virt/kvm/async_pf.c

   1 /*
   2  * kvm asynchronous fault support
   3  *
   4  * Copyright 2010 Red Hat, Inc.
   5  *
   6  * Author:
   7  *      Gleb Natapov <gleb@redhat.com>
   8  *
   9  * This file is free software; you can redistribute it and/or modify
  10  * it under the terms of version 2 of the GNU General Public License
  11  * as published by the Free Software Foundation.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software Foundation,
  20  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
  21  */
  22
  23 #include <linux/kvm_host.h>
  24 #include <linux/slab.h>
  25 #include <linux/module.h>
  26 #include <linux/mmu_context.h>
  27
  28 #include "async_pf.h"
  29 #include <trace/events/kvm.h>
  30
  31 static inline void kvm_async_page_present_sync(struct kvm_vcpu *vcpu,
  32                                                struct kvm_async_pf *work)
  33 {
  34 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
  35         kvm_arch_async_page_present(vcpu, work);
  36 #endif
  37 }
  38 static inline void kvm_async_page_present_async(struct kvm_vcpu *vcpu,
  39                                                 struct kvm_async_pf *work)
  40 {
  41 #ifndef CONFIG_KVM_ASYNC_PF_SYNC
  42         kvm_arch_async_page_present(vcpu, work);
  43 #endif
  44 }
  45
  46 static struct kmem_cache *async_pf_cache;
  47
  48 int kvm_async_pf_init(void)
  49 {
  50         async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
  51
  52         if (!async_pf_cache)
  53                 return -ENOMEM;
  54
  55         return 0;
  56 }
  57
  58 void kvm_async_pf_deinit(void)
  59 {
  60         if (async_pf_cache)
  61                 kmem_cache_destroy(async_pf_cache);
  62         async_pf_cache = NULL;
  63 }
  64
  65 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
  66 {
  67         INIT_LIST_HEAD(&vcpu->async_pf.done);
  68         INIT_LIST_HEAD(&vcpu->async_pf.queue);
  69         spin_lock_init(&vcpu->async_pf.lock);
  70 }
  71
  72 static void async_pf_execute(struct work_struct *work)
  73 {
  74         struct kvm_async_pf *apf =
  75                 container_of(work, struct kvm_async_pf, work);
  76         struct mm_struct *mm = apf->mm;
  77         struct kvm_vcpu *vcpu = apf->vcpu;
  78         unsigned long addr = apf->addr;
  79         gva_t gva = apf->gva;
  80
  81         might_sleep();
  82
  83         down_read(&mm->mmap_sem);
  84         get_user_pages(NULL, mm, addr, 1, 1, 0, NULL, NULL);
  85         up_read(&mm->mmap_sem);
  86         kvm_async_page_present_sync(vcpu, apf);
  87
  88         spin_lock(&vcpu->async_pf.lock);
  89         list_add_tail(&apf->link, &vcpu->async_pf.done);
  90         spin_unlock(&vcpu->async_pf.lock);
  91
  92         /*
  93          * apf may be freed by kvm_check_async_pf_completion() after
  94          * this point
  95          */
  96
  97         trace_kvm_async_pf_completed(addr, gva);
  98
  99         if (waitqueue_active(&vcpu->wq))
 100                 wake_up_interruptible(&vcpu->wq);
 101
 102         mmput(mm);
 103         kvm_put_kvm(vcpu->kvm);
 104 }
 105
 106 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
 107 {
 108         /* cancel outstanding work queue item */
 109         while (!list_empty(&vcpu->async_pf.queue)) {
 110                 struct kvm_async_pf *work =
 111                         list_entry(vcpu->async_pf.queue.next,
 112                                    typeof(*work), queue);
 113                 list_del(&work->queue);
 114
 115 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
 116                 flush_work(&work->work);
 117 #else
 118                 if (cancel_work_sync(&work->work)) {
 119                         mmput(work->mm);
 120                         kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
 121                         kmem_cache_free(async_pf_cache, work);
 122                 }
 123 #endif
 124         }
 125
 126         spin_lock(&vcpu->async_pf.lock);
 127         while (!list_empty(&vcpu->async_pf.done)) {
 128                 struct kvm_async_pf *work =
 129                         list_entry(vcpu->async_pf.done.next,
 130                                    typeof(*work), link);
 131                 list_del(&work->link);
 132                 kmem_cache_free(async_pf_cache, work);
 133         }
 134         spin_unlock(&vcpu->async_pf.lock);
 135
 136         vcpu->async_pf.queued = 0;
 137 }
 138
 139 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 140 {
 141         struct kvm_async_pf *work;
 142
 143         while (!list_empty_careful(&vcpu->async_pf.done) &&
 144               kvm_arch_can_inject_async_page_present(vcpu)) {
 145                 spin_lock(&vcpu->async_pf.lock);
 146                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 147                                               link);
 148                 list_del(&work->link);
 149                 spin_unlock(&vcpu->async_pf.lock);
 150
 151                 kvm_arch_async_page_ready(vcpu, work);
 152                 kvm_async_page_present_async(vcpu, work);
 153
 154                 list_del(&work->queue);
 155                 vcpu->async_pf.queued--;
 156                 kmem_cache_free(async_pf_cache, work);
 157         }
 158 }
 159
 160 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
 161                        struct kvm_arch_async_pf *arch)
 162 {
 163         struct kvm_async_pf *work;
 164
 165         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
 166                 return 0;
 167
 168         /* setup delayed work */
 169
 170         /*
 171          * do alloc nowait since if we are going to sleep anyway we
 172          * may as well sleep faulting in page
 173          */
 174         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
 175         if (!work)
 176                 return 0;
 177
 178         work->wakeup_all = false;
 179         work->vcpu = vcpu;
 180         work->gva = gva;
 181         work->addr = hva;
 182         work->arch = *arch;
 183         work->mm = current->mm;
 184         atomic_inc(&work->mm->mm_users);
 185         kvm_get_kvm(work->vcpu->kvm);
 186
 187         /* this can't really happen otherwise gfn_to_pfn_async
 188            would succeed */
 189         if (unlikely(kvm_is_error_hva(work->addr)))
 190                 goto retry_sync;
 191
 192         INIT_WORK(&work->work, async_pf_execute);
 193         if (!schedule_work(&work->work))
 194                 goto retry_sync;
 195
 196         list_add_tail(&work->queue, &vcpu->async_pf.queue);
 197         vcpu->async_pf.queued++;
 198         kvm_arch_async_page_not_present(vcpu, work);
 199         return 1;
 200 retry_sync:
 201         kvm_put_kvm(work->vcpu->kvm);
 202         mmput(work->mm);
 203         kmem_cache_free(async_pf_cache, work);
 204         return 0;
 205 }
 206
 207 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 208 {
 209         struct kvm_async_pf *work;
 210
 211         if (!list_empty_careful(&vcpu->async_pf.done))
 212                 return 0;
 213
 214         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
 215         if (!work)
 216                 return -ENOMEM;
 217
 218         work->wakeup_all = true;
 219         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 220
 221         spin_lock(&vcpu->async_pf.lock);
 222         list_add_tail(&work->link, &vcpu->async_pf.done);
 223         spin_unlock(&vcpu->async_pf.lock);
 224
 225         vcpu->async_pf.queued++;
 226         return 0;
 227 }