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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 #include <linux/sched/mm.h>
 28 
 29 #include "async_pf.h"
 30 #include <trace/events/kvm.h>
 31 
 32 static inline void kvm_async_page_present_sync(struct kvm_vcpu *vcpu,
 33                                                struct kvm_async_pf *work)
 34 {
 35 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
 36         kvm_arch_async_page_present(vcpu, work);
 37 #endif
 38 }
 39 static inline void kvm_async_page_present_async(struct kvm_vcpu *vcpu,
 40                                                 struct kvm_async_pf *work)
 41 {
 42 #ifndef CONFIG_KVM_ASYNC_PF_SYNC
 43         kvm_arch_async_page_present(vcpu, work);
 44 #endif
 45 }
 46 
 47 static struct kmem_cache *async_pf_cache;
 48 
 49 int kvm_async_pf_init(void)
 50 {
 51         async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
 52 
 53         if (!async_pf_cache)
 54                 return -ENOMEM;
 55 
 56         return 0;
 57 }
 58 
 59 void kvm_async_pf_deinit(void)
 60 {
 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         int locked = 1;
 81 
 82         might_sleep();
 83 
 84         /*
 85          * This work is run asynchromously to the task which owns
 86          * mm and might be done in another context, so we must
 87          * access remotely.
 88          */
 89         down_read(&mm->mmap_sem);
 90         get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL,
 91                         &locked);
 92         if (locked)
 93                 up_read(&mm->mmap_sem);
 94 
 95         kvm_async_page_present_sync(vcpu, apf);
 96 
 97         spin_lock(&vcpu->async_pf.lock);
 98         list_add_tail(&apf->link, &vcpu->async_pf.done);
 99         apf->vcpu = NULL;
100         spin_unlock(&vcpu->async_pf.lock);
101 
102         /*
103          * apf may be freed by kvm_check_async_pf_completion() after
104          * this point
105          */
106 
107         trace_kvm_async_pf_completed(addr, gva);
108 
109         /*
110          * This memory barrier pairs with prepare_to_wait's set_current_state()
111          */
112         smp_mb();
113         if (swait_active(&vcpu->wq))
114                 swake_up(&vcpu->wq);
115 
116         mmput(mm);
117         kvm_put_kvm(vcpu->kvm);
118 }
119 
120 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
121 {
122         spin_lock(&vcpu->async_pf.lock);
123 
124         /* cancel outstanding work queue item */
125         while (!list_empty(&vcpu->async_pf.queue)) {
126                 struct kvm_async_pf *work =
127                         list_first_entry(&vcpu->async_pf.queue,
128                                          typeof(*work), queue);
129                 list_del(&work->queue);
130 
131                 /*
132                  * We know it's present in vcpu->async_pf.done, do
133                  * nothing here.
134                  */
135                 if (!work->vcpu)
136                         continue;
137 
138                 spin_unlock(&vcpu->async_pf.lock);
139 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
140                 flush_work(&work->work);
141 #else
142                 if (cancel_work_sync(&work->work)) {
143                         mmput(work->mm);
144                         kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
145                         kmem_cache_free(async_pf_cache, work);
146                 }
147 #endif
148                 spin_lock(&vcpu->async_pf.lock);
149         }
150 
151         while (!list_empty(&vcpu->async_pf.done)) {
152                 struct kvm_async_pf *work =
153                         list_first_entry(&vcpu->async_pf.done,
154                                          typeof(*work), link);
155                 list_del(&work->link);
156                 kmem_cache_free(async_pf_cache, work);
157         }
158         spin_unlock(&vcpu->async_pf.lock);
159 
160         vcpu->async_pf.queued = 0;
161 }
162 
163 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
164 {
165         struct kvm_async_pf *work;
166 
167         while (!list_empty_careful(&vcpu->async_pf.done) &&
168               kvm_arch_can_inject_async_page_present(vcpu)) {
169                 spin_lock(&vcpu->async_pf.lock);
170                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
171                                               link);
172                 list_del(&work->link);
173                 spin_unlock(&vcpu->async_pf.lock);
174 
175                 kvm_arch_async_page_ready(vcpu, work);
176                 kvm_async_page_present_async(vcpu, work);
177 
178                 list_del(&work->queue);
179                 vcpu->async_pf.queued--;
180                 kmem_cache_free(async_pf_cache, work);
181         }
182 }
183 
184 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
185                        struct kvm_arch_async_pf *arch)
186 {
187         struct kvm_async_pf *work;
188 
189         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
190                 return 0;
191 
192         /* setup delayed work */
193 
194         /*
195          * do alloc nowait since if we are going to sleep anyway we
196          * may as well sleep faulting in page
197          */
198         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
199         if (!work)
200                 return 0;
201 
202         work->wakeup_all = false;
203         work->vcpu = vcpu;
204         work->gva = gva;
205         work->addr = hva;
206         work->arch = *arch;
207         work->mm = current->mm;
208         mmget(work->mm);
209         kvm_get_kvm(work->vcpu->kvm);
210 
211         /* this can't really happen otherwise gfn_to_pfn_async
212            would succeed */
213         if (unlikely(kvm_is_error_hva(work->addr)))
214                 goto retry_sync;
215 
216         INIT_WORK(&work->work, async_pf_execute);
217         if (!schedule_work(&work->work))
218                 goto retry_sync;
219 
220         list_add_tail(&work->queue, &vcpu->async_pf.queue);
221         vcpu->async_pf.queued++;
222         kvm_arch_async_page_not_present(vcpu, work);
223         return 1;
224 retry_sync:
225         kvm_put_kvm(work->vcpu->kvm);
226         mmput(work->mm);
227         kmem_cache_free(async_pf_cache, work);
228         return 0;
229 }
230 
231 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
232 {
233         struct kvm_async_pf *work;
234 
235         if (!list_empty_careful(&vcpu->async_pf.done))
236                 return 0;
237 
238         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
239         if (!work)
240                 return -ENOMEM;
241 
242         work->wakeup_all = true;
243         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
244 
245         spin_lock(&vcpu->async_pf.lock);
246         list_add_tail(&work->link, &vcpu->async_pf.done);
247         spin_unlock(&vcpu->async_pf.lock);
248 
249         vcpu->async_pf.queued++;
250         return 0;
251 }
252 

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