virt/kvm/async_pf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * kvm asynchronous fault support
   4  *
   5  * Copyright 2010 Red Hat, Inc.
   6  *
   7  * Author:
   8  *      Gleb Natapov <gleb@redhat.com>
   9  */
  10
  11 #include <linux/kvm_host.h>
  12 #include <linux/slab.h>
  13 #include <linux/module.h>
  14 #include <linux/mmu_context.h>
  15 #include <linux/sched/mm.h>
  16
  17 #include "async_pf.h"
  18 #include <trace/events/kvm.h>
  19
  20 static struct kmem_cache *async_pf_cache;
  21
  22 int kvm_async_pf_init(void)
  23 {
  24         async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
  25
  26         if (!async_pf_cache)
  27                 return -ENOMEM;
  28
  29         return 0;
  30 }
  31
  32 void kvm_async_pf_deinit(void)
  33 {
  34         kmem_cache_destroy(async_pf_cache);
  35         async_pf_cache = NULL;
  36 }
  37
  38 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
  39 {
  40         INIT_LIST_HEAD(&vcpu->async_pf.done);
  41         INIT_LIST_HEAD(&vcpu->async_pf.queue);
  42         spin_lock_init(&vcpu->async_pf.lock);
  43 }
  44
  45 static void async_pf_execute(struct work_struct *work)
  46 {
  47         struct kvm_async_pf *apf =
  48                 container_of(work, struct kvm_async_pf, work);
  49         struct mm_struct *mm = apf->mm;
  50         struct kvm_vcpu *vcpu = apf->vcpu;
  51         unsigned long addr = apf->addr;
  52         gpa_t cr2_or_gpa = apf->cr2_or_gpa;
  53         int locked = 1;
  54         bool first;
  55
  56         might_sleep();
  57
  58         /*
  59          * This work is run asynchronously to the task which owns
  60          * mm and might be done in another context, so we must
  61          * access remotely.
  62          */
  63         mmap_read_lock(mm);
  64         get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, NULL,
  65                         &locked);
  66         if (locked)
  67                 mmap_read_unlock(mm);
  68
  69         if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
  70                 kvm_arch_async_page_present(vcpu, apf);
  71
  72         spin_lock(&vcpu->async_pf.lock);
  73         first = list_empty(&vcpu->async_pf.done);
  74         list_add_tail(&apf->link, &vcpu->async_pf.done);
  75         apf->vcpu = NULL;
  76         spin_unlock(&vcpu->async_pf.lock);
  77
  78         if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
  79                 kvm_arch_async_page_present_queued(vcpu);
  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, cr2_or_gpa);
  87
  88         rcuwait_wake_up(&vcpu->wait);
  89
  90         mmput(mm);
  91         kvm_put_kvm(vcpu->kvm);
  92 }
  93
  94 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
  95 {
  96         spin_lock(&vcpu->async_pf.lock);
  97
  98         /* cancel outstanding work queue item */
  99         while (!list_empty(&vcpu->async_pf.queue)) {
 100                 struct kvm_async_pf *work =
 101                         list_first_entry(&vcpu->async_pf.queue,
 102                                          typeof(*work), queue);
 103                 list_del(&work->queue);
 104
 105                 /*
 106                  * We know it's present in vcpu->async_pf.done, do
 107                  * nothing here.
 108                  */
 109                 if (!work->vcpu)
 110                         continue;
 111
 112                 spin_unlock(&vcpu->async_pf.lock);
 113 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
 114                 flush_work(&work->work);
 115 #else
 116                 if (cancel_work_sync(&work->work)) {
 117                         mmput(work->mm);
 118                         kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
 119                         kmem_cache_free(async_pf_cache, work);
 120                 }
 121 #endif
 122                 spin_lock(&vcpu->async_pf.lock);
 123         }
 124
 125         while (!list_empty(&vcpu->async_pf.done)) {
 126                 struct kvm_async_pf *work =
 127                         list_first_entry(&vcpu->async_pf.done,
 128                                          typeof(*work), link);
 129                 list_del(&work->link);
 130                 kmem_cache_free(async_pf_cache, work);
 131         }
 132         spin_unlock(&vcpu->async_pf.lock);
 133
 134         vcpu->async_pf.queued = 0;
 135 }
 136
 137 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 138 {
 139         struct kvm_async_pf *work;
 140
 141         while (!list_empty_careful(&vcpu->async_pf.done) &&
 142               kvm_arch_can_dequeue_async_page_present(vcpu)) {
 143                 spin_lock(&vcpu->async_pf.lock);
 144                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 145                                               link);
 146                 list_del(&work->link);
 147                 spin_unlock(&vcpu->async_pf.lock);
 148
 149                 kvm_arch_async_page_ready(vcpu, work);
 150                 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
 151                         kvm_arch_async_page_present(vcpu, work);
 152
 153                 list_del(&work->queue);
 154                 vcpu->async_pf.queued--;
 155                 kmem_cache_free(async_pf_cache, work);
 156         }
 157 }
 158
 159 /*
 160  * Try to schedule a job to handle page fault asynchronously. Returns 'true' on
 161  * success, 'false' on failure (page fault has to be handled synchronously).
 162  */
 163 bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 164                         unsigned long hva, struct kvm_arch_async_pf *arch)
 165 {
 166         struct kvm_async_pf *work;
 167
 168         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
 169                 return false;
 170
 171         /* Arch specific code should not do async PF in this case */
 172         if (unlikely(kvm_is_error_hva(hva)))
 173                 return false;
 174
 175         /*
 176          * do alloc nowait since if we are going to sleep anyway we
 177          * may as well sleep faulting in page
 178          */
 179         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
 180         if (!work)
 181                 return false;
 182
 183         work->wakeup_all = false;
 184         work->vcpu = vcpu;
 185         work->cr2_or_gpa = cr2_or_gpa;
 186         work->addr = hva;
 187         work->arch = *arch;
 188         work->mm = current->mm;
 189         mmget(work->mm);
 190         kvm_get_kvm(work->vcpu->kvm);
 191
 192         INIT_WORK(&work->work, async_pf_execute);
 193
 194         list_add_tail(&work->queue, &vcpu->async_pf.queue);
 195         vcpu->async_pf.queued++;
 196         work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);
 197
 198         schedule_work(&work->work);
 199
 200         return true;
 201 }
 202
 203 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 204 {
 205         struct kvm_async_pf *work;
 206         bool first;
 207
 208         if (!list_empty_careful(&vcpu->async_pf.done))
 209                 return 0;
 210
 211         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
 212         if (!work)
 213                 return -ENOMEM;
 214
 215         work->wakeup_all = true;
 216         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 217
 218         spin_lock(&vcpu->async_pf.lock);
 219         first = list_empty(&vcpu->async_pf.done);
 220         list_add_tail(&work->link, &vcpu->async_pf.done);
 221         spin_unlock(&vcpu->async_pf.lock);
 222
 223         if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
 224                 kvm_arch_async_page_present_queued(vcpu);
 225
 226         vcpu->async_pf.queued++;
 227         return 0;
 228 }