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 inline void kvm_async_page_present_sync(struct kvm_vcpu *vcpu,
  21                                                struct kvm_async_pf *work)
  22 {
  23 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
  24         kvm_arch_async_page_present(vcpu, work);
  25 #endif
  26 }
  27 static inline void kvm_async_page_present_async(struct kvm_vcpu *vcpu,
  28                                                 struct kvm_async_pf *work)
  29 {
  30 #ifndef CONFIG_KVM_ASYNC_PF_SYNC
  31         kvm_arch_async_page_present(vcpu, work);
  32 #endif
  33 }
  34
  35 static struct kmem_cache *async_pf_cache;
  36
  37 int kvm_async_pf_init(void)
  38 {
  39         async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
  40
  41         if (!async_pf_cache)
  42                 return -ENOMEM;
  43
  44         return 0;
  45 }
  46
  47 void kvm_async_pf_deinit(void)
  48 {
  49         kmem_cache_destroy(async_pf_cache);
  50         async_pf_cache = NULL;
  51 }
  52
  53 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
  54 {
  55         INIT_LIST_HEAD(&vcpu->async_pf.done);
  56         INIT_LIST_HEAD(&vcpu->async_pf.queue);
  57         spin_lock_init(&vcpu->async_pf.lock);
  58 }
  59
  60 static void async_pf_execute(struct work_struct *work)
  61 {
  62         struct kvm_async_pf *apf =
  63                 container_of(work, struct kvm_async_pf, work);
  64         struct mm_struct *mm = apf->mm;
  65         struct kvm_vcpu *vcpu = apf->vcpu;
  66         unsigned long addr = apf->addr;
  67         gva_t gva = apf->gva;
  68         int locked = 1;
  69
  70         might_sleep();
  71
  72         /*
  73          * This work is run asynchronously to the task which owns
  74          * mm and might be done in another context, so we must
  75          * access remotely.
  76          */
  77         down_read(&mm->mmap_sem);
  78         get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL,
  79                         &locked);
  80         if (locked)
  81                 up_read(&mm->mmap_sem);
  82
  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         apf->vcpu = NULL;
  88         spin_unlock(&vcpu->async_pf.lock);
  89
  90         /*
  91          * apf may be freed by kvm_check_async_pf_completion() after
  92          * this point
  93          */
  94
  95         trace_kvm_async_pf_completed(addr, gva);
  96
  97         if (swq_has_sleeper(&vcpu->wq))
  98                 swake_up_one(&vcpu->wq);
  99
 100         mmput(mm);
 101         kvm_put_kvm(vcpu->kvm);
 102 }
 103
 104 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
 105 {
 106         spin_lock(&vcpu->async_pf.lock);
 107
 108         /* cancel outstanding work queue item */
 109         while (!list_empty(&vcpu->async_pf.queue)) {
 110                 struct kvm_async_pf *work =
 111                         list_first_entry(&vcpu->async_pf.queue,
 112                                          typeof(*work), queue);
 113                 list_del(&work->queue);
 114
 115                 /*
 116                  * We know it's present in vcpu->async_pf.done, do
 117                  * nothing here.
 118                  */
 119                 if (!work->vcpu)
 120                         continue;
 121
 122                 spin_unlock(&vcpu->async_pf.lock);
 123 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
 124                 flush_work(&work->work);
 125 #else
 126                 if (cancel_work_sync(&work->work)) {
 127                         mmput(work->mm);
 128                         kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
 129                         kmem_cache_free(async_pf_cache, work);
 130                 }
 131 #endif
 132                 spin_lock(&vcpu->async_pf.lock);
 133         }
 134
 135         while (!list_empty(&vcpu->async_pf.done)) {
 136                 struct kvm_async_pf *work =
 137                         list_first_entry(&vcpu->async_pf.done,
 138                                          typeof(*work), link);
 139                 list_del(&work->link);
 140                 kmem_cache_free(async_pf_cache, work);
 141         }
 142         spin_unlock(&vcpu->async_pf.lock);
 143
 144         vcpu->async_pf.queued = 0;
 145 }
 146
 147 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 148 {
 149         struct kvm_async_pf *work;
 150
 151         while (!list_empty_careful(&vcpu->async_pf.done) &&
 152               kvm_arch_can_inject_async_page_present(vcpu)) {
 153                 spin_lock(&vcpu->async_pf.lock);
 154                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 155                                               link);
 156                 list_del(&work->link);
 157                 spin_unlock(&vcpu->async_pf.lock);
 158
 159                 kvm_arch_async_page_ready(vcpu, work);
 160                 kvm_async_page_present_async(vcpu, work);
 161
 162                 list_del(&work->queue);
 163                 vcpu->async_pf.queued--;
 164                 kmem_cache_free(async_pf_cache, work);
 165         }
 166 }
 167
 168 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
 169                        struct kvm_arch_async_pf *arch)
 170 {
 171         struct kvm_async_pf *work;
 172
 173         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
 174                 return 0;
 175
 176         /* setup delayed work */
 177
 178         /*
 179          * do alloc nowait since if we are going to sleep anyway we
 180          * may as well sleep faulting in page
 181          */
 182         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
 183         if (!work)
 184                 return 0;
 185
 186         work->wakeup_all = false;
 187         work->vcpu = vcpu;
 188         work->gva = gva;
 189         work->addr = hva;
 190         work->arch = *arch;
 191         work->mm = current->mm;
 192         mmget(work->mm);
 193         kvm_get_kvm(work->vcpu->kvm);
 194
 195         /* this can't really happen otherwise gfn_to_pfn_async
 196            would succeed */
 197         if (unlikely(kvm_is_error_hva(work->addr)))
 198                 goto retry_sync;
 199
 200         INIT_WORK(&work->work, async_pf_execute);
 201         if (!schedule_work(&work->work))
 202                 goto retry_sync;
 203
 204         list_add_tail(&work->queue, &vcpu->async_pf.queue);
 205         vcpu->async_pf.queued++;
 206         kvm_arch_async_page_not_present(vcpu, work);
 207         return 1;
 208 retry_sync:
 209         kvm_put_kvm(work->vcpu->kvm);
 210         mmput(work->mm);
 211         kmem_cache_free(async_pf_cache, work);
 212         return 0;
 213 }
 214
 215 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 216 {
 217         struct kvm_async_pf *work;
 218
 219         if (!list_empty_careful(&vcpu->async_pf.done))
 220                 return 0;
 221
 222         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
 223         if (!work)
 224                 return -ENOMEM;
 225
 226         work->wakeup_all = true;
 227         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 228
 229         spin_lock(&vcpu->async_pf.lock);
 230         list_add_tail(&work->link, &vcpu->async_pf.done);
 231         spin_unlock(&vcpu->async_pf.lock);
 232
 233         vcpu->async_pf.queued++;
 234         return 0;
 235 }