOEXEC);
        if (fd < 0)
                return fd;

        file = anon_inode_getfile("kvm-vm-stats",
                        &kvm_vm_stats_fops, kvm, O_RDONLY);
        if (IS_ERR(file)) {
                put_unused_fd(fd);
                return PTR_ERR(file);
        }
        file->f_mode |= FMODE_PREAD;
        fd_install(fd, file);

        return fd;
}

static long kvm_vm_ioctl(struct file *filp,
                           unsigned int ioctl, unsigned long arg)
{
        struct kvm *kvm = filp->private_data;
        void __user *argp = (void __user *)arg;
        int r;

        if (kvm->mm != current->mm || kvm->vm_dead)
                return -EIO;
        switch (ioctl) {
        case KVM_CREATE_VCPU:
                r = kvm_vm_ioctl_create_vcpu(kvm, arg);
                break;
        case KVM_ENABLE_CAP: {
                struct kvm_enable_cap cap;

                r = -EFAULT;
                if (copy_from_user(&cap, argp, sizeof(cap)))
                        goto out;
                r = kvm_vm_ioctl_enable_cap_generic(kvm, &cap);
                break;
        }
        case KVM_SET_USER_MEMORY_REGION: {
                struct kvm_userspace_memory_region kvm_userspace_mem;

                r = -EFAULT;
                if (copy_from_user(&kvm_userspace_mem, argp,
                                                sizeof(kvm_userspace_mem)))
                        goto out;

                r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem);
                break;
        }
        case KVM_GET_DIRTY_LOG: {
                struct kvm_dirty_log log;

                r = -EFAULT;
                if (copy_from_user(&log, argp, sizeof(log)))
                        goto out;
                r = kvm_vm_ioctl_get_dirty_log(kvm, &log);
                break;
        }
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
        case KVM_CLEAR_DIRTY_LOG: {
                struct kvm_clear_dirty_log log;

                r = -EFAULT;
                if (copy_from_user(&log, argp, sizeof(log)))
                        goto out;
                r = kvm_vm_ioctl_clear_dirty_log(kvm, &log);
                break;
        }
#endif
#ifdef CONFIG_KVM_MMIO
        case KVM_REGISTER_COALESCED_MMIO: {
                struct kvm_coalesced_mmio_zone zone;

                r = -EFAULT;
                if (copy_from_user(&zone, argp, sizeof(zone)))
                        goto out;
                r = kvm_vm_ioctl_register_coalesced_mmio(kvm, &zone);
                break;
        }
        case KVM_UNREGISTER_COALESCED_MMIO: {
                struct kvm_coalesced_mmio_zone zone;

                r = -EFAULT;
                if (copy_from_user(&zone, argp, sizeof(zone)))
                        goto out;
                r = kvm_vm_ioctl_unregister_coalesced_mmio(kvm, &zone);
                break;
        }
#endif
        case KVM_IRQFD: {
                struct kvm_irqfd data;

                r = -EFAULT;
                if (copy_from_user(&data, argp, sizeof(data)))
                        goto out;
                r = kvm_irqfd(kvm, &data);
                break;
        }
        case KVM_IOEVENTFD: {
                struct kvm_ioeventfd data;

                r = -EFAULT;
                if (copy_from_user(&data, argp, sizeof(data)))
                        goto out;
                r = kvm_ioeventfd(kvm, &data);
                break;
        }
#ifdef CONFIG_HAVE_KVM_MSI
        case KVM_SIGNAL_MSI: {
                struct kvm_msi msi;

                r = -EFAULT;
                if (copy_from_user(&msi, argp, sizeof(msi)))
                        goto out;
                r = kvm_send_userspace_msi(kvm, &msi);
                break;
        }
#endif
#ifdef __KVM_HAVE_IRQ_LINE
        case KVM_IRQ_LINE_STATUS:
        case KVM_IRQ_LINE: {
                struct kvm_irq_level irq_event;

                r = -EFAULT;
                if (copy_from_user(&irq_event, argp, sizeof(irq_event)))
                        goto out;

                r = kvm_vm_ioctl_irq_line(kvm, &irq_event,
                                        ioctl == KVM_IRQ_LINE_STATUS);
                if (r)
                        goto out;

                r = -EFAULT;
                if (ioctl == KVM_IRQ_LINE_STATUS) {
                        if (copy_to_user(argp, &irq_event, sizeof(irq_event)))
                                goto out;
                }

                r = 0;
                break;
        }
#endif
#ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
        case KVM_SET_GSI_ROUTING: {
                struct kvm_irq_routing routing;
                struct kvm_irq_routing __user *urouting;
                struct kvm_irq_routing_entry *entries = NULL;

                r = -EFAULT;
                if (copy_from_user(&routing, argp, sizeof(routing)))
                        goto out;
                r = -EINVAL;
                if (!kvm_arch_can_set_irq_routing(kvm))
                        goto out;
                if (routing.nr > KVM_MAX_IRQ_ROUTES)
                        goto out;
                if (routing.flags)
                        goto out;
                if (routing.nr) {
                        urouting = argp;
                        entries = vmemdup_user(urouting->entries,
                                               array_size(sizeof(*entries),
                                                          routing.nr));
                        if (IS_ERR(entries)) {
                                r = PTR_ERR(entries);
                                goto out;
                        }
                }
                r = kvm_set_irq_routing(kvm, entries, routing.nr,
                                        routing.flags);
                kvfree(entries);
                break;
        }
#endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */
        case KVM_CREATE_DEVICE: {
                struct kvm_create_device cd;

                r = -EFAULT;
                if (copy_from_user(&cd, argp, sizeof(cd)))
                        goto out;

                r = kvm_ioctl_create_device(kvm, &cd);
                if (r)
                        goto out;

                r = -EFAULT;
                if (copy_to_user(argp, &cd, sizeof(cd)))
                        goto out;

                r = 0;
                break;
        }
        case KVM_CHECK_EXTENSION:
                r = kvm_vm_ioctl_check_extension_generic(kvm, arg);
                break;
        case KVM_RESET_DIRTY_RINGS:
                r = kvm_vm_ioctl_reset_dirty_pages(kvm);
                break;
        case KVM_GET_STATS_FD:
                r = kvm_vm_ioctl_get_stats_fd(kvm);
                break;
        default:
                r = kvm_arch_vm_ioctl(filp, ioctl, arg);
        }
out:
        return r;
}

#ifdef CONFIG_KVM_COMPAT
struct compat_kvm_dirty_log {
        __u32 slot;
        __u32 padding1;
        union {
                compat_uptr_t dirty_bitmap; /* one bit per page */
                __u64 padding2;
        };
};

struct compat_kvm_clear_dirty_log {
        __u32 slot;
        __u32 num_pages;
        __u64 first_page;
        union {
                compat_uptr_t dirty_bitmap; /* one bit per page */
                __u64 padding2;
        };
};

static long kvm_vm_compat_ioctl(struct file *filp,
                           unsigned int ioctl, unsigned long arg)
{
        struct kvm *kvm = filp->private_data;
        int r;

        if (kvm->mm != current->mm || kvm->vm_dead)
                return -EIO;
        switch (ioctl) {
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
        case KVM_CLEAR_DIRTY_LOG: {
                struct compat_kvm_clear_dirty_log compat_log;
                struct kvm_clear_dirty_log log;

                if (copy_from_user(&compat_log, (void __user *)arg,
                                   sizeof(compat_log)))
                        return -EFAULT;
                log.slot         = compat_log.slot;
                log.num_pages    = compat_log.num_pages;
                log.first_page   = compat_log.first_page;
                log.padding2     = compat_log.padding2;
                log.dirty_bitmap = compat_ptr(compat_log.dirty_bitmap);

                r = kvm_vm_ioctl_clear_dirty_log(kvm, &log);
                break;
        }
#endif
        case KVM_GET_DIRTY_LOG: {
                struct compat_kvm_dirty_log compat_log;
                struct kvm_dirty_log log;

                if (copy_from_user(&compat_log, (void __user *)arg,
                                   sizeof(compat_log)))
                        return -EFAULT;
                log.slot         = compat_log.slot;
                log.padding1     = compat_log.padding1;
                log.padding2     = compat_log.padding2;
                log.dirty_bitmap = compat_ptr(compat_log.dirty_bitmap);

                r = kvm_vm_ioctl_get_dirty_log(kvm, &log);
                break;
        }
        default:
                r = kvm_vm_ioctl(filp, ioctl, arg);
        }
        return r;
}
#endif

static const struct file_operations kvm_vm_fops = {
        .release        = kvm_vm_release,
        .unlocked_ioctl = kvm_vm_ioctl,
        .llseek         = noop_llseek,
        KVM_COMPAT(kvm_vm_compat_ioctl),
};

bool file_is_kvm(struct file *file)
{
        return file && file->f_op == &kvm_vm_fops;
}
EXPORT_SYMBOL_GPL(file_is_kvm);

static int kvm_dev_ioctl_create_vm(unsigned long type)
{
        int r;
        struct kvm *kvm;
        struct file *file;

        kvm = kvm_create_vm(type);
        if (IS_ERR(kvm))
                return PTR_ERR(kvm);
#ifdef CONFIG_KVM_MMIO
        r = kvm_coalesced_mmio_init(kvm);
        if (r < 0)
                goto put_kvm;
#endif
        r = get_unused_fd_flags(O_CLOEXEC);
        if (r < 0)
                goto put_kvm;

        snprintf(kvm->stats_id, sizeof(kvm->stats_id),
                        "kvm-%d", task_pid_nr(current));

        file = anon_inode_getfile("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
        if (IS_ERR(file)) {
                put_unused_fd(r);
                r = PTR_ERR(file);
                goto put_kvm;
        }

        /*
         * Don't call kvm_put_kvm anymore at this point; file->f_op is
         * already set, with ->release() being kvm_vm_release().  In error
         * cases it will be called by the final fput(file) and will take
         * care of doing kvm_put_kvm(kvm).
         */
        if (kvm_create_vm_debugfs(kvm, r) < 0) {
                put_unused_fd(r);
                fput(file);
                return -ENOMEM;
        }
        kvm_uevent_notify_change(KVM_EVENT_CREATE_VM, kvm);

        fd_install(r, file);
        return r;

put_kvm:
        kvm_put_kvm(kvm);
        return r;
}

static long kvm_dev_ioctl(struct file *filp,
                          unsigned int ioctl, unsigned long arg)
{
        long r = -EINVAL;

        switch (ioctl) {
        case KVM_GET_API_VERSION:
                if (arg)
                        goto out;
                r = KVM_API_VERSION;
                break;
        case KVM_CREATE_VM:
                r = kvm_dev_ioctl_create_vm(arg);
                break;
        case KVM_CHECK_EXTENSION:
                r = kvm_vm_ioctl_check_extension_generic(NULL, arg);
                break;
        case KVM_GET_VCPU_MMAP_SIZE:
                if (arg)
                        goto out;
                r = PAGE_SIZE;     /* struct kvm_run */
#ifdef CONFIG_X86
                r += PAGE_SIZE;    /* pio data page */
#endif
#ifdef CONFIG_KVM_MMIO
                r += PAGE_SIZE;    /* coalesced mmio ring page */
#endif
                break;
        case KVM_TRACE_ENABLE:
        case KVM_TRACE_PAUSE:
        case KVM_TRACE_DISABLE:
                r = -EOPNOTSUPP;
                break;
        default:
                return kvm_arch_dev_ioctl(filp, ioctl, arg);
        }
out:
        return r;
}

static struct file_operations kvm_chardev_ops = {
        .unlocked_ioctl = kvm_dev_ioctl,
        .llseek         = noop_llseek,
        KVM_COMPAT(kvm_dev_ioctl),
};

static struct miscdevice kvm_dev = {
        KVM_MINOR,
        "kvm",
        &kvm_chardev_ops,
};

static void hardware_enable_nolock(void *junk)
{
        int cpu = raw_smp_processor_id();
        int r;

        if (cpumask_test_cpu(cpu, cpus_hardware_enabled))
                return;

        cpumask_set_cpu(cpu, cpus_hardware_enabled);

        r = kvm_arch_hardware_enable();

        if (r) {
                cpumask_clear_cpu(cpu, cpus_hardware_enabled);
                atomic_inc(&hardware_enable_failed);
                pr_info("kvm: enabling virtualization on CPU%d failed\n", cpu);
        }
}

static int kvm_starting_cpu(unsigned int cpu)
{
        raw_spin_lock(&kvm_count_lock);
        if (kvm_usage_count)
                hardware_enable_nolock(NULL);
        raw_spin_unlock(&kvm_count_lock);
        return 0;
}

static void hardware_disable_nolock(void *junk)
{
        int cpu = raw_smp_processor_id();

        if (!cpumask_test_cpu(cpu, cpus_hardware_enabled))
                return;
        cpumask_clear_cpu(cpu, cpus_hardware_enabled);
        kvm_arch_hardware_disable();
}

static int kvm_dying_cpu(unsigned int cpu)
{
        raw_spin_lock(&kvm_count_lock);
        if (kvm_usage_count)
                hardware_disable_nolock(NULL);
        raw_spin_unlock(&kvm_count_lock);
        return 0;
}

static void hardware_disable_all_nolock(void)
{
        BUG_ON(!kvm_usage_count);

        kvm_usage_count--;
        if (!kvm_usage_count)
                on_each_cpu(hardware_disable_nolock, NULL, 1);
}

static void hardware_disable_all(void)
{
        raw_spin_lock(&kvm_count_lock);
        hardware_disable_all_nolock();
        raw_spin_unlock(&kvm_count_lock);
}

static int hardware_enable_all(void)
{
        int r = 0;

        raw_spin_lock(&kvm_count_lock);

        kvm_usage_count++;
        if (kvm_usage_count == 1) {
                atomic_set(&hardware_enable_failed, 0);
                on_each_cpu(hardware_enable_nolock, NULL, 1);

                if (atomic_read(&hardware_enable_failed)) {
                        hardware_disable_all_nolock();
                        r = -EBUSY;
                }
        }

        raw_spin_unlock(&kvm_count_lock);

        return r;
}

static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
                      void *v)
{
        /*
         * Some (well, at least mine) BIOSes hang on reboot if
         * in vmx root mode.
         *
         * And Intel TXT required VMX off for all cpu when system shutdown.
         */
        pr_info("kvm: exiting hardware virtualization\n");
        kvm_rebooting = true;
        on_each_cpu(hardware_disable_nolock, NULL, 1);
        return NOTIFY_OK;
}

static struct notifier_block kvm_reboot_notifier = {
        .notifier_call = kvm_reboot,
        .priority = 0,
};

static void kvm_io_bus_destroy(struct kvm_io_bus *bus)
{
        int i;

        for (i = 0; i < bus->dev_count; i++) {
                struct kvm_io_device *pos = bus->range[i].dev;

                kvm_iodevice_destructor(pos);
        }
        kfree(bus);
}

static inline int kvm_io_bus_cmp(const struct kvm_io_range *r1,
                                 const struct kvm_io_range *r2)
{
        gpa_t addr1 = r1->addr;
        gpa_t addr2 = r2->addr;

        if (addr1 < addr2)
                return -1;

        /* If r2->len == 0, match the exact address.  If r2->len != 0,
         * accept any overlapping write.  Any order is acceptable for
         * overlapping ranges, because kvm_io_bus_get_first_dev ensures
         * we process all of them.
         */
        if (r2->len) {
                addr1 += r1->len;
                addr2 += r2->len;
        }

        if (addr1 > addr2)
                return 1;

        return 0;
}

static int kvm_io_bus_sort_cmp(const void *p1, const void *p2)
{
        return kvm_io_bus_cmp(p1, p2);
}

static int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus,
                             gpa_t addr, int len)
{
        struct kvm_io_range *range, key;
        int off;

        key = (struct kvm_io_range) {
                .addr = addr,
                .len = len,
        };

        range = bsearch(&key, bus->range, bus->dev_count,
                        sizeof(struct kvm_io_range), kvm_io_bus_sort_cmp);
        if (range == NULL)
                return -ENOENT;

        off = range - bus->range;

        while (off > 0 && kvm_io_bus_cmp(&key, &bus->range[off-1]) == 0)
                off--;

        return off;
}

static int __kvm_io_bus_write(struct kvm_vcpu *vcpu, struct kvm_io_bus *bus,
                              struct kvm_io_range *range, const void *val)
{
        int idx;

        idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
        if (idx < 0)
                return -EOPNOTSUPP;

        while (idx < bus->dev_count &&
                kvm_io_bus_cmp(range, &bus->range[idx]) == 0) {
                if (!kvm_iodevice_write(vcpu, bus->range[idx].dev, range->addr,
                                        range->len, val))
                        return idx;
                idx++;
        }

        return -EOPNOTSUPP;
}

/* kvm_io_bus_write - called under kvm->slots_lock */
int kvm_io_bus_write(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
                     int len, const void *val)
{
        struct kvm_io_bus *bus;
        struct kvm_io_range range;
        int r;

        range = (struct kvm_io_range) {
                .addr = addr,
                .len = len,
        };

        bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
        if (!bus)
                return -ENOMEM;
        r = __kvm_io_bus_write(vcpu, bus, &range, val);
        return r < 0 ? r : 0;
}
EXPORT_SYMBOL_GPL(kvm_io_bus_write);

/* kvm_io_bus_write_cookie - called under kvm->slots_lock */
int kvm_io_bus_write_cookie(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx,
                            gpa_t addr, int len, const void *val, long cookie)
{
        struct kvm_io_bus *bus;
        struct kvm_io_range range;

        range = (struct kvm_io_range) {
                .addr = addr,
                .len = len,
        };

        bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
        if (!bus)
                return -ENOMEM;

        /* First try the device referenced by cookie. */
        if ((cookie >= 0) && (cookie < bus->dev_count) &&
            (kvm_io_bus_cmp(&range, &bus->range[cookie]) == 0))
                if (!kvm_iodevice_write(vcpu, bus->range[cookie].dev, addr, len,
                                        val))
                        return cookie;

        /*
         * cookie contained garbage; fall back to search and return the
         * correct cookie value.
         */
        return __kvm_io_bus_write(vcpu, bus, &range, val);
}

static int __kvm_io_bus_read(struct kvm_vcpu *vcpu, struct kvm_io_bus *bus,
                             struct kvm_io_range *range, void *val)
{
        int idx;

        idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
        if (idx < 0)
                return -EOPNOTSUPP;

        while (idx < bus->dev_count &&
                kvm_io_bus_cmp(range, &bus->range[idx]) == 0) {
                if (!kvm_iodevice_read(vcpu, bus->range[idx].dev, range->addr,
                                       range->len, val))
                        return idx;
                idx++;
        }

        return -EOPNOTSUPP;
}

/* kvm_io_bus_read - called under kvm->slots_lock */
int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
                    int len, void *val)
{
        struct kvm_io_bus *bus;
        struct kvm_io_range range;
        int r;

        range = (struct kvm_io_range) {
                .addr = addr,
                .len = len,
        };

        bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
        if (!bus)
                return -ENOMEM;
        r = __kvm_io_bus_read(vcpu, bus, &range, val);
        return r < 0 ? r : 0;
}

/* Caller must hold slots_lock. */
int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
                            int len, struct kvm_io_device *dev)
{
        int i;
        struct kvm_io_bus *new_bus, *bus;
        struct kvm_io_range range;

        bus = kvm_get_bus(kvm, bus_idx);
        if (!bus)
                return -ENOMEM;

        /* exclude ioeventfd which is limited by maximum fd */
        if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
                return -ENOSPC;

        new_bus = kmalloc(struct_size(bus, range, bus->dev_count + 1),
                          GFP_KERNEL_ACCOUNT);
        if (!new_bus)
                return -ENOMEM;

        range = (struct kvm_io_range) {
                .addr = addr,
                .len = len,
                .dev = dev,
        };

        for (i = 0; i < bus->dev_count; i++)
                if (kvm_io_bus_cmp(&bus->range[i], &range) > 0)
                        break;

        memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
        new_bus->dev_count++;
        new_bus->range[i] = range;
        memcpy(new_bus->range + i + 1, bus->range + i,
                (bus->dev_count - i) * sizeof(struct kvm_io_range));
        rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
        synchronize_srcu_expedited(&kvm->srcu);
        kfree(bus);

        return 0;
}

int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
                              struct kvm_io_device *dev)
{
        int i, j;
        struct kvm_io_bus *new_bus, *bus;

        lockdep_assert_held(&kvm->slots_lock);

        bus = kvm_get_bus(kvm, bus_idx);
        if (!bus)
                return 0;

        for (i = 0; i < bus->dev_count; i++) {
                if (bus->range[i].dev == dev) {
                        break;
                }
        }

        if (i == bus->dev_count)
                return 0;

        new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
                          GFP_KERNEL_ACCOUNT);
        if (new_bus) {
                memcpy(new_bus, bus, struct_size(bus, range, i));
                new_bus->dev_count--;
                memcpy(new_bus->range + i, bus->range + i + 1,
                                flex_array_size(new_bus, range, new_bus->dev_count - i));
        }

        rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
        synchronize_srcu_expedited(&kvm->srcu);

        /* Destroy the old bus _after_ installing the (null) bus. */
        if (!new_bus) {
                pr_err("kvm: failed to shrink bus, removing it completely\n");
                for (j = 0; j < bus->dev_count; j++) {
                        if (j == i)
                                continue;
                        kvm_iodevice_destructor(bus->range[j].dev);
                }
        }

        kfree(bus);
        return new_bus ? 0 : -ENOMEM;
}

struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx,
                                         gpa_t addr)
{
        struct kvm_io_bus *bus;
        int dev_idx, srcu_idx;
        struct kvm_io_device *iodev = NULL;

        srcu_idx = srcu_read_lock(&kvm->srcu);

        bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
        if (!bus)
                goto out_unlock;

        dev_idx = kvm_io_bus_get_first_dev(bus, addr, 1);
        if (dev_idx < 0)
                goto out_unlock;

        iodev = bus->range[dev_idx].dev;

out_unlock:
        srcu_read_unlock(&kvm->srcu, srcu_idx);

        return iodev;
}
EXPORT_SYMBOL_GPL(kvm_io_bus_get_dev);

static int kvm_debugfs_open(struct inode *inode, struct file *file,
                           int (*get)(void *, u64 *), int (*set)(void *, u64),
                           const char *fmt)
{
        struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
                                          inode->i_private;

        /*
         * The debugfs files are a reference to the kvm struct which
        * is still valid when kvm_destroy_vm is called.  kvm_get_kvm_safe
        * avoids the race between open and the removal of the debugfs directory.
         */
        if (!kvm_get_kvm_safe(stat_data->kvm))
                return -ENOENT;

        if (simple_attr_open(inode, file, get,
                    kvm_stats_debugfs_mode(stat_data->desc) & 0222
                    ? set : NULL,
                    fmt)) {
                kvm_put_kvm(stat_data->kvm);
                return -ENOMEM;
        }

        return 0;
}

static int kvm_debugfs_release(struct inode *inode, struct file *file)
{
        struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
                                          inode->i_private;

        simple_attr_release(inode, file);
        kvm_put_kvm(stat_data->kvm);

        return 0;
}

static int kvm_get_stat_per_vm(struct kvm *kvm, size_t offset, u64 *val)
{
        *val = *(u64 *)((void *)(&kvm->stat) + offset);

        return 0;
}

static int kvm_clear_stat_per_vm(struct kvm *kvm, size_t offset)
{
        *(u64 *)((void *)(&kvm->stat) + offset) = 0;

        return 0;
}

static int kvm_get_stat_per_vcpu(struct kvm *kvm, size_t offset, u64 *val)
{
        unsigned long i;
        struct kvm_vcpu *vcpu;

        *val = 0;

        kvm_for_each_vcpu(i, vcpu, kvm)
                *val += *(u64 *)((void *)(&vcpu->stat) + offset);

        return 0;
}

static int kvm_clear_stat_per_vcpu(struct kvm *kvm, size_t offset)
{
        unsigned long i;
        struct kvm_vcpu *vcpu;

        kvm_for_each_vcpu(i, vcpu, kvm)
                *(u64 *)((void *)(&vcpu->stat) + offset) = 0;

        return 0;
}

static int kvm_stat_data_get(void *data, u64 *val)
{
        int r = -EFAULT;
        struct kvm_stat_data *stat_data = (struct kvm_stat_data *)data;

        switch (stat_data->kind) {
        case KVM_STAT_VM:
                r = kvm_get_stat_per_vm(stat_data->kvm,
                                        stat_data->desc->desc.offset, val);
                break;
        case KVM_STAT_VCPU:
                r = kvm_get_stat_per_vcpu(stat_data->kvm,
                                          stat_data->desc->desc.offset, val);
                break;
        }

        return r;
}

static int kvm_stat_data_clear(void *data, u64 val)
{
        int r = -EFAULT;
        struct kvm_stat_data *stat_data = (struct kvm_stat_data *)data;

        if (val)
                return -EINVAL;

        switch (stat_data->kind) {
        case KVM_STAT_VM:
                r = kvm_clear_stat_per_vm(stat_data->kvm,
                                          stat_data->desc->desc.offset);
                break;
        case KVM_STAT_VCPU:
                r = kvm_clear_stat_per_vcpu(stat_data->kvm,
                                            stat_data->desc->desc.offset);
                break;
        }

        return r;
}

static int kvm_stat_data_open(struct inode *inode, struct file *file)
{
        __simple_attr_check_format("%llu\n", 0ull);
        return kvm_debugfs_open(inode, file, kvm_stat_data_get,
                                kvm_stat_data_clear, "%llu\n");
}

static const struct file_operations stat_fops_per_vm = {
        .owner = THIS_MODULE,
        .open = kvm_stat_data_open,
        .release = kvm_debugfs_release,
        .read = simple_attr_read,
        .write = simple_attr_write,
        .llseek = no_llseek,
};

static int vm_stat_get(void *_offset, u64 *val)
{
        unsigned offset = (long)_offset;
        struct kvm *kvm;
        u64 tmp_val;

        *val = 0;
        mutex_lock(&kvm_lock);
        list_for_each_entry(kvm, &vm_list, vm_list) {
                kvm_get_stat_per_vm(kvm, offset, &tmp_val);
                *val += tmp_val;
        }
        mutex_unlock(&kvm_lock);
        return 0;
}

static int vm_stat_clear(void *_offset, u64 val)
{
        unsigned offset = (long)_offset;
        struct kvm *kvm;

        if (val)
                return -EINVAL;

        mutex_lock(&kvm_lock);
        list_for_each_entry(kvm, &vm_list, vm_list) {
                kvm_clear_stat_per_vm(kvm, offset);
        }
        mutex_unlock(&kvm_lock);

        return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(vm_stat_fops, vm_stat_get, vm_stat_clear, "%llu\n");
DEFINE_SIMPLE_ATTRIBUTE(vm_stat_readonly_fops, vm_stat_get, NULL, "%llu\n");

static int vcpu_stat_get(void *_offset, u64 *val)
{
        unsigned offset = (long)_offset;
        struct kvm *kvm;
        u64 tmp_val;

        *val = 0;
        mutex_lock(&kvm_lock);
        list_for_each_entry(kvm, &vm_list, vm_list) {
                kvm_get_stat_per_vcpu(kvm, offset, &tmp_val);
                *val += tmp_val;
        }
        mutex_unlock(&kvm_lock);
        return 0;
}

static int vcpu_stat_clear(void *_offset, u64 val)
{
        unsigned offset = (long)_offset;
        struct kvm *kvm;

        if (val)
                return -EINVAL;

        mutex_lock(&kvm_lock);
        list_for_each_entry(kvm, &vm_list, vm_list) {
                kvm_clear_stat_per_vcpu(kvm, offset);
        }
        mutex_unlock(&kvm_lock);

        return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(vcpu_stat_fops, vcpu_stat_get, vcpu_stat_clear,
                        "%llu\n");
DEFINE_SIMPLE_ATTRIBUTE(vcpu_stat_readonly_fops, vcpu_stat_get, NULL, "%llu\n");

static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
{
        struct kobj_uevent_env *env;
        unsigned long long created, active;

        if (!kvm_dev.this_device || !kvm)
                return;

        mutex_lock(&kvm_lock);
        if (type == KVM_EVENT_CREATE_VM) {
                kvm_createvm_count++;
                kvm_active_vms++;
        } else if (type == KVM_EVENT_DESTROY_VM) {
                kvm_active_vms--;
        }
        created = kvm_createvm_count;
        active = kvm_active_vms;
        mutex_unlock(&kvm_lock);

        env = kzalloc(sizeof(*env), GFP_KERNEL_ACCOUNT);
        if (!env)
                return;

        add_uevent_var(env, "CREATED=%llu", created);
        add_uevent_var(env, "COUNT=%llu", active);

        if (type == KVM_EVENT_CREATE_VM) {
                add_uevent_var(env, "EVENT=create");
                kvm->userspace_pid = task_pid_nr(current);
        } else if (type == KVM_EVENT_DESTROY_VM) {
                add_uevent_var(env, "EVENT=destroy");
        }
        add_uevent_var(env, "PID=%d", kvm->userspace_pid);

        if (!IS_ERR(kvm->debugfs_dentry)) {
                char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL_ACCOUNT);

                if (p) {
                        tmp = dentry_path_raw(kvm->debugfs_dentry, p, PATH_MAX);
                        if (!IS_ERR(tmp))
                                add_uevent_var(env, "STATS_PATH=%s", tmp);
                        kfree(p);
                }
        }
        /* no need for checks, since we are adding at most only 5 keys */
        env->envp[env->envp_idx++] = NULL;
        kobject_uevent_env(&kvm_dev.this_device->kobj, KOBJ_CHANGE, env->envp);
        kfree(env);
}

static void kvm_init_debug(void)
{
        const struct file_operations *fops;
        const struct _kvm_stats_desc *pdesc;
        int i;

        kvm_debugfs_dir = debugfs_create_dir("kvm", NULL);

        for (i = 0; i < kvm_vm_stats_header.num_desc; ++i) {
                pdesc = &kvm_vm_stats_desc[i];
                if (kvm_stats_debugfs_mode(pdesc) & 0222)
                        fops = &vm_stat_fops;
                else
                        fops = &vm_stat_readonly_fops;
                debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
                                kvm_debugfs_dir,
                                (void *)(long)pdesc->desc.offset, fops);
        }

        for (i = 0; i < kvm_vcpu_stats_header.num_desc; ++i) {
                pdesc = &kvm_vcpu_stats_desc[i];
                if (kvm_stats_debugfs_mode(pdesc) & 0222)
                        fops = &vcpu_stat_fops;
                else
                        fops = &vcpu_stat_readonly_fops;
                debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
                                kvm_debugfs_dir,
                                (void *)(long)pdesc->desc.offset, fops);
        }
}

static int kvm_suspend(void)
{
        if (kvm_usage_count)
                hardware_disable_nolock(NULL);
        return 0;
}

static void kvm_resume(void)
{
        if (kvm_usage_count) {
                lockdep_assert_not_held(&kvm_count_lock);
                hardware_enable_nolock(NULL);
        }
}

static struct syscore_ops kvm_syscore_ops = {
        .suspend = kvm_suspend,
        .resume = kvm_resume,
};

static inline
struct kvm_vcpu *preempt_notifier_to_vcpu(struct preempt_notifier *pn)
{
        return container_of(pn, struct kvm_vcpu, preempt_notifier);
}

static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
{
        struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);

        WRITE_ONCE(vcpu->preempted, false);
        WRITE_ONCE(vcpu->ready, false);

        __this_cpu_write(kvm_running_vcpu, vcpu);
        kvm_arch_sched_in(vcpu, cpu);
        kvm_arch_vcpu_load(vcpu, cpu);
}

static void kvm_sched_out(struct preempt_notifier *pn,
                          struct task_struct *next)
{
        struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);

        if (current->on_rq) {
                WRITE_ONCE(vcpu->preempted, true);
                WRITE_ONCE(vcpu->ready, true);
        }
        kvm_arch_vcpu_put(vcpu);
        __this_cpu_write(kvm_running_vcpu, NULL);
}

/**
 * kvm_get_running_vcpu - get the vcpu running on the current CPU.
 *
 * We can disable preemption locally around accessing the per-CPU variable,
 * and use the resolved vcpu pointer after enabling preemption again,
 * because even if the current thread is migrated to another CPU, reading
 * the per-CPU value later will give us the same value as we update the
 * per-CPU variable in the preempt notifier handlers.
 */
struct kvm_vcpu *kvm_get_running_vcpu(void)
{
        struct kvm_vcpu *vcpu;

        preempt_disable();
        vcpu = __this_cpu_read(kvm_running_vcpu);
        preempt_enable();

        return vcpu;
}
EXPORT_SYMBOL_GPL(kvm_get_running_vcpu);

/**
 * kvm_get_running_vcpus - get the per-CPU array of currently running vcpus.
 */
struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
{
        return &kvm_running_vcpu;
}

#ifdef CONFIG_GUEST_PERF_EVENTS
static unsigned int kvm_guest_state(void)
{
        struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
        unsigned int state;

        if (!kvm_arch_pmi_in_guest(vcpu))
                return 0;

        state = PERF_GUEST_ACTIVE;
        if (!kvm_arch_vcpu_in_kernel(vcpu))
                state |= PERF_GUEST_USER;

        return state;
}

static unsigned long kvm_guest_get_ip(void)
{
        struct kvm_vcpu *vcpu = kvm_get_running_vcpu();

        /* Retrieving the IP must be guarded by a call to kvm_guest_state(). */
        if (WARN_ON_ONCE(!kvm_arch_pmi_in_guest(vcpu)))
                return 0;

        return kvm_arch_vcpu_get_ip(vcpu);
}

static struct perf_guest_info_callbacks kvm_guest_cbs = {
        .state                  = kvm_guest_state,
        .get_ip                 = kvm_guest_get_ip,
        .handle_intel_pt_intr   = NULL,
};

void kvm_register_perf_callbacks(unsigned int (*pt_intr_handler)(void))
{
        kvm_guest_cbs.handle_intel_pt_intr = pt_intr_handler;
        perf_register_guest_info_callbacks(&kvm_guest_cbs);
}
void kvm_unregister_perf_callbacks(void)
{
        perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
}
#endif

struct kvm_cpu_compat_check {
        void *opaque;
        int *ret;
};

static void check_processor_compat(void *data)
{
        struct kvm_cpu_compat_check *c = data;

        *c->ret = kvm_arch_check_processor_compat(c->opaque);
}

int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
                  struct module *module)
{
        struct kvm_cpu_compat_check c;
        int r;
        int cpu;

        r = kvm_arch_init(opaque);
        if (r)
                goto out_fail;

        /*
         * kvm_arch_init makes sure there's at most one caller
         * for architectures that support multiple implementations,
         * like intel and amd on x86.
         * kvm_arch_init must be called before kvm_irqfd_init to avoid creating
         * conflicts in case kvm is already setup for another implementation.
         */
        r = kvm_irqfd_init();
        if (r)
                goto out_irqfd;

        if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {
                r = -ENOMEM;
                goto out_free_0;
        }

        r = kvm_arch_hardware_setup(opaque);
        if (r < 0)
                goto out_free_1;

        c.ret = &r;
        c.opaque = opaque;
        for_each_online_cpu(cpu) {
                smp_call_function_single(cpu, check_processor_compat, &c, 1);
                if (r < 0)
                        goto out_free_2;
        }

        r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_STARTING, "kvm/cpu:starting",
                                      kvm_starting_cpu, kvm_dying_cpu);
        if (r)
                goto out_free_2;
        register_reboot_notifier(&kvm_reboot_notifier);

        /* A kmem cache lets us meet the alignment requirements of fx_save. */
        if (!vcpu_align)
                vcpu_align = __alignof__(struct kvm_vcpu);
        kvm_vcpu_cache =
                kmem_cache_create_usercopy("kvm_vcpu", vcpu_size, vcpu_align,
                                           SLAB_ACCOUNT,
                                           offsetof(struct kvm_vcpu, arch),
                                           offsetofend(struct kvm_vcpu, stats_id)
                                           - offsetof(struct kvm_vcpu, arch),
                                           NULL);
        if (!kvm_vcpu_cache) {
                r = -ENOMEM;
                goto out_free_3;
        }

        for_each_possible_cpu(cpu) {
                if (!alloc_cpumask_var_node(&per_cpu(cpu_kick_mask, cpu),
                                            GFP_KERNEL, cpu_to_node(cpu))) {
                        r = -ENOMEM;
                        goto out_free_4;
                }
        }

        r = kvm_async_pf_init();
        if (r)
                goto out_free_5;

        kvm_chardev_ops.owner = module;

        r = misc_register(&kvm_dev);
        if (r) {
                pr_err("kvm: misc device register failed\n");
                goto out_unreg;
        }

        register_syscore_ops(&kvm_syscore_ops);

        kvm_preempt_ops.sched_in = kvm_sched_in;
        kvm_preempt_ops.sched_out = kvm_sched_out;

        kvm_init_debug();

        r = kvm_vfio_ops_init();
        WARN_ON(r);

        return 0;

out_unreg:
        kvm_async_pf_deinit();
out_free_5:
        for_each_possible_cpu(cpu)
                free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
out_free_4:
        kmem_cache_destroy(kvm_vcpu_cache);
out_free_3:
        unregister_reboot_notifier(&kvm_reboot_notifier);
        cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
out_free_2:
        kvm_arch_hardware_unsetup();
out_free_1:
        free_cpumask_var(cpus_hardware_enabled);
out_free_0:
        kvm_irqfd_exit();
out_irqfd:
        kvm_arch_exit();
out_fail:
        return r;
}
EXPORT_SYMBOL_GPL(kvm_init);

void kvm_exit(void)
{
        int cpu;

        debugfs_remove_recursive(kvm_debugfs_dir);
        misc_deregister(&kvm_dev);
        for_each_possible_cpu(cpu)
                free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
        kmem_cache_destroy(kvm_vcpu_cache);
        kvm_async_pf_deinit();
        unregister_syscore_ops(&kvm_syscore_ops);
        unregister_reboot_notifier(&kvm_reboot_notifier);
        cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
        on_each_cpu(hardware_disable_nolock, NULL, 1);
        kvm_arch_hardware_unsetup();
        kvm_arch_exit();
        kvm_irqfd_exit();
        free_cpumask_var(cpus_hardware_enabled);
        kvm_vfio_ops_exit();
}
EXPORT_SYMBOL_GPL(kvm_exit);

struct kvm_vm_worker_thread_context {
        struct kvm *kvm;
        struct task_struct *parent;
        struct completion init_done;
        kvm_vm_thread_fn_t thread_fn;
        uintptr_t data;
        int err;
};

static int kvm_vm_worker_thread(void *context)
{
        /*
         * The init_context is allocated on the stack of the parent thread, so
         * we have to locally copy anything that is needed beyond initialization
         */
        struct kvm_vm_worker_thread_context *init_context = context;
        struct task_struct *parent;
        struct kvm *kvm = init_context->kvm;
        kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
        uintptr_t data = init_context->data;
        int err;

        err = kthread_park(current);
        /* kthread_park(current) is never supposed to return an error */
        WARN_ON(err != 0);
        if (err)
                goto init_complete;

        err = cgroup_attach_task_all(init_context->parent, current);
        if (err) {
                kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
                        __func__, err);
                goto init_complete;
        }

        set_user_nice(current, task_nice(init_context->parent));

init_complete:
        init_context->err = err;
        complete(&init_context->init_done);
        init_context = NULL;

        if (err)
                goto out;

        /* Wait to be woken up by the spawner before proceeding. */
        kthread_parkme();

        if (!kthread_should_stop())
                err = thread_fn(kvm, data);

out:
        /*
         * Move kthread back to its original cgroup to prevent it lingering in
         * the cgroup of the VM process, after the latter finishes its
         * execution.
         *
         * kthread_stop() waits on the 'exited' completion condition which is
         * set in exit_mm(), via mm_release(), in do_exit(). However, the
         * kthread is removed from the cgroup in the cgroup_exit() which is
         * called after the exit_mm(). This causes the kthread_stop() to return
         * before the kthread actually quits the cgroup.
         */
        rcu_read_lock();
        parent = rcu_dereference(current->real_parent);
        get_task_struct(parent);
        rcu_read_unlock();
        cgroup_attach_task_all(parent, current);
        put_task_struct(parent);

        return err;
}

int kvm_vm_create_worker_thread(struct kvm *kvm, kvm_vm_thread_fn_t thread_fn,
                                uintptr_t data, const char *name,
                                struct task_struct **thread_ptr)
{
        struct kvm_vm_worker_thread_context init_context = {};
        struct task_struct *thread;

        *thread_ptr = NULL;
        init_context.kvm = kvm;
        init_context.parent = current;
        init_context.thread_fn = thread_fn;
        init_context.data = data;
        init_completion(&init_context.init_done);

        thread = kthread_run(kvm_vm_worker_thread, &init_context,
                             "%s-%d", name, task_pid_nr(current));
        if (IS_ERR(thread))
                return PTR_ERR(thread);

        /* kthread_run is never supposed to return NULL */
        WARN_ON(thread == NULL);

        wait_for_completion(&init_context.init_done);

        if (!init_context.err)
                *thread_ptr = thread;

        return init_context.err;
}