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 struct kmem_cache *async_pf_cache;
  32
  33 int kvm_async_pf_init(void)
  34 {
  35         async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
  36
  37         if (!async_pf_cache)
  38                 return -ENOMEM;
  39
  40         return 0;
  41 }
  42
  43 void kvm_async_pf_deinit(void)
  44 {
  45         if (async_pf_cache)
  46                 kmem_cache_destroy(async_pf_cache);
  47         async_pf_cache = NULL;
  48 }
  49
  50 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
  51 {
  52         INIT_LIST_HEAD(&vcpu->async_pf.done);
  53         INIT_LIST_HEAD(&vcpu->async_pf.queue);
  54         spin_lock_init(&vcpu->async_pf.lock);
  55 }
  56
  57 static void async_pf_execute(struct work_struct *work)
  58 {
  59         struct page *page = NULL;
  60         struct kvm_async_pf *apf =
  61                 container_of(work, struct kvm_async_pf, work);
  62         struct mm_struct *mm = apf->mm;
  63         struct kvm_vcpu *vcpu = apf->vcpu;
  64         unsigned long addr = apf->addr;
  65         gva_t gva = apf->gva;
  66
  67         might_sleep();
  68
  69         use_mm(mm);
  70         down_read(&mm->mmap_sem);
  71         get_user_pages(current, mm, addr, 1, 1, 0, &page, NULL);
  72         up_read(&mm->mmap_sem);
  73         unuse_mm(mm);
  74
  75         spin_lock(&vcpu->async_pf.lock);
  76         list_add_tail(&apf->link, &vcpu->async_pf.done);
  77         apf->page = page;
  78         apf->done = true;
  79         spin_unlock(&vcpu->async_pf.lock);
  80
  81         /*
  82          * apf may be freed by kvm_check_async_pf_completion() after
  83          * this point
  84          */
  85
  86         trace_kvm_async_pf_completed(addr, page, gva);
  87
  88         if (waitqueue_active(&vcpu->wq))
  89                 wake_up_interruptible(&vcpu->wq);
  90
  91         mmdrop(mm);
  92         kvm_put_kvm(vcpu->kvm);
  93 }
  94
  95 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
  96 {
  97         /* cancel outstanding work queue item */
  98         while (!list_empty(&vcpu->async_pf.queue)) {
  99                 struct kvm_async_pf *work =
 100                         list_entry(vcpu->async_pf.queue.next,
 101                                    typeof(*work), queue);
 102                 cancel_work_sync(&work->work);
 103                 list_del(&work->queue);
 104                 if (!work->done) /* work was canceled */
 105                         kmem_cache_free(async_pf_cache, work);
 106         }
 107
 108         spin_lock(&vcpu->async_pf.lock);
 109         while (!list_empty(&vcpu->async_pf.done)) {
 110                 struct kvm_async_pf *work =
 111                         list_entry(vcpu->async_pf.done.next,
 112                                    typeof(*work), link);
 113                 list_del(&work->link);
 114                 if (work->page)
 115                         put_page(work->page);
 116                 kmem_cache_free(async_pf_cache, work);
 117         }
 118         spin_unlock(&vcpu->async_pf.lock);
 119
 120         vcpu->async_pf.queued = 0;
 121 }
 122
 123 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 124 {
 125         struct kvm_async_pf *work;
 126
 127         while (!list_empty_careful(&vcpu->async_pf.done) &&
 128               kvm_arch_can_inject_async_page_present(vcpu)) {
 129                 spin_lock(&vcpu->async_pf.lock);
 130                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 131                                               link);
 132                 list_del(&work->link);
 133                 spin_unlock(&vcpu->async_pf.lock);
 134
 135                 if (work->page)
 136                         kvm_arch_async_page_ready(vcpu, work);
 137                 kvm_arch_async_page_present(vcpu, work);
 138
 139                 list_del(&work->queue);
 140                 vcpu->async_pf.queued--;
 141                 if (work->page)
 142                         put_page(work->page);
 143                 kmem_cache_free(async_pf_cache, work);
 144         }
 145 }
 146
 147 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
 148                        struct kvm_arch_async_pf *arch)
 149 {
 150         struct kvm_async_pf *work;
 151
 152         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
 153                 return 0;
 154
 155         /* setup delayed work */
 156
 157         /*
 158          * do alloc nowait since if we are going to sleep anyway we
 159          * may as well sleep faulting in page
 160          */
 161         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
 162         if (!work)
 163                 return 0;
 164
 165         work->page = NULL;
 166         work->done = false;
 167         work->vcpu = vcpu;
 168         work->gva = gva;
 169         work->addr = gfn_to_hva(vcpu->kvm, gfn);
 170         work->arch = *arch;
 171         work->mm = current->mm;
 172         atomic_inc(&work->mm->mm_count);
 173         kvm_get_kvm(work->vcpu->kvm);
 174
 175         /* this can't really happen otherwise gfn_to_pfn_async
 176            would succeed */
 177         if (unlikely(kvm_is_error_hva(work->addr)))
 178                 goto retry_sync;
 179
 180         INIT_WORK(&work->work, async_pf_execute);
 181         if (!schedule_work(&work->work))
 182                 goto retry_sync;
 183
 184         list_add_tail(&work->queue, &vcpu->async_pf.queue);
 185         vcpu->async_pf.queued++;
 186         kvm_arch_async_page_not_present(vcpu, work);
 187         return 1;
 188 retry_sync:
 189         kvm_put_kvm(work->vcpu->kvm);
 190         mmdrop(work->mm);
 191         kmem_cache_free(async_pf_cache, work);
 192         return 0;
 193 }
 194
 195 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 196 {
 197         struct kvm_async_pf *work;
 198
 199         if (!list_empty_careful(&vcpu->async_pf.done))
 200                 return 0;
 201
 202         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
 203         if (!work)
 204                 return -ENOMEM;
 205
 206         work->page = bad_page;
 207         get_page(bad_page);
 208         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 209
 210         spin_lock(&vcpu->async_pf.lock);
 211         list_add_tail(&work->link, &vcpu->async_pf.done);
 212         spin_unlock(&vcpu->async_pf.lock);
 213
 214         vcpu->async_pf.queued++;
 215         return 0;
 216 }