[sfrench/cifs-2.6.git] / arch / arm64 / kernel / fpsimd.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * FP/SIMD context switching and fault handling
 *
 * Copyright (C) 2012 ARM Ltd.
 * Author: Catalin Marinas <catalin.marinas@arm.com>
 */

#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/bottom_half.h>
#include <linux/bug.h>
#include <linux/cache.h>
#include <linux/compat.h>
#include <linux/compiler.h>
#include <linux/cpu.h>
#include <linux/cpu_pm.h>
#include <linux/ctype.h>
#include <linux/kernel.h>
#include <linux/linkage.h>
#include <linux/irqflags.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/prctl.h>
#include <linux/preempt.h>
#include <linux/ptrace.h>
#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/stddef.h>
#include <linux/sysctl.h>
#include <linux/swab.h>

#include <asm/esr.h>
#include <asm/exception.h>
#include <asm/fpsimd.h>
#include <asm/cpufeature.h>
#include <asm/cputype.h>
#include <asm/neon.h>
#include <asm/processor.h>
#include <asm/simd.h>
#include <asm/sigcontext.h>
#include <asm/sysreg.h>
#include <asm/traps.h>
#include <asm/virt.h>

#define FPEXC_IOF       (1 << 0)
#define FPEXC_DZF       (1 << 1)
#define FPEXC_OFF       (1 << 2)
#define FPEXC_UFF       (1 << 3)
#define FPEXC_IXF       (1 << 4)
#define FPEXC_IDF       (1 << 7)

/*
 * (Note: in this discussion, statements about FPSIMD apply equally to SVE.)
 *
 * In order to reduce the number of times the FPSIMD state is needlessly saved
 * and restored, we need to keep track of two things:
 * (a) for each task, we need to remember which CPU was the last one to have
 *     the task's FPSIMD state loaded into its FPSIMD registers;
 * (b) for each CPU, we need to remember which task's userland FPSIMD state has
 *     been loaded into its FPSIMD registers most recently, or whether it has
 *     been used to perform kernel mode NEON in the meantime.
 *
 * For (a), we add a fpsimd_cpu field to thread_struct, which gets updated to
 * the id of the current CPU every time the state is loaded onto a CPU. For (b),
 * we add the per-cpu variable 'fpsimd_last_state' (below), which contains the
 * address of the userland FPSIMD state of the task that was loaded onto the CPU
 * the most recently, or NULL if kernel mode NEON has been performed after that.
 *
 * With this in place, we no longer have to restore the next FPSIMD state right
 * when switching between tasks. Instead, we can defer this check to userland
 * resume, at which time we verify whether the CPU's fpsimd_last_state and the
 * task's fpsimd_cpu are still mutually in sync. If this is the case, we
 * can omit the FPSIMD restore.
 *
 * As an optimization, we use the thread_info flag TIF_FOREIGN_FPSTATE to
 * indicate whether or not the userland FPSIMD state of the current task is
 * present in the registers. The flag is set unless the FPSIMD registers of this
 * CPU currently contain the most recent userland FPSIMD state of the current
 * task. If the task is behaving as a VMM, then this is will be managed by
 * KVM which will clear it to indicate that the vcpu FPSIMD state is currently
 * loaded on the CPU, allowing the state to be saved if a FPSIMD-aware
 * softirq kicks in. Upon vcpu_put(), KVM will save the vcpu FP state and
 * flag the register state as invalid.
 *
 * In order to allow softirq handlers to use FPSIMD, kernel_neon_begin() may
 * save the task's FPSIMD context back to task_struct from softirq context.
 * To prevent this from racing with the manipulation of the task's FPSIMD state
 * from task context and thereby corrupting the state, it is necessary to
 * protect any manipulation of a task's fpsimd_state or TIF_FOREIGN_FPSTATE
 * flag with {, __}get_cpu_fpsimd_context(). This will still allow softirqs to
 * run but prevent them to use FPSIMD.
 *
 * For a certain task, the sequence may look something like this:
 * - the task gets scheduled in; if both the task's fpsimd_cpu field
 *   contains the id of the current CPU, and the CPU's fpsimd_last_state per-cpu
 *   variable points to the task's fpsimd_state, the TIF_FOREIGN_FPSTATE flag is
 *   cleared, otherwise it is set;
 *
 * - the task returns to userland; if TIF_FOREIGN_FPSTATE is set, the task's
 *   userland FPSIMD state is copied from memory to the registers, the task's
 *   fpsimd_cpu field is set to the id of the current CPU, the current
 *   CPU's fpsimd_last_state pointer is set to this task's fpsimd_state and the
 *   TIF_FOREIGN_FPSTATE flag is cleared;
 *
 * - the task executes an ordinary syscall; upon return to userland, the
 *   TIF_FOREIGN_FPSTATE flag will still be cleared, so no FPSIMD state is
 *   restored;
 *
 * - the task executes a syscall which executes some NEON instructions; this is
 *   preceded by a call to kernel_neon_begin(), which copies the task's FPSIMD
 *   register contents to memory, clears the fpsimd_last_state per-cpu variable
 *   and sets the TIF_FOREIGN_FPSTATE flag;
 *
 * - the task gets preempted after kernel_neon_end() is called; as we have not
 *   returned from the 2nd syscall yet, TIF_FOREIGN_FPSTATE is still set so
 *   whatever is in the FPSIMD registers is not saved to memory, but discarded.
 */
struct fpsimd_last_state_struct {
        struct user_fpsimd_state *st;
        void *sve_state;
        void *za_state;
        u64 *svcr;
        unsigned int sve_vl;
        unsigned int sme_vl;
        enum fp_type *fp_type;
        enum fp_type to_save;
};

static DEFINE_PER_CPU(struct fpsimd_last_state_struct, fpsimd_last_state);

__ro_after_init struct vl_info vl_info[ARM64_VEC_MAX] = {
#ifdef CONFIG_ARM64_SVE
        [ARM64_VEC_SVE] = {
                .type                   = ARM64_VEC_SVE,
                .name                   = "SVE",
                .min_vl                 = SVE_VL_MIN,
                .max_vl                 = SVE_VL_MIN,
                .max_virtualisable_vl   = SVE_VL_MIN,
        },
#endif
#ifdef CONFIG_ARM64_SME
        [ARM64_VEC_SME] = {
                .type                   = ARM64_VEC_SME,
                .name                   = "SME",
        },
#endif
};

static unsigned int vec_vl_inherit_flag(enum vec_type type)
{
        switch (type) {
        case ARM64_VEC_SVE:
                return TIF_SVE_VL_INHERIT;
        case ARM64_VEC_SME:
                return TIF_SME_VL_INHERIT;
        default:
                WARN_ON_ONCE(1);
                return 0;
        }
}

struct vl_config {
        int __default_vl;               /* Default VL for tasks */
};

static struct vl_config vl_config[ARM64_VEC_MAX];

static inline int get_default_vl(enum vec_type type)
{
        return READ_ONCE(vl_config[type].__default_vl);
}

#ifdef CONFIG_ARM64_SVE

static inline int get_sve_default_vl(void)
{
        return get_default_vl(ARM64_VEC_SVE);
}

static inline void set_default_vl(enum vec_type type, int val)
{
        WRITE_ONCE(vl_config[type].__default_vl, val);
}

static inline void set_sve_default_vl(int val)
{
        set_default_vl(ARM64_VEC_SVE, val);
}

static void __percpu *efi_sve_state;

#else /* ! CONFIG_ARM64_SVE */

/* Dummy declaration for code that will be optimised out: */
extern void __percpu *efi_sve_state;

#endif /* ! CONFIG_ARM64_SVE */

#ifdef CONFIG_ARM64_SME

static int get_sme_default_vl(void)
{
        return get_default_vl(ARM64_VEC_SME);
}

static void set_sme_default_vl(int val)
{
        set_default_vl(ARM64_VEC_SME, val);
}

static void sme_free(struct task_struct *);

#else

static inline void sme_free(struct task_struct *t) { }

#endif

DEFINE_PER_CPU(bool, fpsimd_context_busy);
EXPORT_PER_CPU_SYMBOL(fpsimd_context_busy);

static void fpsimd_bind_task_to_cpu(void);

static void __get_cpu_fpsimd_context(void)
{
        bool busy = __this_cpu_xchg(fpsimd_context_busy, true);

        WARN_ON(busy);
}

/*
 * Claim ownership of the CPU FPSIMD context for use by the calling context.
 *
 * The caller may freely manipulate the FPSIMD context metadata until
 * put_cpu_fpsimd_context() is called.
 *
 * The double-underscore version must only be called if you know the task
 * can't be preempted.
 *
 * On RT kernels local_bh_disable() is not sufficient because it only
 * serializes soft interrupt related sections via a local lock, but stays
 * preemptible. Disabling preemption is the right choice here as bottom
 * half processing is always in thread context on RT kernels so it
 * implicitly prevents bottom half processing as well.
 */
static void get_cpu_fpsimd_context(void)
{
        if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                local_bh_disable();
        else
                preempt_disable();
        __get_cpu_fpsimd_context();
}

static void __put_cpu_fpsimd_context(void)
{
        bool busy = __this_cpu_xchg(fpsimd_context_busy, false);

        WARN_ON(!busy); /* No matching get_cpu_fpsimd_context()? */
}

/*
 * Release the CPU FPSIMD context.
 *
 * Must be called from a context in which get_cpu_fpsimd_context() was
 * previously called, with no call to put_cpu_fpsimd_context() in the
 * meantime.
 */
static void put_cpu_fpsimd_context(void)
{
        __put_cpu_fpsimd_context();
        if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                local_bh_enable();
        else
                preempt_enable();
}

static bool have_cpu_fpsimd_context(void)
{
        return !preemptible() && __this_cpu_read(fpsimd_context_busy);
}

unsigned int task_get_vl(const struct task_struct *task, enum vec_type type)
{
        return task->thread.vl[type];
}

void task_set_vl(struct task_struct *task, enum vec_type type,
                 unsigned long vl)
{
        task->thread.vl[type] = vl;
}

unsigned int task_get_vl_onexec(const struct task_struct *task,
                                enum vec_type type)
{
        return task->thread.vl_onexec[type];
}

void task_set_vl_onexec(struct task_struct *task, enum vec_type type,
                        unsigned long vl)
{
        task->thread.vl_onexec[type] = vl;
}

/*
 * TIF_SME controls whether a task can use SME without trapping while
 * in userspace, when TIF_SME is set then we must have storage
 * alocated in sve_state and za_state to store the contents of both ZA
 * and the SVE registers for both streaming and non-streaming modes.
 *
 * If both SVCR.ZA and SVCR.SM are disabled then at any point we
 * may disable TIF_SME and reenable traps.
 */


/*
 * TIF_SVE controls whether a task can use SVE without trapping while
 * in userspace, and also (together with TIF_SME) the way a task's
 * FPSIMD/SVE state is stored in thread_struct.
 *
 * The kernel uses this flag to track whether a user task is actively
 * using SVE, and therefore whether full SVE register state needs to
 * be tracked.  If not, the cheaper FPSIMD context handling code can
 * be used instead of the more costly SVE equivalents.
 *
 *  * TIF_SVE or SVCR.SM set:
 *
 *    The task can execute SVE instructions while in userspace without
 *    trapping to the kernel.
 *
 *    During any syscall, the kernel may optionally clear TIF_SVE and
 *    discard the vector state except for the FPSIMD subset.
 *
 *  * TIF_SVE clear:
 *
 *    An attempt by the user task to execute an SVE instruction causes
 *    do_sve_acc() to be called, which does some preparation and then
 *    sets TIF_SVE.
 *
 * During any syscall, the kernel may optionally clear TIF_SVE and
 * discard the vector state except for the FPSIMD subset.
 *
 * The data will be stored in one of two formats:
 *
 *  * FPSIMD only - FP_STATE_FPSIMD:
 *
 *    When the FPSIMD only state stored task->thread.fp_type is set to
 *    FP_STATE_FPSIMD, the FPSIMD registers V0-V31 are encoded in
 *    task->thread.uw.fpsimd_state; bits [max : 128] for each of Z0-Z31 are
 *    logically zero but not stored anywhere; P0-P15 and FFR are not
 *    stored and have unspecified values from userspace's point of
 *    view.  For hygiene purposes, the kernel zeroes them on next use,
 *    but userspace is discouraged from relying on this.
 *
 *    task->thread.sve_state does not need to be non-NULL, valid or any
 *    particular size: it must not be dereferenced and any data stored
 *    there should be considered stale and not referenced.
 *
 *  * SVE state - FP_STATE_SVE:
 *
 *    When the full SVE state is stored task->thread.fp_type is set to
 *    FP_STATE_SVE and Z0-Z31 (incorporating Vn in bits[127:0] or the
 *    corresponding Zn), P0-P15 and FFR are encoded in in
 *    task->thread.sve_state, formatted appropriately for vector
 *    length task->thread.sve_vl or, if SVCR.SM is set,
 *    task->thread.sme_vl. The storage for the vector registers in
 *    task->thread.uw.fpsimd_state should be ignored.
 *
 *    task->thread.sve_state must point to a valid buffer at least
 *    sve_state_size(task) bytes in size. The data stored in
 *    task->thread.uw.fpsimd_state.vregs should be considered stale
 *    and not referenced.
 *
 *  * FPSR and FPCR are always stored in task->thread.uw.fpsimd_state
 *    irrespective of whether TIF_SVE is clear or set, since these are
 *    not vector length dependent.
 */

/*
 * Update current's FPSIMD/SVE registers from thread_struct.
 *
 * This function should be called only when the FPSIMD/SVE state in
 * thread_struct is known to be up to date, when preparing to enter
 * userspace.
 */
static void task_fpsimd_load(void)
{
        bool restore_sve_regs = false;
        bool restore_ffr;

        WARN_ON(!system_supports_fpsimd());
        WARN_ON(!have_cpu_fpsimd_context());

        if (system_supports_sve()) {
                switch (current->thread.fp_type) {
                case FP_STATE_FPSIMD:
                        /* Stop tracking SVE for this task until next use. */
                        if (test_and_clear_thread_flag(TIF_SVE))
                                sve_user_disable();
                        break;
                case FP_STATE_SVE:
                        if (!thread_sm_enabled(&current->thread) &&
                            !WARN_ON_ONCE(!test_and_set_thread_flag(TIF_SVE)))
                                sve_user_enable();

                        if (test_thread_flag(TIF_SVE))
                                sve_set_vq(sve_vq_from_vl(task_get_sve_vl(current)) - 1);

                        restore_sve_regs = true;
                        restore_ffr = true;
                        break;
                default:
                        /*
                         * This indicates either a bug in
                         * fpsimd_save() or memory corruption, we
                         * should always record an explicit format
                         * when we save. We always at least have the
                         * memory allocated for FPSMID registers so
                         * try that and hope for the best.
                         */
                        WARN_ON_ONCE(1);
                        clear_thread_flag(TIF_SVE);
                        break;
                }
        }

        /* Restore SME, override SVE register configuration if needed */
        if (system_supports_sme()) {
                unsigned long sme_vl = task_get_sme_vl(current);

                /* Ensure VL is set up for restoring data */
                if (test_thread_flag(TIF_SME))
                        sme_set_vq(sve_vq_from_vl(sme_vl) - 1);

                write_sysreg_s(current->thread.svcr, SYS_SVCR);

                if (thread_za_enabled(&current->thread))
                        za_load_state(current->thread.za_state);

                if (thread_sm_enabled(&current->thread))
                        restore_ffr = system_supports_fa64();
        }

        if (restore_sve_regs) {
                WARN_ON_ONCE(current->thread.fp_type != FP_STATE_SVE);
                sve_load_state(sve_pffr(&current->thread),
                               &current->thread.uw.fpsimd_state.fpsr,
                               restore_ffr);
        } else {
                WARN_ON_ONCE(current->thread.fp_type != FP_STATE_FPSIMD);
                fpsimd_load_state(&current->thread.uw.fpsimd_state);
        }
}

/*
 * Ensure FPSIMD/SVE storage in memory for the loaded context is up to
 * date with respect to the CPU registers. Note carefully that the
 * current context is the context last bound to the CPU stored in
 * last, if KVM is involved this may be the guest VM context rather
 * than the host thread for the VM pointed to by current. This means
 * that we must always reference the state storage via last rather
 * than via current, if we are saving KVM state then it will have
 * ensured that the type of registers to save is set in last->to_save.
 */
static void fpsimd_save(void)
{
        struct fpsimd_last_state_struct const *last =
                this_cpu_ptr(&fpsimd_last_state);
        /* set by fpsimd_bind_task_to_cpu() or fpsimd_bind_state_to_cpu() */
        bool save_sve_regs = false;
        bool save_ffr;
        unsigned int vl;

        WARN_ON(!system_supports_fpsimd());
        WARN_ON(!have_cpu_fpsimd_context());

        if (test_thread_flag(TIF_FOREIGN_FPSTATE))
                return;

        /*
         * If a task is in a syscall the ABI allows us to only
         * preserve the state shared with FPSIMD so don't bother
         * saving the full SVE state in that case.
         */
        if ((last->to_save == FP_STATE_CURRENT && test_thread_flag(TIF_SVE) &&
             !in_syscall(current_pt_regs())) ||
            last->to_save == FP_STATE_SVE) {
                save_sve_regs = true;
                save_ffr = true;
                vl = last->sve_vl;
        }

        if (system_supports_sme()) {
                u64 *svcr = last->svcr;

                *svcr = read_sysreg_s(SYS_SVCR);

                if (*svcr & SVCR_ZA_MASK)
                        za_save_state(last->za_state);

                /* If we are in streaming mode override regular SVE. */
                if (*svcr & SVCR_SM_MASK) {
                        save_sve_regs = true;
                        save_ffr = system_supports_fa64();
                        vl = last->sme_vl;
                }
        }

        if (IS_ENABLED(CONFIG_ARM64_SVE) && save_sve_regs) {
                /* Get the configured VL from RDVL, will account for SM */
                if (WARN_ON(sve_get_vl() != vl)) {
                        /*
                         * Can't save the user regs, so current would
                         * re-enter user with corrupt state.
                         * There's no way to recover, so kill it:
                         */
                        force_signal_inject(SIGKILL, SI_KERNEL, 0, 0);
                        return;
                }

                sve_save_state((char *)last->sve_state +
                                        sve_ffr_offset(vl),
                               &last->st->fpsr, save_ffr);
                *last->fp_type = FP_STATE_SVE;
        } else {
                fpsimd_save_state(last->st);
                *last->fp_type = FP_STATE_FPSIMD;
        }
}

/*
 * All vector length selection from userspace comes through here.
 * We're on a slow path, so some sanity-checks are included.
 * If things go wrong there's a bug somewhere, but try to fall back to a
 * safe choice.
 */
static unsigned int find_supported_vector_length(enum vec_type type,
                                                 unsigned int vl)
{
        struct vl_info *info = &vl_info[type];
        int bit;
        int max_vl = info->max_vl;

        if (WARN_ON(!sve_vl_valid(vl)))
                vl = info->min_vl;

        if (WARN_ON(!sve_vl_valid(max_vl)))
                max_vl = info->min_vl;

        if (vl > max_vl)
                vl = max_vl;
        if (vl < info->min_vl)
                vl = info->min_vl;

        bit = find_next_bit(info->vq_map, SVE_VQ_MAX,
                            __vq_to_bit(sve_vq_from_vl(vl)));
        return sve_vl_from_vq(__bit_to_vq(bit));
}

#if defined(CONFIG_ARM64_SVE) && defined(CONFIG_SYSCTL)

static int vec_proc_do_default_vl(struct ctl_table *table, int write,
                                  void *buffer, size_t *lenp, loff_t *ppos)
{
        struct vl_info *info = table->extra1;
        enum vec_type type = info->type;
        int ret;
        int vl = get_default_vl(type);
        struct ctl_table tmp_table = {
                .data = &vl,
                .maxlen = sizeof(vl),
        };

        ret = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
        if (ret || !write)
                return ret;

        /* Writing -1 has the special meaning "set to max": */
        if (vl == -1)
                vl = info->max_vl;

        if (!sve_vl_valid(vl))
                return -EINVAL;

        set_default_vl(type, find_supported_vector_length(type, vl));
        return 0;
}

static struct ctl_table sve_default_vl_table[] = {
        {
                .procname       = "sve_default_vector_length",
                .mode           = 0644,
                .proc_handler   = vec_proc_do_default_vl,
                .extra1         = &vl_info[ARM64_VEC_SVE],
        },
        { }
};

static int __init sve_sysctl_init(void)
{
        if (system_supports_sve())
                if (!register_sysctl("abi", sve_default_vl_table))
                        return -EINVAL;

        return 0;
}

#else /* ! (CONFIG_ARM64_SVE && CONFIG_SYSCTL) */
static int __init sve_sysctl_init(void) { return 0; }
#endif /* ! (CONFIG_ARM64_SVE && CONFIG_SYSCTL) */

#if defined(CONFIG_ARM64_SME) && defined(CONFIG_SYSCTL)
static struct ctl_table sme_default_vl_table[] = {
        {
                .procname       = "sme_default_vector_length",
                .mode           = 0644,
                .proc_handler   = vec_proc_do_default_vl,
                .extra1         = &vl_info[ARM64_VEC_SME],
        },
        { }
};

static int __init sme_sysctl_init(void)
{
        if (system_supports_sme())
                if (!register_sysctl("abi", sme_default_vl_table))
                        return -EINVAL;

        return 0;
}

#else /* ! (CONFIG_ARM64_SME && CONFIG_SYSCTL) */
static int __init sme_sysctl_init(void) { return 0; }
#endif /* ! (CONFIG_ARM64_SME && CONFIG_SYSCTL) */

#define ZREG(sve_state, vq, n) ((char *)(sve_state) +           \
        (SVE_SIG_ZREG_OFFSET(vq, n) - SVE_SIG_REGS_OFFSET))

#ifdef CONFIG_CPU_BIG_ENDIAN
static __uint128_t arm64_cpu_to_le128(__uint128_t x)
{
        u64 a = swab64(x);
        u64 b = swab64(x >> 64);

        return ((__uint128_t)a << 64) | b;
}
#else
static __uint128_t arm64_cpu_to_le128(__uint128_t x)
{
        return x;
}
#endif

#define arm64_le128_to_cpu(x) arm64_cpu_to_le128(x)

static void __fpsimd_to_sve(void *sst, struct user_fpsimd_state const *fst,
                            unsigned int vq)
{
        unsigned int i;
        __uint128_t *p;

        for (i = 0; i < SVE_NUM_ZREGS; ++i) {
                p = (__uint128_t *)ZREG(sst, vq, i);
                *p = arm64_cpu_to_le128(fst->vregs[i]);
        }
}

/*
 * Transfer the FPSIMD state in task->thread.uw.fpsimd_state to
 * task->thread.sve_state.
 *
 * Task can be a non-runnable task, or current.  In the latter case,
 * the caller must have ownership of the cpu FPSIMD context before calling
 * this function.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 * task->thread.uw.fpsimd_state must be up to date before calling this
 * function.
 */
static void fpsimd_to_sve(struct task_struct *task)
{
        unsigned int vq;
        void *sst = task->thread.sve_state;
        struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state;

        if (!system_supports_sve())
                return;

        vq = sve_vq_from_vl(thread_get_cur_vl(&task->thread));
        __fpsimd_to_sve(sst, fst, vq);
}

/*
 * Transfer the SVE state in task->thread.sve_state to
 * task->thread.uw.fpsimd_state.
 *
 * Task can be a non-runnable task, or current.  In the latter case,
 * the caller must have ownership of the cpu FPSIMD context before calling
 * this function.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 * task->thread.sve_state must be up to date before calling this function.
 */
static void sve_to_fpsimd(struct task_struct *task)
{
        unsigned int vq, vl;
        void const *sst = task->thread.sve_state;
        struct user_fpsimd_state *fst = &task->thread.uw.fpsimd_state;
        unsigned int i;
        __uint128_t const *p;

        if (!system_supports_sve())
                return;

        vl = thread_get_cur_vl(&task->thread);
        vq = sve_vq_from_vl(vl);
        for (i = 0; i < SVE_NUM_ZREGS; ++i) {
                p = (__uint128_t const *)ZREG(sst, vq, i);
                fst->vregs[i] = arm64_le128_to_cpu(*p);
        }
}

#ifdef CONFIG_ARM64_SVE
/*
 * Call __sve_free() directly only if you know task can't be scheduled
 * or preempted.
 */
static void __sve_free(struct task_struct *task)
{
        kfree(task->thread.sve_state);
        task->thread.sve_state = NULL;
}

static void sve_free(struct task_struct *task)
{
        WARN_ON(test_tsk_thread_flag(task, TIF_SVE));

        __sve_free(task);
}

/*
 * Return how many bytes of memory are required to store the full SVE
 * state for task, given task's currently configured vector length.
 */
size_t sve_state_size(struct task_struct const *task)
{
        unsigned int vl = 0;

        if (system_supports_sve())
                vl = task_get_sve_vl(task);
        if (system_supports_sme())
                vl = max(vl, task_get_sme_vl(task));

        return SVE_SIG_REGS_SIZE(sve_vq_from_vl(vl));
}

/*
 * Ensure that task->thread.sve_state is allocated and sufficiently large.
 *
 * This function should be used only in preparation for replacing
 * task->thread.sve_state with new data.  The memory is always zeroed
 * here to prevent stale data from showing through: this is done in
 * the interest of testability and predictability: except in the
 * do_sve_acc() case, there is no ABI requirement to hide stale data
 * written previously be task.
 */
void sve_alloc(struct task_struct *task, bool flush)
{
        if (task->thread.sve_state) {
                if (flush)
                        memset(task->thread.sve_state, 0,
                               sve_state_size(task));
                return;
        }

        /* This is a small allocation (maximum ~8KB) and Should Not Fail. */
        task->thread.sve_state =
                kzalloc(sve_state_size(task), GFP_KERNEL);
}


/*
 * Force the FPSIMD state shared with SVE to be updated in the SVE state
 * even if the SVE state is the current active state.
 *
 * This should only be called by ptrace.  task must be non-runnable.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 */
void fpsimd_force_sync_to_sve(struct task_struct *task)
{
        fpsimd_to_sve(task);
}

/*
 * Ensure that task->thread.sve_state is up to date with respect to
 * the user task, irrespective of when SVE is in use or not.
 *
 * This should only be called by ptrace.  task must be non-runnable.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 */
void fpsimd_sync_to_sve(struct task_struct *task)
{
        if (!test_tsk_thread_flag(task, TIF_SVE) &&
            !thread_sm_enabled(&task->thread))
                fpsimd_to_sve(task);
}

/*
 * Ensure that task->thread.uw.fpsimd_state is up to date with respect to
 * the user task, irrespective of whether SVE is in use or not.
 *
 * This should only be called by ptrace.  task must be non-runnable.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 */
void sve_sync_to_fpsimd(struct task_struct *task)
{
        if (task->thread.fp_type == FP_STATE_SVE)
                sve_to_fpsimd(task);
}

/*
 * Ensure that task->thread.sve_state is up to date with respect to
 * the task->thread.uw.fpsimd_state.
 *
 * This should only be called by ptrace to merge new FPSIMD register
 * values into a task for which SVE is currently active.
 * task must be non-runnable.
 * task->thread.sve_state must point to at least sve_state_size(task)
 * bytes of allocated kernel memory.
 * task->thread.uw.fpsimd_state must already have been initialised with
 * the new FPSIMD register values to be merged in.
 */
void sve_sync_from_fpsimd_zeropad(struct task_struct *task)
{
        unsigned int vq;
        void *sst = task->thread.sve_state;
        struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state;

        if (!test_tsk_thread_flag(task, TIF_SVE))
                return;

        vq = sve_vq_from_vl(thread_get_cur_vl(&task->thread));

        memset(sst, 0, SVE_SIG_REGS_SIZE(vq));
        __fpsimd_to_sve(sst, fst, vq);
}

int vec_set_vector_length(struct task_struct *task, enum vec_type type,
                          unsigned long vl, unsigned long flags)
{
        if (flags & ~(unsigned long)(PR_SVE_VL_INHERIT |
                                     PR_SVE_SET_VL_ONEXEC))
                return -EINVAL;

        if (!sve_vl_valid(vl))
                return -EINVAL;

        /*
         * Clamp to the maximum vector length that VL-agnostic code
         * can work with.  A flag may be assigned in the future to
         * allow setting of larger vector lengths without confusing
         * older software.
         */
        if (vl > VL_ARCH_MAX)
                vl = VL_ARCH_MAX;

        vl = find_supported_vector_length(type, vl);

        if (flags & (PR_SVE_VL_INHERIT |
                     PR_SVE_SET_VL_ONEXEC))
                task_set_vl_onexec(task, type, vl);
        else
                /* Reset VL to system default on next exec: */
                task_set_vl_onexec(task, type, 0);

        /* Only actually set the VL if not deferred: */
        if (flags & PR_SVE_SET_VL_ONEXEC)
                goto out;

        if (vl == task_get_vl(task, type))
                goto out;

        /*
         * To ensure the FPSIMD bits of the SVE vector registers are preserved,
         * write any live register state back to task_struct, and convert to a
         * regular FPSIMD thread.
         */
        if (task == current) {
                get_cpu_fpsimd_context();

                fpsimd_save();
        }

        fpsimd_flush_task_state(task);
        if (test_and_clear_tsk_thread_flag(task, TIF_SVE) ||
            thread_sm_enabled(&task->thread)) {
                sve_to_fpsimd(task);
                task->thread.fp_type = FP_STATE_FPSIMD;
        }

        if (system_supports_sme() && type == ARM64_VEC_SME) {
                task->thread.svcr &= ~(SVCR_SM_MASK |
                                       SVCR_ZA_MASK);
                clear_thread_flag(TIF_SME);
        }

        if (task == current)
                put_cpu_fpsimd_context();

        /*
         * Force reallocation of task SVE and SME state to the correct
         * size on next use:
         */
        sve_free(task);
        if (system_supports_sme() && type == ARM64_VEC_SME)
                sme_free(task);

        task_set_vl(task, type, vl);

out:
        update_tsk_thread_flag(task, vec_vl_inherit_flag(type),
                               flags & PR_SVE_VL_INHERIT);

        return 0;
}

/*
 * Encode the current vector length and flags for return.
 * This is only required for prctl(): ptrace has separate fields.
 * SVE and SME use the same bits for _ONEXEC and _INHERIT.
 *
 * flags are as for vec_set_vector_length().
 */
static int vec_prctl_status(enum vec_type type, unsigned long flags)
{
        int ret;

        if (flags & PR_SVE_SET_VL_ONEXEC)
                ret = task_get_vl_onexec(current, type);
        else
                ret = task_get_vl(current, type);

        if (test_thread_flag(vec_vl_inherit_flag(type)))
                ret |= PR_SVE_VL_INHERIT;

        return ret;
}

/* PR_SVE_SET_VL */
int sve_set_current_vl(unsigned long arg)
{
        unsigned long vl, flags;
        int ret;

        vl = arg & PR_SVE_VL_LEN_MASK;
        flags = arg & ~vl;

        if (!system_supports_sve() || is_compat_task())
                return -EINVAL;

        ret = vec_set_vector_length(current, ARM64_VEC_SVE, vl, flags);
        if (ret)
                return ret;

        return vec_prctl_status(ARM64_VEC_SVE, flags);
}

/* PR_SVE_GET_VL */
int sve_get_current_vl(void)
{
        if (!system_supports_sve() || is_compat_task())
                return -EINVAL;

        return vec_prctl_status(ARM64_VEC_SVE, 0);
}

#ifdef CONFIG_ARM64_SME
/* PR_SME_SET_VL */
int sme_set_current_vl(unsigned long arg)
{
        unsigned long vl, flags;
        int ret;

        vl = arg & PR_SME_VL_LEN_MASK;
        flags = arg & ~vl;

        if (!system_supports_sme() || is_compat_task())
                return -EINVAL;

        ret = vec_set_vector_length(current, ARM64_VEC_SME, vl, flags);
        if (ret)
                return ret;

        return vec_prctl_status(ARM64_VEC_SME, flags);
}

/* PR_SME_GET_VL */
int sme_get_current_vl(void)
{
        if (!system_supports_sme() || is_compat_task())
                return -EINVAL;

        return vec_prctl_status(ARM64_VEC_SME, 0);
}
#endif /* CONFIG_ARM64_SME */

static void vec_probe_vqs(struct vl_info *info,
                          DECLARE_BITMAP(map, SVE_VQ_MAX))
{
        unsigned int vq, vl;

        bitmap_zero(map, SVE_VQ_MAX);

        for (vq = SVE_VQ_MAX; vq >= SVE_VQ_MIN; --vq) {
                write_vl(info->type, vq - 1); /* self-syncing */

                switch (info->type) {
                case ARM64_VEC_SVE:
                        vl = sve_get_vl();
                        break;
                case ARM64_VEC_SME:
                        vl = sme_get_vl();
                        break;
                default:
                        vl = 0;
                        break;
                }

                /* Minimum VL identified? */
                if (sve_vq_from_vl(vl) > vq)
                        break;

                vq = sve_vq_from_vl(vl); /* skip intervening lengths */
                set_bit(__vq_to_bit(vq), map);
        }
}

/*
 * Initialise the set of known supported VQs for the boot CPU.
 * This is called during kernel boot, before secondary CPUs are brought up.
 */
void __init vec_init_vq_map(enum vec_type type)
{
        struct vl_info *info = &vl_info[type];
        vec_probe_vqs(info, info->vq_map);
        bitmap_copy(info->vq_partial_map, info->vq_map, SVE_VQ_MAX);
}

/*
 * If we haven't committed to the set of supported VQs yet, filter out
 * those not supported by the current CPU.
 * This function is called during the bring-up of early secondary CPUs only.
 */
void vec_update_vq_map(enum vec_type type)
{
        struct vl_info *info = &vl_info[type];
        DECLARE_BITMAP(tmp_map, SVE_VQ_MAX);

        vec_probe_vqs(info, tmp_map);
        bitmap_and(info->vq_map, info->vq_map, tmp_map, SVE_VQ_MAX);
        bitmap_or(info->vq_partial_map, info->vq_partial_map, tmp_map,
                  SVE_VQ_MAX);
}

/*
 * Check whether the current CPU supports all VQs in the committed set.
 * This function is called during the bring-up of late secondary CPUs only.
 */
int vec_verify_vq_map(enum vec_type type)
{
        struct vl_info *info = &vl_info[type];
        DECLARE_BITMAP(tmp_map, SVE_VQ_MAX);
        unsigned long b;

        vec_probe_vqs(info, tmp_map);

        bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX);
        if (bitmap_intersects(tmp_map, info->vq_map, SVE_VQ_MAX)) {
                pr_warn("%s: cpu%d: Required vector length(s) missing\n",
                        info->name, smp_processor_id());
                return -EINVAL;
        }

        if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available())
                return 0;

        /*
         * For KVM, it is necessary to ensure that this CPU doesn't
         * support any vector length that guests may have probed as
         * unsupported.
         */

        /* Recover the set of supported VQs: */
        bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX);
        /* Find VQs supported that are not globally supported: */
        bitmap_andnot(tmp_map, tmp_map, info->vq_map, SVE_VQ_MAX);

        /* Find the lowest such VQ, if any: */
        b = find_last_bit(tmp_map, SVE_VQ_MAX);
        if (b >= SVE_VQ_MAX)
                return 0; /* no mismatches */

        /*
         * Mismatches above sve_max_virtualisable_vl are fine, since
         * no guest is allowed to configure ZCR_EL2.LEN to exceed this:
         */
        if (sve_vl_from_vq(__bit_to_vq(b)) <= info->max_virtualisable_vl) {
                pr_warn("%s: cpu%d: Unsupported vector length(s) present\n",
                        info->name, smp_processor_id());
                return -EINVAL;
        }

        return 0;
}

static void __init sve_efi_setup(void)
{
        int max_vl = 0;
        int i;

        if (!IS_ENABLED(CONFIG_EFI))
                return;

        for (i = 0; i < ARRAY_SIZE(vl_info); i++)
                max_vl = max(vl_info[i].max_vl, max_vl);

        /*
         * alloc_percpu() warns and prints a backtrace if this goes wrong.
         * This is evidence of a crippled system and we are returning void,
         * so no attempt is made to handle this situation here.
         */
        if (!sve_vl_valid(max_vl))
                goto fail;

        efi_sve_state = __alloc_percpu(
                SVE_SIG_REGS_SIZE(sve_vq_from_vl(max_vl)), SVE_VQ_BYTES);
        if (!efi_sve_state)
                goto fail;

        return;

fail:
        panic("Cannot allocate percpu memory for EFI SVE save/restore");
}

/*
 * Enable SVE for EL1.
 * Intended for use by the cpufeatures code during CPU boot.
 */
void sve_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
{
        write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_ZEN_EL1EN, CPACR_EL1);
        isb();
}

/*
 * Read the pseudo-ZCR used by cpufeatures to identify the supported SVE
 * vector length.
 *
 * Use only if SVE is present.
 * This function clobbers the SVE vector length.
 */
u64 read_zcr_features(void)
{
        u64 zcr;
        unsigned int vq_max;

        /*
         * Set the maximum possible VL, and write zeroes to all other
         * bits to see if they stick.
         */
        sve_kernel_enable(NULL);
        write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL1);

        zcr = read_sysreg_s(SYS_ZCR_EL1);
        zcr &= ~(u64)ZCR_ELx_LEN_MASK; /* find sticky 1s outside LEN field */
        vq_max = sve_vq_from_vl(sve_get_vl());
        zcr |= vq_max - 1; /* set LEN field to maximum effective value */

        return zcr;
}

void __init sve_setup(void)
{
        struct vl_info *info = &vl_info[ARM64_VEC_SVE];
        u64 zcr;
        DECLARE_BITMAP(tmp_map, SVE_VQ_MAX);
        unsigned long b;

        if (!system_supports_sve())
                return;

        /*
         * The SVE architecture mandates support for 128-bit vectors,
         * so sve_vq_map must have at least SVE_VQ_MIN set.
         * If something went wrong, at least try to patch it up:
         */
        if (WARN_ON(!test_bit(__vq_to_bit(SVE_VQ_MIN), info->vq_map)))
                set_bit(__vq_to_bit(SVE_VQ_MIN), info->vq_map);

        zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1);
        info->max_vl = sve_vl_from_vq((zcr & ZCR_ELx_LEN_MASK) + 1);

        /*
         * Sanity-check that the max VL we determined through CPU features
         * corresponds properly to sve_vq_map.  If not, do our best:
         */
        if (WARN_ON(info->max_vl != find_supported_vector_length(ARM64_VEC_SVE,
                                                                 info->max_vl)))
                info->max_vl = find_supported_vector_length(ARM64_VEC_SVE,
                                                            info->max_vl);

        /*
         * For the default VL, pick the maximum supported value <= 64.
         * VL == 64 is guaranteed not to grow the signal frame.
         */
        set_sve_default_vl(find_supported_vector_length(ARM64_VEC_SVE, 64));

        bitmap_andnot(tmp_map, info->vq_partial_map, info->vq_map,
                      SVE_VQ_MAX);

        b = find_last_bit(tmp_map, SVE_VQ_MAX);
        if (b >= SVE_VQ_MAX)
                /* No non-virtualisable VLs found */
                info->max_virtualisable_vl = SVE_VQ_MAX;
        else if (WARN_ON(b == SVE_VQ_MAX - 1))
                /* No virtualisable VLs?  This is architecturally forbidden. */
                info->max_virtualisable_vl = SVE_VQ_MIN;
        else /* b + 1 < SVE_VQ_MAX */
                info->max_virtualisable_vl = sve_vl_from_vq(__bit_to_vq(b + 1));

        if (info->max_virtualisable_vl > info->max_vl)
                info->max_virtualisable_vl = info->max_vl;

        pr_info("%s: maximum available vector length %u bytes per vector\n",
                info->name, info->max_vl);
        pr_info("%s: default vector length %u bytes per vector\n",
                info->name, get_sve_default_vl());

        /* KVM decides whether to support mismatched systems. Just warn here: */
        if (sve_max_virtualisable_vl() < sve_max_vl())
                pr_warn("%s: unvirtualisable vector lengths present\n",
                        info->name);

        sve_efi_setup();
}

/*
 * Called from the put_task_struct() path, which cannot get here
 * unless dead_task is really dead and not schedulable.
 */
void fpsimd_release_task(struct task_struct *dead_task)
{
        __sve_free(dead_task);
        sme_free(dead_task);
}

#endif /* CONFIG_ARM64_SVE */

#ifdef CONFIG_ARM64_SME

/*
 * Ensure that task->thread.za_state is allocated and sufficiently large.
 *
 * This function should be used only in preparation for replacing
 * task->thread.za_state with new data.  The memory is always zeroed
 * here to prevent stale data from showing through: this is done in
 * the interest of testability and predictability, the architecture
 * guarantees that when ZA is enabled it will be zeroed.
 */
void sme_alloc(struct task_struct *task)
{
        if (task->thread.za_state) {
                memset(task->thread.za_state, 0, za_state_size(task));
                return;
        }

        /* This could potentially be up to 64K. */
        task->thread.za_state =
                kzalloc(za_state_size(task), GFP_KERNEL);
}

static void sme_free(struct task_struct *task)
{
        kfree(task->thread.za_state);
        task->thread.za_state = NULL;
}

void sme_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
{
        /* Set priority for all PEs to architecturally defined minimum */
        write_sysreg_s(read_sysreg_s(SYS_SMPRI_EL1) & ~SMPRI_EL1_PRIORITY_MASK,
                       SYS_SMPRI_EL1);

        /* Allow SME in kernel */
        write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_SMEN_EL1EN, CPACR_EL1);
        isb();

        /* Allow EL0 to access TPIDR2 */
        write_sysreg(read_sysreg(SCTLR_EL1) | SCTLR_ELx_ENTP2, SCTLR_EL1);
        isb();
}

/*
 * This must be called after sme_kernel_enable(), we rely on the
 * feature table being sorted to ensure this.
 */
void fa64_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
{
        /* Allow use of FA64 */
        write_sysreg_s(read_sysreg_s(SYS_SMCR_EL1) | SMCR_ELx_FA64_MASK,
                       SYS_SMCR_EL1);
}

/*
 * Read the pseudo-SMCR used by cpufeatures to identify the supported
 * vector length.
 *
 * Use only if SME is present.
 * This function clobbers the SME vector length.
 */
u64 read_smcr_features(void)
{
        u64 smcr;
        unsigned int vq_max;

        sme_kernel_enable(NULL);
        sme_smstart_sm();

        /*
         * Set the maximum possible VL.
         */
        write_sysreg_s(read_sysreg_s(SYS_SMCR_EL1) | SMCR_ELx_LEN_MASK,
                       SYS_SMCR_EL1);

        smcr = read_sysreg_s(SYS_SMCR_EL1);
        smcr &= ~(u64)SMCR_ELx_LEN_MASK; /* Only the LEN field */
        vq_max = sve_vq_from_vl(sve_get_vl());
        smcr |= vq_max - 1; /* set LEN field to maximum effective value */

        sme_smstop_sm();

        return smcr;
}

void __init sme_setup(void)
{
        struct vl_info *info = &vl_info[ARM64_VEC_SME];
        u64 smcr;
        int min_bit;

        if (!system_supports_sme())
                return;

        /*
         * SME doesn't require any particular vector length be
         * supported but it does require at least one.  We should have
         * disabled the feature entirely while bringing up CPUs but
         * let's double check here.
         */
        WARN_ON(bitmap_empty(info->vq_map, SVE_VQ_MAX));

        min_bit = find_last_bit(info->vq_map, SVE_VQ_MAX);
        info->min_vl = sve_vl_from_vq(__bit_to_vq(min_bit));

        smcr = read_sanitised_ftr_reg(SYS_SMCR_EL1);
        info->max_vl = sve_vl_from_vq((smcr & SMCR_ELx_LEN_MASK) + 1);

        /*
         * Sanity-check that the max VL we determined through CPU features
         * corresponds properly to sme_vq_map.  If not, do our best:
         */
        if (WARN_ON(info->max_vl != find_supported_vector_length(ARM64_VEC_SME,
                                                                 info->max_vl)))
                info->max_vl = find_supported_vector_length(ARM64_VEC_SME,
                                                            info->max_vl);

        WARN_ON(info->min_vl > info->max_vl);

        /*
         * For the default VL, pick the maximum supported value <= 32
         * (256 bits) if there is one since this is guaranteed not to
         * grow the signal frame when in streaming mode, otherwise the
         * minimum available VL will be used.
         */
        set_sme_default_vl(find_supported_vector_length(ARM64_VEC_SME, 32));

        pr_info("SME: minimum available vector length %u bytes per vector\n",
                info->min_vl);
        pr_info("SME: maximum available vector length %u bytes per vector\n",
                info->max_vl);
        pr_info("SME: default vector length %u bytes per vector\n",
                get_sme_default_vl());
}

#endif /* CONFIG_ARM64_SME */

static void sve_init_regs(void)
{
        /*
         * Convert the FPSIMD state to SVE, zeroing all the state that
         * is not shared with FPSIMD. If (as is likely) the current
         * state is live in the registers then do this there and
         * update our metadata for the current task including
         * disabling the trap, otherwise update our in-memory copy.
         * We are guaranteed to not be in streaming mode, we can only
         * take a SVE trap when not in streaming mode and we can't be
         * in streaming mode when taking a SME trap.
         */
        if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
                unsigned long vq_minus_one =
                        sve_vq_from_vl(task_get_sve_vl(current)) - 1;
                sve_set_vq(vq_minus_one);
                sve_flush_live(true, vq_minus_one);
                fpsimd_bind_task_to_cpu();
        } else {
                fpsimd_to_sve(current);
                current->thread.fp_type = FP_STATE_SVE;
        }
}

/*
 * Trapped SVE access
 *
 * Storage is allocated for the full SVE state, the current FPSIMD
 * register contents are migrated across, and the access trap is
 * disabled.
 *
 * TIF_SVE should be clear on entry: otherwise, fpsimd_restore_current_state()
 * would have disabled the SVE access trap for userspace during
 * ret_to_user, making an SVE access trap impossible in that case.
 */
void do_sve_acc(unsigned long esr, struct pt_regs *regs)
{
        /* Even if we chose not to use SVE, the hardware could still trap: */
        if (unlikely(!system_supports_sve()) || WARN_ON(is_compat_task())) {
                force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
                return;
        }

        sve_alloc(current, true);
        if (!current->thread.sve_state) {
                force_sig(SIGKILL);
                return;
        }

        get_cpu_fpsimd_context();

        if (test_and_set_thread_flag(TIF_SVE))
                WARN_ON(1); /* SVE access shouldn't have trapped */

        /*
         * Even if the task can have used streaming mode we can only
         * generate SVE access traps in normal SVE mode and
         * transitioning out of streaming mode may discard any
         * streaming mode state.  Always clear the high bits to avoid
         * any potential errors tracking what is properly initialised.
         */
        sve_init_regs();

        put_cpu_fpsimd_context();
}

/*
 * Trapped SME access
 *
 * Storage is allocated for the full SVE and SME state, the current
 * FPSIMD register contents are migrated to SVE if SVE is not already
 * active, and the access trap is disabled.
 *
 * TIF_SME should be clear on entry: otherwise, fpsimd_restore_current_state()
 * would have disabled the SME access trap for userspace during
 * ret_to_user, making an SVE access trap impossible in that case.
 */
void do_sme_acc(unsigned long esr, struct pt_regs *regs)
{
        /* Even if we chose not to use SME, the hardware could still trap: */
        if (unlikely(!system_supports_sme()) || WARN_ON(is_compat_task())) {
                force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
                return;
        }

        /*
         * If this not a trap due to SME being disabled then something
         * is being used in the wrong mode, report as SIGILL.
         */
        if (ESR_ELx_ISS(esr) != ESR_ELx_SME_ISS_SME_DISABLED) {
                force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
                return;
        }

        sve_alloc(current, false);
        sme_alloc(current);
        if (!current->thread.sve_state || !current->thread.za_state) {
                force_sig(SIGKILL);
                return;
        }

        get_cpu_fpsimd_context();

        /* With TIF_SME userspace shouldn't generate any traps */
        if (test_and_set_thread_flag(TIF_SME))
                WARN_ON(1);

        if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
                unsigned long vq_minus_one =
                        sve_vq_from_vl(task_get_sme_vl(current)) - 1;
                sme_set_vq(vq_minus_one);

                fpsimd_bind_task_to_cpu();
        }

        put_cpu_fpsimd_context();
}

/*
 * Trapped FP/ASIMD access.
 */
void do_fpsimd_acc(unsigned long esr, struct pt_regs *regs)
{
        /* TODO: implement lazy context saving/restoring */
        WARN_ON(1);
}

/*
 * Raise a SIGFPE for the current process.
 */
void do_fpsimd_exc(unsigned long esr, struct pt_regs *regs)
{
        unsigned int si_code = FPE_FLTUNK;

        if (esr & ESR_ELx_FP_EXC_TFV) {
                if (esr & FPEXC_IOF)
                        si_code = FPE_FLTINV;
                else if (esr & FPEXC_DZF)
                        si_code = FPE_FLTDIV;
                else if (esr & FPEXC_OFF)
                        si_code = FPE_FLTOVF;
                else if (esr & FPEXC_UFF)
                        si_code = FPE_FLTUND;
                else if (esr & FPEXC_IXF)
                        si_code = FPE_FLTRES;
        }

        send_sig_fault(SIGFPE, si_code,
                       (void __user *)instruction_pointer(regs),
                       current);
}

void fpsimd_thread_switch(struct task_struct *next)
{
        bool wrong_task, wrong_cpu;

        if (!system_supports_fpsimd())
                return;

        __get_cpu_fpsimd_context();

        /* Save unsaved fpsimd state, if any: */
        fpsimd_save();

        /*
         * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's
         * state.  For kernel threads, FPSIMD registers are never loaded
         * and wrong_task and wrong_cpu will always be true.
         */
        wrong_task = __this_cpu_read(fpsimd_last_state.st) !=
                                        &next->thread.uw.fpsimd_state;
        wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id();

        update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE,
                               wrong_task || wrong_cpu);

        __put_cpu_fpsimd_context();
}

static void fpsimd_flush_thread_vl(enum vec_type type)
{
        int vl, supported_vl;

        /*
         * Reset the task vector length as required.  This is where we
         * ensure that all user tasks have a valid vector length
         * configured: no kernel task can become a user task without
         * an exec and hence a call to this function.  By the time the
         * first call to this function is made, all early hardware
         * probing is complete, so __sve_default_vl should be valid.
         * If a bug causes this to go wrong, we make some noise and
         * try to fudge thread.sve_vl to a safe value here.
         */
        vl = task_get_vl_onexec(current, type);
        if (!vl)
                vl = get_default_vl(type);

        if (WARN_ON(!sve_vl_valid(vl)))
                vl = vl_info[type].min_vl;

        supported_vl = find_supported_vector_length(type, vl);
        if (WARN_ON(supported_vl != vl))
                vl = supported_vl;

        task_set_vl(current, type, vl);

        /*
         * If the task is not set to inherit, ensure that the vector
         * length will be reset by a subsequent exec:
         */
        if (!test_thread_flag(vec_vl_inherit_flag(type)))
                task_set_vl_onexec(current, type, 0);
}

void fpsimd_flush_thread(void)
{
        void *sve_state = NULL;
        void *za_state = NULL;

        if (!system_supports_fpsimd())
                return;

        get_cpu_fpsimd_context();

        fpsimd_flush_task_state(current);
        memset(&current->thread.uw.fpsimd_state, 0,
               sizeof(current->thread.uw.fpsimd_state));

        if (system_supports_sve()) {
                clear_thread_flag(TIF_SVE);

                /* Defer kfree() while in atomic context */
                sve_state = current->thread.sve_state;
                current->thread.sve_state = NULL;

                fpsimd_flush_thread_vl(ARM64_VEC_SVE);
        }

        if (system_supports_sme()) {
                clear_thread_flag(TIF_SME);

                /* Defer kfree() while in atomic context */
                za_state = current->thread.za_state;
                current->thread.za_state = NULL;

                fpsimd_flush_thread_vl(ARM64_VEC_SME);
                current->thread.svcr = 0;
        }

        current->thread.fp_type = FP_STATE_FPSIMD;

        put_cpu_fpsimd_context();
        kfree(sve_state);
        kfree(za_state);
}

/*
 * Save the userland FPSIMD state of 'current' to memory, but only if the state
 * currently held in the registers does in fact belong to 'current'
 */
void fpsimd_preserve_current_state(void)
{
        if (!system_supports_fpsimd())
                return;

        get_cpu_fpsimd_context();
        fpsimd_save();
        put_cpu_fpsimd_context();
}

/*
 * Like fpsimd_preserve_current_state(), but ensure that
 * current->thread.uw.fpsimd_state is updated so that it can be copied to
 * the signal frame.
 */
void fpsimd_signal_preserve_current_state(void)
{
        fpsimd_preserve_current_state();
        if (test_thread_flag(TIF_SVE))
                sve_to_fpsimd(current);
}

/*
 * Called by KVM when entering the guest.
 */
void fpsimd_kvm_prepare(void)
{
        if (!system_supports_sve())
                return;

        /*
         * KVM does not save host SVE state since we can only enter
         * the guest from a syscall so the ABI means that only the
         * non-saved SVE state needs to be saved.  If we have left
         * SVE enabled for performance reasons then update the task
         * state to be FPSIMD only.
         */
        get_cpu_fpsimd_context();

        if (test_and_clear_thread_flag(TIF_SVE)) {
                sve_to_fpsimd(current);
                current->thread.fp_type = FP_STATE_FPSIMD;
        }

        put_cpu_fpsimd_context();
}

/*
 * Associate current's FPSIMD context with this cpu
 * The caller must have ownership of the cpu FPSIMD context before calling
 * this function.
 */
static void fpsimd_bind_task_to_cpu(void)
{
        struct fpsimd_last_state_struct *last =
                this_cpu_ptr(&fpsimd_last_state);

        WARN_ON(!system_supports_fpsimd());
        last->st = &current->thread.uw.fpsimd_state;
        last->sve_state = current->thread.sve_state;
        last->za_state = current->thread.za_state;
        last->sve_vl = task_get_sve_vl(current);
        last->sme_vl = task_get_sme_vl(current);
        last->svcr = &current->thread.svcr;
        last->fp_type = &current->thread.fp_type;
        last->to_save = FP_STATE_CURRENT;
        current->thread.fpsimd_cpu = smp_processor_id();

        /*
         * Toggle SVE and SME trapping for userspace if needed, these
         * are serialsied by ret_to_user().
         */
        if (system_supports_sme()) {
                if (test_thread_flag(TIF_SME))
                        sme_user_enable();
                else
                        sme_user_disable();
        }

        if (system_supports_sve()) {
                if (test_thread_flag(TIF_SVE))
                        sve_user_enable();
                else
                        sve_user_disable();
        }
}

void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *st, void *sve_state,
                              unsigned int sve_vl, void *za_state,
                              unsigned int sme_vl, u64 *svcr,
                              enum fp_type *type, enum fp_type to_save)
{
        struct fpsimd_last_state_struct *last =
                this_cpu_ptr(&fpsimd_last_state);

        WARN_ON(!system_supports_fpsimd());
        WARN_ON(!in_softirq() && !irqs_disabled());

        last->st = st;
        last->svcr = svcr;
        last->sve_state = sve_state;
        last->za_state = za_state;
        last->sve_vl = sve_vl;
        last->sme_vl = sme_vl;
        last->fp_type = type;
        last->to_save = to_save;
}

/*
 * Load the userland FPSIMD state of 'current' from memory, but only if the
 * FPSIMD state already held in the registers is /not/ the most recent FPSIMD
 * state of 'current'.  This is called when we are preparing to return to
 * userspace to ensure that userspace sees a good register state.
 */
void fpsimd_restore_current_state(void)
{
        /*
         * For the tasks that were created before we detected the absence of
         * FP/SIMD, the TIF_FOREIGN_FPSTATE could be set via fpsimd_thread_switch(),
         * e.g, init. This could be then inherited by the children processes.
         * If we later detect that the system doesn't support FP/SIMD,
         * we must clear the flag for  all the tasks to indicate that the
         * FPSTATE is clean (as we can't have one) to avoid looping for ever in
         * do_notify_resume().
         */
        if (!system_supports_fpsimd()) {
                clear_thread_flag(TIF_FOREIGN_FPSTATE);
                return;
        }

        get_cpu_fpsimd_context();

        if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
                task_fpsimd_load();
                fpsimd_bind_task_to_cpu();
        }

        put_cpu_fpsimd_context();
}

/*
 * Load an updated userland FPSIMD state for 'current' from memory and set the
 * flag that indicates that the FPSIMD register contents are the most recent
 * FPSIMD state of 'current'. This is used by the signal code to restore the
 * register state when returning from a signal handler in FPSIMD only cases,
 * any SVE context will be discarded.
 */
void fpsimd_update_current_state(struct user_fpsimd_state const *state)
{
        if (WARN_ON(!system_supports_fpsimd()))
                return;

        get_cpu_fpsimd_context();

        current->thread.uw.fpsimd_state = *state;
        if (test_thread_flag(TIF_SVE))
                fpsimd_to_sve(current);

        task_fpsimd_load();
        fpsimd_bind_task_to_cpu();

        clear_thread_flag(TIF_FOREIGN_FPSTATE);

        put_cpu_fpsimd_context();
}

/*
 * Invalidate live CPU copies of task t's FPSIMD state
 *
 * This function may be called with preemption enabled.  The barrier()
 * ensures that the assignment to fpsimd_cpu is visible to any
 * preemption/softirq that could race with set_tsk_thread_flag(), so
 * that TIF_FOREIGN_FPSTATE cannot be spuriously re-cleared.
 *
 * The final barrier ensures that TIF_FOREIGN_FPSTATE is seen set by any
 * subsequent code.
 */
void fpsimd_flush_task_state(struct task_struct *t)
{
        t->thread.fpsimd_cpu = NR_CPUS;
        /*
         * If we don't support fpsimd, bail out after we have
         * reset the fpsimd_cpu for this task and clear the
         * FPSTATE.
         */
        if (!system_supports_fpsimd())
                return;
        barrier();
        set_tsk_thread_flag(t, TIF_FOREIGN_FPSTATE);

        barrier();
}

/*
 * Invalidate any task's FPSIMD state that is present on this cpu.
 * The FPSIMD context should be acquired with get_cpu_fpsimd_context()
 * before calling this function.
 */
static void fpsimd_flush_cpu_state(void)
{
        WARN_ON(!system_supports_fpsimd());
        __this_cpu_write(fpsimd_last_state.st, NULL);

        /*
         * Leaving streaming mode enabled will cause issues for any kernel
         * NEON and leaving streaming mode or ZA enabled may increase power
         * consumption.
         */
        if (system_supports_sme())
                sme_smstop();

        set_thread_flag(TIF_FOREIGN_FPSTATE);
}

/*
 * Save the FPSIMD state to memory and invalidate cpu view.
 * This function must be called with preemption disabled.
 */
void fpsimd_save_and_flush_cpu_state(void)
{
        if (!system_supports_fpsimd())
                return;
        WARN_ON(preemptible());
        __get_cpu_fpsimd_context();
        fpsimd_save();
        fpsimd_flush_cpu_state();
        __put_cpu_fpsimd_context();
}

#ifdef CONFIG_KERNEL_MODE_NEON

/*
 * Kernel-side NEON support functions
 */

/*
 * kernel_neon_begin(): obtain the CPU FPSIMD registers for use by the calling
 * context
 *
 * Must not be called unless may_use_simd() returns true.
 * Task context in the FPSIMD registers is saved back to memory as necessary.
 *
 * A matching call to kernel_neon_end() must be made before returning from the
 * calling context.
 *
 * The caller may freely use the FPSIMD registers until kernel_neon_end() is
 * called.
 */
void kernel_neon_begin(void)
{
        if (WARN_ON(!system_supports_fpsimd()))
                return;

        BUG_ON(!may_use_simd());

        get_cpu_fpsimd_context();

        /* Save unsaved fpsimd state, if any: */
        fpsimd_save();

        /* Invalidate any task state remaining in the fpsimd regs: */
        fpsimd_flush_cpu_state();
}
EXPORT_SYMBOL(kernel_neon_begin);

/*
 * kernel_neon_end(): give the CPU FPSIMD registers back to the current task
 *
 * Must be called from a context in which kernel_neon_begin() was previously
 * called, with no call to kernel_neon_end() in the meantime.
 *
 * The caller must not use the FPSIMD registers after this function is called,
 * unless kernel_neon_begin() is called again in the meantime.
 */
void kernel_neon_end(void)
{
        if (!system_supports_fpsimd())
                return;

        put_cpu_fpsimd_context();
}
EXPORT_SYMBOL(kernel_neon_end);

#ifdef CONFIG_EFI

static DEFINE_PER_CPU(struct user_fpsimd_state, efi_fpsimd_state);
static DEFINE_PER_CPU(bool, efi_fpsimd_state_used);
static DEFINE_PER_CPU(bool, efi_sve_state_used);
static DEFINE_PER_CPU(bool, efi_sm_state);

/*
 * EFI runtime services support functions
 *
 * The ABI for EFI runtime services allows EFI to use FPSIMD during the call.
 * This means that for EFI (and only for EFI), we have to assume that FPSIMD
 * is always used rather than being an optional accelerator.
 *
 * These functions provide the necessary support for ensuring FPSIMD
 * save/restore in the contexts from which EFI is used.
 *
 * Do not use them for any other purpose -- if tempted to do so, you are
 * either doing something wrong or you need to propose some refactoring.
 */

/*
 * __efi_fpsimd_begin(): prepare FPSIMD for making an EFI runtime services call
 */
void __efi_fpsimd_begin(void)
{
        if (!system_supports_fpsimd())
                return;

        WARN_ON(preemptible());

        if (may_use_simd()) {
                kernel_neon_begin();
        } else {
                /*
                 * If !efi_sve_state, SVE can't be in use yet and doesn't need
                 * preserving:
                 */
                if (system_supports_sve() && likely(efi_sve_state)) {
                        char *sve_state = this_cpu_ptr(efi_sve_state);
                        bool ffr = true;
                        u64 svcr;

                        __this_cpu_write(efi_sve_state_used, true);

                        if (system_supports_sme()) {
                                svcr = read_sysreg_s(SYS_SVCR);

                                __this_cpu_write(efi_sm_state,
                                                 svcr & SVCR_SM_MASK);

                                /*
                                 * Unless we have FA64 FFR does not
                                 * exist in streaming mode.
                                 */
                                if (!system_supports_fa64())
                                        ffr = !(svcr & SVCR_SM_MASK);
                        }

                        sve_save_state(sve_state + sve_ffr_offset(sve_max_vl()),
                                       &this_cpu_ptr(&efi_fpsimd_state)->fpsr,
                                       ffr);

                        if (system_supports_sme())
                                sysreg_clear_set_s(SYS_SVCR,
                                                   SVCR_SM_MASK, 0);

                } else {
                        fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state));
                }

                __this_cpu_write(efi_fpsimd_state_used, true);
        }
}

/*
 * __efi_fpsimd_end(): clean up FPSIMD after an EFI runtime services call
 */
void __efi_fpsimd_end(void)
{
        if (!system_supports_fpsimd())
                return;

        if (!__this_cpu_xchg(efi_fpsimd_state_used, false)) {
                kernel_neon_end();
        } else {
                if (system_supports_sve() &&
                    likely(__this_cpu_read(efi_sve_state_used))) {
                        char const *sve_state = this_cpu_ptr(efi_sve_state);
                        bool ffr = true;

                        /*
                         * Restore streaming mode; EFI calls are
                         * normal function calls so should not return in
                         * streaming mode.
                         */
                        if (system_supports_sme()) {
                                if (__this_cpu_read(efi_sm_state)) {
                                        sysreg_clear_set_s(SYS_SVCR,
                                                           0,
                                                           SVCR_SM_MASK);

                                        /*
                                         * Unless we have FA64 FFR does not
                                         * exist in streaming mode.
                                         */
                                        if (!system_supports_fa64())
                                                ffr = false;
                                }
                        }

                        sve_load_state(sve_state + sve_ffr_offset(sve_max_vl()),
                                       &this_cpu_ptr(&efi_fpsimd_state)->fpsr,
                                       ffr);

                        __this_cpu_write(efi_sve_state_used, false);
                } else {
                        fpsimd_load_state(this_cpu_ptr(&efi_fpsimd_state));
                }
        }
}

#endif /* CONFIG_EFI */

#endif /* CONFIG_KERNEL_MODE_NEON */

#ifdef CONFIG_CPU_PM
static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
                                  unsigned long cmd, void *v)
{
        switch (cmd) {
        case CPU_PM_ENTER:
                fpsimd_save_and_flush_cpu_state();
                break;
        case CPU_PM_EXIT:
                break;
        case CPU_PM_ENTER_FAILED:
        default:
                return NOTIFY_DONE;
        }
        return NOTIFY_OK;
}

static struct notifier_block fpsimd_cpu_pm_notifier_block = {
        .notifier_call = fpsimd_cpu_pm_notifier,
};

static void __init fpsimd_pm_init(void)
{
        cpu_pm_register_notifier(&fpsimd_cpu_pm_notifier_block);
}

#else
static inline void fpsimd_pm_init(void) { }
#endif /* CONFIG_CPU_PM */

#ifdef CONFIG_HOTPLUG_CPU
static int fpsimd_cpu_dead(unsigned int cpu)
{
        per_cpu(fpsimd_last_state.st, cpu) = NULL;
        return 0;
}

static inline void fpsimd_hotplug_init(void)
{
        cpuhp_setup_state_nocalls(CPUHP_ARM64_FPSIMD_DEAD, "arm64/fpsimd:dead",
                                  NULL, fpsimd_cpu_dead);
}

#else
static inline void fpsimd_hotplug_init(void) { }
#endif

/*
 * FP/SIMD support code initialisation.
 */
static int __init fpsimd_init(void)
{
        if (cpu_have_named_feature(FP)) {
                fpsimd_pm_init();
                fpsimd_hotplug_init();
        } else {
                pr_notice("Floating-point is not implemented\n");
        }

        if (!cpu_have_named_feature(ASIMD))
                pr_notice("Advanced SIMD is not implemented\n");


        if (cpu_have_named_feature(SME) && !cpu_have_named_feature(SVE))
                pr_notice("SME is implemented but not SVE\n");

        sve_sysctl_init();
        sme_sysctl_init();

        return 0;
}
core_initcall(fpsimd_init);