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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
20static struct kmem_cache *async_pf_cache;
21
22int 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
32void kvm_async_pf_deinit(void)
33{
34 kmem_cache_destroy(async_pf_cache);
35 async_pf_cache = NULL;
36}
37
38void 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
45static 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 kvm_vcpu *vcpu = apf->vcpu;
50 struct mm_struct *mm = vcpu->kvm->mm;
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 * Attempt to pin the VM's host address space, and simply skip gup() if
60 * acquiring a pin fail, i.e. if the process is exiting. Note, KVM
61 * holds a reference to its associated mm_struct until the very end of
62 * kvm_destroy_vm(), i.e. the struct itself won't be freed before this
63 * work item is fully processed.
64 */
65 if (mmget_not_zero(mm)) {
66 mmap_read_lock(mm);
67 get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, &locked);
68 if (locked)
69 mmap_read_unlock(mm);
70 mmput(mm);
71 }
72
73 /*
74 * Notify and kick the vCPU even if faulting in the page failed, e.g.
75 * so that the vCPU can retry the fault synchronously.
76 */
77 if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
78 kvm_arch_async_page_present(vcpu, apf);
79
80 spin_lock(&vcpu->async_pf.lock);
81 first = list_empty(&vcpu->async_pf.done);
82 list_add_tail(&apf->link, &vcpu->async_pf.done);
83 spin_unlock(&vcpu->async_pf.lock);
84
85 /*
86 * The apf struct may be freed by kvm_check_async_pf_completion() as
87 * soon as the lock is dropped. Nullify it to prevent improper usage.
88 */
89 apf = NULL;
90
91 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
92 kvm_arch_async_page_present_queued(vcpu);
93
94 trace_kvm_async_pf_completed(addr, cr2_or_gpa);
95
96 __kvm_vcpu_wake_up(vcpu);
97}
98
99static void kvm_flush_and_free_async_pf_work(struct kvm_async_pf *work)
100{
101 /*
102 * The async #PF is "done", but KVM must wait for the work item itself,
103 * i.e. async_pf_execute(), to run to completion. If KVM is a module,
104 * KVM must ensure *no* code owned by the KVM (the module) can be run
105 * after the last call to module_put(). Note, flushing the work item
106 * is always required when the item is taken off the completion queue.
107 * E.g. even if the vCPU handles the item in the "normal" path, the VM
108 * could be terminated before async_pf_execute() completes.
109 *
110 * Wake all events skip the queue and go straight done, i.e. don't
111 * need to be flushed (but sanity check that the work wasn't queued).
112 */
113 if (work->wakeup_all)
114 WARN_ON_ONCE(work->work.func);
115 else
116 flush_work(&work->work);
117 kmem_cache_free(async_pf_cache, work);
118}
119
120void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
121{
122 /* cancel outstanding work queue item */
123 while (!list_empty(&vcpu->async_pf.queue)) {
124 struct kvm_async_pf *work =
125 list_first_entry(&vcpu->async_pf.queue,
126 typeof(*work), queue);
127 list_del(&work->queue);
128
129#ifdef CONFIG_KVM_ASYNC_PF_SYNC
130 flush_work(&work->work);
131#else
132 if (cancel_work_sync(&work->work))
133 kmem_cache_free(async_pf_cache, work);
134#endif
135 }
136
137 spin_lock(&vcpu->async_pf.lock);
138 while (!list_empty(&vcpu->async_pf.done)) {
139 struct kvm_async_pf *work =
140 list_first_entry(&vcpu->async_pf.done,
141 typeof(*work), link);
142 list_del(&work->link);
143
144 spin_unlock(&vcpu->async_pf.lock);
145 kvm_flush_and_free_async_pf_work(work);
146 spin_lock(&vcpu->async_pf.lock);
147 }
148 spin_unlock(&vcpu->async_pf.lock);
149
150 vcpu->async_pf.queued = 0;
151}
152
153void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
154{
155 struct kvm_async_pf *work;
156
157 while (!list_empty_careful(&vcpu->async_pf.done) &&
158 kvm_arch_can_dequeue_async_page_present(vcpu)) {
159 spin_lock(&vcpu->async_pf.lock);
160 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
161 link);
162 list_del(&work->link);
163 spin_unlock(&vcpu->async_pf.lock);
164
165 kvm_arch_async_page_ready(vcpu, work);
166 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
167 kvm_arch_async_page_present(vcpu, work);
168
169 list_del(&work->queue);
170 vcpu->async_pf.queued--;
171 kvm_flush_and_free_async_pf_work(work);
172 }
173}
174
175/*
176 * Try to schedule a job to handle page fault asynchronously. Returns 'true' on
177 * success, 'false' on failure (page fault has to be handled synchronously).
178 */
179bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
180 unsigned long hva, struct kvm_arch_async_pf *arch)
181{
182 struct kvm_async_pf *work;
183
184 if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
185 return false;
186
187 /* Arch specific code should not do async PF in this case */
188 if (unlikely(kvm_is_error_hva(hva)))
189 return false;
190
191 /*
192 * do alloc nowait since if we are going to sleep anyway we
193 * may as well sleep faulting in page
194 */
195 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
196 if (!work)
197 return false;
198
199 work->wakeup_all = false;
200 work->vcpu = vcpu;
201 work->cr2_or_gpa = cr2_or_gpa;
202 work->addr = hva;
203 work->arch = *arch;
204
205 INIT_WORK(&work->work, async_pf_execute);
206
207 list_add_tail(&work->queue, &vcpu->async_pf.queue);
208 vcpu->async_pf.queued++;
209 work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);
210
211 schedule_work(&work->work);
212
213 return true;
214}
215
216int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
217{
218 struct kvm_async_pf *work;
219 bool first;
220
221 if (!list_empty_careful(&vcpu->async_pf.done))
222 return 0;
223
224 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
225 if (!work)
226 return -ENOMEM;
227
228 work->wakeup_all = true;
229 INIT_LIST_HEAD(&work->queue); /* for list_del to work */
230
231 spin_lock(&vcpu->async_pf.lock);
232 first = list_empty(&vcpu->async_pf.done);
233 list_add_tail(&work->link, &vcpu->async_pf.done);
234 spin_unlock(&vcpu->async_pf.lock);
235
236 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
237 kvm_arch_async_page_present_queued(vcpu);
238
239 vcpu->async_pf.queued++;
240 return 0;
241}
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
32static 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}
39static 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
47static struct kmem_cache *async_pf_cache;
48
49int 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
59void kvm_async_pf_deinit(void)
60{
61 kmem_cache_destroy(async_pf_cache);
62 async_pf_cache = NULL;
63}
64
65void 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
72static 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 if (swq_has_sleeper(&vcpu->wq))
110 swake_up(&vcpu->wq);
111
112 mmput(mm);
113 kvm_put_kvm(vcpu->kvm);
114}
115
116void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
117{
118 spin_lock(&vcpu->async_pf.lock);
119
120 /* cancel outstanding work queue item */
121 while (!list_empty(&vcpu->async_pf.queue)) {
122 struct kvm_async_pf *work =
123 list_first_entry(&vcpu->async_pf.queue,
124 typeof(*work), queue);
125 list_del(&work->queue);
126
127 /*
128 * We know it's present in vcpu->async_pf.done, do
129 * nothing here.
130 */
131 if (!work->vcpu)
132 continue;
133
134 spin_unlock(&vcpu->async_pf.lock);
135#ifdef CONFIG_KVM_ASYNC_PF_SYNC
136 flush_work(&work->work);
137#else
138 if (cancel_work_sync(&work->work)) {
139 mmput(work->mm);
140 kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
141 kmem_cache_free(async_pf_cache, work);
142 }
143#endif
144 spin_lock(&vcpu->async_pf.lock);
145 }
146
147 while (!list_empty(&vcpu->async_pf.done)) {
148 struct kvm_async_pf *work =
149 list_first_entry(&vcpu->async_pf.done,
150 typeof(*work), link);
151 list_del(&work->link);
152 kmem_cache_free(async_pf_cache, work);
153 }
154 spin_unlock(&vcpu->async_pf.lock);
155
156 vcpu->async_pf.queued = 0;
157}
158
159void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
160{
161 struct kvm_async_pf *work;
162
163 while (!list_empty_careful(&vcpu->async_pf.done) &&
164 kvm_arch_can_inject_async_page_present(vcpu)) {
165 spin_lock(&vcpu->async_pf.lock);
166 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
167 link);
168 list_del(&work->link);
169 spin_unlock(&vcpu->async_pf.lock);
170
171 kvm_arch_async_page_ready(vcpu, work);
172 kvm_async_page_present_async(vcpu, work);
173
174 list_del(&work->queue);
175 vcpu->async_pf.queued--;
176 kmem_cache_free(async_pf_cache, work);
177 }
178}
179
180int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
181 struct kvm_arch_async_pf *arch)
182{
183 struct kvm_async_pf *work;
184
185 if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
186 return 0;
187
188 /* setup delayed work */
189
190 /*
191 * do alloc nowait since if we are going to sleep anyway we
192 * may as well sleep faulting in page
193 */
194 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
195 if (!work)
196 return 0;
197
198 work->wakeup_all = false;
199 work->vcpu = vcpu;
200 work->gva = gva;
201 work->addr = hva;
202 work->arch = *arch;
203 work->mm = current->mm;
204 mmget(work->mm);
205 kvm_get_kvm(work->vcpu->kvm);
206
207 /* this can't really happen otherwise gfn_to_pfn_async
208 would succeed */
209 if (unlikely(kvm_is_error_hva(work->addr)))
210 goto retry_sync;
211
212 INIT_WORK(&work->work, async_pf_execute);
213 if (!schedule_work(&work->work))
214 goto retry_sync;
215
216 list_add_tail(&work->queue, &vcpu->async_pf.queue);
217 vcpu->async_pf.queued++;
218 kvm_arch_async_page_not_present(vcpu, work);
219 return 1;
220retry_sync:
221 kvm_put_kvm(work->vcpu->kvm);
222 mmput(work->mm);
223 kmem_cache_free(async_pf_cache, work);
224 return 0;
225}
226
227int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
228{
229 struct kvm_async_pf *work;
230
231 if (!list_empty_careful(&vcpu->async_pf.done))
232 return 0;
233
234 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
235 if (!work)
236 return -ENOMEM;
237
238 work->wakeup_all = true;
239 INIT_LIST_HEAD(&work->queue); /* for list_del to work */
240
241 spin_lock(&vcpu->async_pf.lock);
242 list_add_tail(&work->link, &vcpu->async_pf.done);
243 spin_unlock(&vcpu->async_pf.lock);
244
245 vcpu->async_pf.queued++;
246 return 0;
247}