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, &locked);
  65         if (locked)
  66                 mmap_read_unlock(mm);
  67
  68         if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
  69                 kvm_arch_async_page_present(vcpu, apf);
  70
  71         spin_lock(&vcpu->async_pf.lock);
  72         first = list_empty(&vcpu->async_pf.done);
  73         list_add_tail(&apf->link, &vcpu->async_pf.done);
  74         apf->vcpu = NULL;
  75         spin_unlock(&vcpu->async_pf.lock);
  76
  77         if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
  78                 kvm_arch_async_page_present_queued(vcpu);
  79
  80         /*
  81          * apf may be freed by kvm_check_async_pf_completion() after
  82          * this point
  83          */
  84
  85         trace_kvm_async_pf_completed(addr, cr2_or_gpa);
  86
  87         __kvm_vcpu_wake_up(vcpu);
  88
  89         mmput(mm);
  90         kvm_put_kvm(vcpu->kvm);
  91 }
  92
  93 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
  94 {
  95         spin_lock(&vcpu->async_pf.lock);
  96
  97         /* cancel outstanding work queue item */
  98         while (!list_empty(&vcpu->async_pf.queue)) {
  99                 struct kvm_async_pf *work =
 100                         list_first_entry(&vcpu->async_pf.queue,
 101                                          typeof(*work), queue);
 102                 list_del(&work->queue);
 103
 104                 /*
 105                  * We know it's present in vcpu->async_pf.done, do
 106                  * nothing here.
 107                  */
 108                 if (!work->vcpu)
 109                         continue;
 110
 111                 spin_unlock(&vcpu->async_pf.lock);
 112 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
 113                 flush_work(&work->work);
 114 #else
 115                 if (cancel_work_sync(&work->work)) {
 116                         mmput(work->mm);
 117                         kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
 118                         kmem_cache_free(async_pf_cache, work);
 119                 }
 120 #endif
 121                 spin_lock(&vcpu->async_pf.lock);
 122         }
 123
 124         while (!list_empty(&vcpu->async_pf.done)) {
 125                 struct kvm_async_pf *work =
 126                         list_first_entry(&vcpu->async_pf.done,
 127                                          typeof(*work), link);
 128                 list_del(&work->link);
 129                 kmem_cache_free(async_pf_cache, work);
 130         }
 131         spin_unlock(&vcpu->async_pf.lock);
 132
 133         vcpu->async_pf.queued = 0;
 134 }
 135
 136 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 137 {
 138         struct kvm_async_pf *work;
 139
 140         while (!list_empty_careful(&vcpu->async_pf.done) &&
 141               kvm_arch_can_dequeue_async_page_present(vcpu)) {
 142                 spin_lock(&vcpu->async_pf.lock);
 143                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 144                                               link);
 145                 list_del(&work->link);
 146                 spin_unlock(&vcpu->async_pf.lock);
 147
 148                 kvm_arch_async_page_ready(vcpu, work);
 149                 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
 150                         kvm_arch_async_page_present(vcpu, work);
 151
 152                 list_del(&work->queue);
 153                 vcpu->async_pf.queued--;
 154                 kmem_cache_free(async_pf_cache, work);
 155         }
 156 }
 157
 158 /*
 159  * Try to schedule a job to handle page fault asynchronously. Returns 'true' on
 160  * success, 'false' on failure (page fault has to be handled synchronously).
 161  */
 162 bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 163                         unsigned long hva, struct kvm_arch_async_pf *arch)
 164 {
 165         struct kvm_async_pf *work;
 166
 167         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
 168                 return false;
 169
 170         /* Arch specific code should not do async PF in this case */
 171         if (unlikely(kvm_is_error_hva(hva)))
 172                 return false;
 173
 174         /*
 175          * do alloc nowait since if we are going to sleep anyway we
 176          * may as well sleep faulting in page
 177          */
 178         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
 179         if (!work)
 180                 return false;
 181
 182         work->wakeup_all = false;
 183         work->vcpu = vcpu;
 184         work->cr2_or_gpa = cr2_or_gpa;
 185         work->addr = hva;
 186         work->arch = *arch;
 187         work->mm = current->mm;
 188         mmget(work->mm);
 189         kvm_get_kvm(work->vcpu->kvm);
 190
 191         INIT_WORK(&work->work, async_pf_execute);
 192
 193         list_add_tail(&work->queue, &vcpu->async_pf.queue);
 194         vcpu->async_pf.queued++;
 195         work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);
 196
 197         schedule_work(&work->work);
 198
 199         return true;
 200 }
 201
 202 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 203 {
 204         struct kvm_async_pf *work;
 205         bool first;
 206
 207         if (!list_empty_careful(&vcpu->async_pf.done))
 208                 return 0;
 209
 210         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
 211         if (!work)
 212                 return -ENOMEM;
 213
 214         work->wakeup_all = true;
 215         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 216
 217         spin_lock(&vcpu->async_pf.lock);
 218         first = list_empty(&vcpu->async_pf.done);
 219         list_add_tail(&work->link, &vcpu->async_pf.done);
 220         spin_unlock(&vcpu->async_pf.lock);
 221
 222         if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
 223                 kvm_arch_async_page_present_queued(vcpu);
 224
 225         vcpu->async_pf.queued++;
 226         return 0;
 227 }