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Linux/virt/kvm/async_pf.c

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  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         if (async_pf_cache)
 61                 kmem_cache_destroy(async_pf_cache);
 62         async_pf_cache = NULL;
 63 }
 64 
 65 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
 66 {
 67         INIT_LIST_HEAD(&vcpu->async_pf.done);
 68         INIT_LIST_HEAD(&vcpu->async_pf.queue);
 69         spin_lock_init(&vcpu->async_pf.lock);
 70 }
 71 
 72 static void async_pf_execute(struct work_struct *work)
 73 {
 74         struct kvm_async_pf *apf =
 75                 container_of(work, struct kvm_async_pf, work);
 76         struct mm_struct *mm = apf->mm;
 77         struct kvm_vcpu *vcpu = apf->vcpu;
 78         unsigned long addr = apf->addr;
 79         gva_t gva = apf->gva;
 80 
 81         might_sleep();
 82 
 83         get_user_pages_unlocked(NULL, mm, addr, 1, 1, 0, NULL);
 84         kvm_async_page_present_sync(vcpu, apf);
 85 
 86         spin_lock(&vcpu->async_pf.lock);
 87         list_add_tail(&apf->link, &vcpu->async_pf.done);
 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 (waitqueue_active(&vcpu->wq))
 98                 wake_up_interruptible(&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         /* cancel outstanding work queue item */
107         while (!list_empty(&vcpu->async_pf.queue)) {
108                 struct kvm_async_pf *work =
109                         list_entry(vcpu->async_pf.queue.next,
110                                    typeof(*work), queue);
111                 list_del(&work->queue);
112 
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         }
123 
124         spin_lock(&vcpu->async_pf.lock);
125         while (!list_empty(&vcpu->async_pf.done)) {
126                 struct kvm_async_pf *work =
127                         list_entry(vcpu->async_pf.done.next,
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_inject_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                 kvm_async_page_present_async(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 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
159                        struct kvm_arch_async_pf *arch)
160 {
161         struct kvm_async_pf *work;
162 
163         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
164                 return 0;
165 
166         /* setup delayed work */
167 
168         /*
169          * do alloc nowait since if we are going to sleep anyway we
170          * may as well sleep faulting in page
171          */
172         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
173         if (!work)
174                 return 0;
175 
176         work->wakeup_all = false;
177         work->vcpu = vcpu;
178         work->gva = gva;
179         work->addr = hva;
180         work->arch = *arch;
181         work->mm = current->mm;
182         atomic_inc(&work->mm->mm_users);
183         kvm_get_kvm(work->vcpu->kvm);
184 
185         /* this can't really happen otherwise gfn_to_pfn_async
186            would succeed */
187         if (unlikely(kvm_is_error_hva(work->addr)))
188                 goto retry_sync;
189 
190         INIT_WORK(&work->work, async_pf_execute);
191         if (!schedule_work(&work->work))
192                 goto retry_sync;
193 
194         list_add_tail(&work->queue, &vcpu->async_pf.queue);
195         vcpu->async_pf.queued++;
196         kvm_arch_async_page_not_present(vcpu, work);
197         return 1;
198 retry_sync:
199         kvm_put_kvm(work->vcpu->kvm);
200         mmput(work->mm);
201         kmem_cache_free(async_pf_cache, work);
202         return 0;
203 }
204 
205 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
206 {
207         struct kvm_async_pf *work;
208 
209         if (!list_empty_careful(&vcpu->async_pf.done))
210                 return 0;
211 
212         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
213         if (!work)
214                 return -ENOMEM;
215 
216         work->wakeup_all = true;
217         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
218 
219         spin_lock(&vcpu->async_pf.lock);
220         list_add_tail(&work->link, &vcpu->async_pf.done);
221         spin_unlock(&vcpu->async_pf.lock);
222 
223         vcpu->async_pf.queued++;
224         return 0;
225 }
226 

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