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