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