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         kmem_cache_destroy(async_pf_cache);
  61         async_pf_cache = NULL;
  62 }
  63
  64 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
  65 {
  66         INIT_LIST_HEAD(&vcpu->async_pf.done);
  67         INIT_LIST_HEAD(&vcpu->async_pf.queue);
  68         spin_lock_init(&vcpu->async_pf.lock);
  69 }
  70
  71 static void async_pf_execute(struct work_struct *work)
  72 {
  73         struct kvm_async_pf *apf =
  74                 container_of(work, struct kvm_async_pf, work);
  75         struct mm_struct *mm = apf->mm;
  76         struct kvm_vcpu *vcpu = apf->vcpu;
  77         unsigned long addr = apf->addr;
  78         gva_t gva = apf->gva;
  79         int locked = 1;
  80
  81         might_sleep();
  82
  83         /*
  84          * This work is run asynchromously to the task which owns
  85          * mm and might be done in another context, so we must
  86          * access remotely.
  87          */
  88         down_read(&mm->mmap_sem);
  89         get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL,
  90                         &locked);
  91         if (locked)
  92                 up_read(&mm->mmap_sem);
  93
  94         kvm_async_page_present_sync(vcpu, apf);
  95
  96         spin_lock(&vcpu->async_pf.lock);
  97         list_add_tail(&apf->link, &vcpu->async_pf.done);
  98         apf->vcpu = NULL;
  99         spin_unlock(&vcpu->async_pf.lock);
 100
 101         /*
 102          * apf may be freed by kvm_check_async_pf_completion() after
 103          * this point
 104          */
 105
 106         trace_kvm_async_pf_completed(addr, gva);
 107
 108         /*
 109          * This memory barrier pairs with prepare_to_wait's set_current_state()
 110          */
 111         smp_mb();
 112         if (swait_active(&vcpu->wq))
 113                 swake_up(&vcpu->wq);
 114
 115         mmput(mm);
 116         kvm_put_kvm(vcpu->kvm);
 117 }
 118
 119 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
 120 {
 121         spin_lock(&vcpu->async_pf.lock);
 122
 123         /* cancel outstanding work queue item */
 124         while (!list_empty(&vcpu->async_pf.queue)) {
 125                 struct kvm_async_pf *work =
 126                         list_first_entry(&vcpu->async_pf.queue,
 127                                          typeof(*work), queue);
 128                 list_del(&work->queue);
 129
 130                 /*
 131                  * We know it's present in vcpu->async_pf.done, do
 132                  * nothing here.
 133                  */
 134                 if (!work->vcpu)
 135                         continue;
 136
 137                 spin_unlock(&vcpu->async_pf.lock);
 138 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
 139                 flush_work(&work->work);
 140 #else
 141                 if (cancel_work_sync(&work->work)) {
 142                         mmput(work->mm);
 143                         kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
 144                         kmem_cache_free(async_pf_cache, work);
 145                 }
 146 #endif
 147                 spin_lock(&vcpu->async_pf.lock);
 148         }
 149
 150         while (!list_empty(&vcpu->async_pf.done)) {
 151                 struct kvm_async_pf *work =
 152                         list_first_entry(&vcpu->async_pf.done,
 153                                          typeof(*work), link);
 154                 list_del(&work->link);
 155                 kmem_cache_free(async_pf_cache, work);
 156         }
 157         spin_unlock(&vcpu->async_pf.lock);
 158
 159         vcpu->async_pf.queued = 0;
 160 }
 161
 162 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 163 {
 164         struct kvm_async_pf *work;
 165
 166         while (!list_empty_careful(&vcpu->async_pf.done) &&
 167               kvm_arch_can_inject_async_page_present(vcpu)) {
 168                 spin_lock(&vcpu->async_pf.lock);
 169                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 170                                               link);
 171                 list_del(&work->link);
 172                 spin_unlock(&vcpu->async_pf.lock);
 173
 174                 kvm_arch_async_page_ready(vcpu, work);
 175                 kvm_async_page_present_async(vcpu, work);
 176
 177                 list_del(&work->queue);
 178                 vcpu->async_pf.queued--;
 179                 kmem_cache_free(async_pf_cache, work);
 180         }
 181 }
 182
 183 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
 184                        struct kvm_arch_async_pf *arch)
 185 {
 186         struct kvm_async_pf *work;
 187
 188         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
 189                 return 0;
 190
 191         /* setup delayed work */
 192
 193         /*
 194          * do alloc nowait since if we are going to sleep anyway we
 195          * may as well sleep faulting in page
 196          */
 197         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
 198         if (!work)
 199                 return 0;
 200
 201         work->wakeup_all = false;
 202         work->vcpu = vcpu;
 203         work->gva = gva;
 204         work->addr = hva;
 205         work->arch = *arch;
 206         work->mm = current->mm;
 207         atomic_inc(&work->mm->mm_users);
 208         kvm_get_kvm(work->vcpu->kvm);
 209
 210         /* this can't really happen otherwise gfn_to_pfn_async
 211            would succeed */
 212         if (unlikely(kvm_is_error_hva(work->addr)))
 213                 goto retry_sync;
 214
 215         INIT_WORK(&work->work, async_pf_execute);
 216         if (!schedule_work(&work->work))
 217                 goto retry_sync;
 218
 219         list_add_tail(&work->queue, &vcpu->async_pf.queue);
 220         vcpu->async_pf.queued++;
 221         kvm_arch_async_page_not_present(vcpu, work);
 222         return 1;
 223 retry_sync:
 224         kvm_put_kvm(work->vcpu->kvm);
 225         mmput(work->mm);
 226         kmem_cache_free(async_pf_cache, work);
 227         return 0;
 228 }
 229
 230 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 231 {
 232         struct kvm_async_pf *work;
 233
 234         if (!list_empty_careful(&vcpu->async_pf.done))
 235                 return 0;
 236
 237         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
 238         if (!work)
 239                 return -ENOMEM;
 240
 241         work->wakeup_all = true;
 242         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 243
 244         spin_lock(&vcpu->async_pf.lock);
 245         list_add_tail(&work->link, &vcpu->async_pf.done);
 246         spin_unlock(&vcpu->async_pf.lock);
 247
 248         vcpu->async_pf.queued++;
 249         return 0;
 250 }