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         get_user_pages_unlocked(NULL, mm, addr, 1, 1, 0, NULL);
  84         kvm_async_page_present_sync(vcpu, apf);
  85
  86         spin_lock(&vcpu->async_pf.lock);
  87         list_add_tail(&apf->link, &vcpu->async_pf.done);
  88         spin_unlock(&vcpu->async_pf.lock);
  89
  90         /*
  91          * apf may be freed by kvm_check_async_pf_completion() after
  92          * this point
  93          */
  94
  95         trace_kvm_async_pf_completed(addr, gva);
  96
  97         /*
  98          * This memory barrier pairs with prepare_to_wait's set_current_state()
  99          */
 100         smp_mb();
 101         if (waitqueue_active(&vcpu->wq))
 102                 wake_up_interruptible(&vcpu->wq);
 103
 104         mmput(mm);
 105         kvm_put_kvm(vcpu->kvm);
 106 }
 107
 108 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
 109 {
 110         /* cancel outstanding work queue item */
 111         while (!list_empty(&vcpu->async_pf.queue)) {
 112                 struct kvm_async_pf *work =
 113                         list_entry(vcpu->async_pf.queue.next,
 114                                    typeof(*work), queue);
 115                 list_del(&work->queue);
 116
 117 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
 118                 flush_work(&work->work);
 119 #else
 120                 if (cancel_work_sync(&work->work)) {
 121                         mmput(work->mm);
 122                         kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
 123                         kmem_cache_free(async_pf_cache, work);
 124                 }
 125 #endif
 126         }
 127
 128         spin_lock(&vcpu->async_pf.lock);
 129         while (!list_empty(&vcpu->async_pf.done)) {
 130                 struct kvm_async_pf *work =
 131                         list_entry(vcpu->async_pf.done.next,
 132                                    typeof(*work), link);
 133                 list_del(&work->link);
 134                 kmem_cache_free(async_pf_cache, work);
 135         }
 136         spin_unlock(&vcpu->async_pf.lock);
 137
 138         vcpu->async_pf.queued = 0;
 139 }
 140
 141 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 142 {
 143         struct kvm_async_pf *work;
 144
 145         while (!list_empty_careful(&vcpu->async_pf.done) &&
 146               kvm_arch_can_inject_async_page_present(vcpu)) {
 147                 spin_lock(&vcpu->async_pf.lock);
 148                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 149                                               link);
 150                 list_del(&work->link);
 151                 spin_unlock(&vcpu->async_pf.lock);
 152
 153                 kvm_arch_async_page_ready(vcpu, work);
 154                 kvm_async_page_present_async(vcpu, work);
 155
 156                 list_del(&work->queue);
 157                 vcpu->async_pf.queued--;
 158                 kmem_cache_free(async_pf_cache, work);
 159         }
 160 }
 161
 162 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
 163                        struct kvm_arch_async_pf *arch)
 164 {
 165         struct kvm_async_pf *work;
 166
 167         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
 168                 return 0;
 169
 170         /* setup delayed work */
 171
 172         /*
 173          * do alloc nowait since if we are going to sleep anyway we
 174          * may as well sleep faulting in page
 175          */
 176         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
 177         if (!work)
 178                 return 0;
 179
 180         work->wakeup_all = false;
 181         work->vcpu = vcpu;
 182         work->gva = gva;
 183         work->addr = hva;
 184         work->arch = *arch;
 185         work->mm = current->mm;
 186         atomic_inc(&work->mm->mm_users);
 187         kvm_get_kvm(work->vcpu->kvm);
 188
 189         /* this can't really happen otherwise gfn_to_pfn_async
 190            would succeed */
 191         if (unlikely(kvm_is_error_hva(work->addr)))
 192                 goto retry_sync;
 193
 194         INIT_WORK(&work->work, async_pf_execute);
 195         if (!schedule_work(&work->work))
 196                 goto retry_sync;
 197
 198         list_add_tail(&work->queue, &vcpu->async_pf.queue);
 199         vcpu->async_pf.queued++;
 200         kvm_arch_async_page_not_present(vcpu, work);
 201         return 1;
 202 retry_sync:
 203         kvm_put_kvm(work->vcpu->kvm);
 204         mmput(work->mm);
 205         kmem_cache_free(async_pf_cache, work);
 206         return 0;
 207 }
 208
 209 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 210 {
 211         struct kvm_async_pf *work;
 212
 213         if (!list_empty_careful(&vcpu->async_pf.done))
 214                 return 0;
 215
 216         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
 217         if (!work)
 218                 return -ENOMEM;
 219
 220         work->wakeup_all = true;
 221         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 222
 223         spin_lock(&vcpu->async_pf.lock);
 224         list_add_tail(&work->link, &vcpu->async_pf.done);
 225         spin_unlock(&vcpu->async_pf.lock);
 226
 227         vcpu->async_pf.queued++;
 228         return 0;
 229 }