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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 apf->vcpu = NULL;
84 spin_unlock(&vcpu->async_pf.lock);
85
86 /*
87 * The apf struct may be freed by kvm_check_async_pf_completion() as
88 * soon as the lock is dropped. Nullify it to prevent improper usage.
89 */
90 apf = NULL;
91
92 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
93 kvm_arch_async_page_present_queued(vcpu);
94
95 trace_kvm_async_pf_completed(addr, cr2_or_gpa);
96
97 __kvm_vcpu_wake_up(vcpu);
98}
99
100static void kvm_flush_and_free_async_pf_work(struct kvm_async_pf *work)
101{
102 /*
103 * The async #PF is "done", but KVM must wait for the work item itself,
104 * i.e. async_pf_execute(), to run to completion. If KVM is a module,
105 * KVM must ensure *no* code owned by the KVM (the module) can be run
106 * after the last call to module_put(). Note, flushing the work item
107 * is always required when the item is taken off the completion queue.
108 * E.g. even if the vCPU handles the item in the "normal" path, the VM
109 * could be terminated before async_pf_execute() completes.
110 *
111 * Wake all events skip the queue and go straight done, i.e. don't
112 * need to be flushed (but sanity check that the work wasn't queued).
113 */
114 if (work->wakeup_all)
115 WARN_ON_ONCE(work->work.func);
116 else
117 flush_work(&work->work);
118 kmem_cache_free(async_pf_cache, work);
119}
120
121void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
122{
123 spin_lock(&vcpu->async_pf.lock);
124
125 /* cancel outstanding work queue item */
126 while (!list_empty(&vcpu->async_pf.queue)) {
127 struct kvm_async_pf *work =
128 list_first_entry(&vcpu->async_pf.queue,
129 typeof(*work), queue);
130 list_del(&work->queue);
131
132 /*
133 * We know it's present in vcpu->async_pf.done, do
134 * nothing here.
135 */
136 if (!work->vcpu)
137 continue;
138
139 spin_unlock(&vcpu->async_pf.lock);
140#ifdef CONFIG_KVM_ASYNC_PF_SYNC
141 flush_work(&work->work);
142#else
143 if (cancel_work_sync(&work->work))
144 kmem_cache_free(async_pf_cache, work);
145#endif
146 spin_lock(&vcpu->async_pf.lock);
147 }
148
149 while (!list_empty(&vcpu->async_pf.done)) {
150 struct kvm_async_pf *work =
151 list_first_entry(&vcpu->async_pf.done,
152 typeof(*work), link);
153 list_del(&work->link);
154
155 spin_unlock(&vcpu->async_pf.lock);
156 kvm_flush_and_free_async_pf_work(work);
157 spin_lock(&vcpu->async_pf.lock);
158 }
159 spin_unlock(&vcpu->async_pf.lock);
160
161 vcpu->async_pf.queued = 0;
162}
163
164void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
165{
166 struct kvm_async_pf *work;
167
168 while (!list_empty_careful(&vcpu->async_pf.done) &&
169 kvm_arch_can_dequeue_async_page_present(vcpu)) {
170 spin_lock(&vcpu->async_pf.lock);
171 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
172 link);
173 list_del(&work->link);
174 spin_unlock(&vcpu->async_pf.lock);
175
176 kvm_arch_async_page_ready(vcpu, work);
177 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
178 kvm_arch_async_page_present(vcpu, work);
179
180 list_del(&work->queue);
181 vcpu->async_pf.queued--;
182 kvm_flush_and_free_async_pf_work(work);
183 }
184}
185
186/*
187 * Try to schedule a job to handle page fault asynchronously. Returns 'true' on
188 * success, 'false' on failure (page fault has to be handled synchronously).
189 */
190bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
191 unsigned long hva, struct kvm_arch_async_pf *arch)
192{
193 struct kvm_async_pf *work;
194
195 if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
196 return false;
197
198 /* Arch specific code should not do async PF in this case */
199 if (unlikely(kvm_is_error_hva(hva)))
200 return false;
201
202 /*
203 * do alloc nowait since if we are going to sleep anyway we
204 * may as well sleep faulting in page
205 */
206 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
207 if (!work)
208 return false;
209
210 work->wakeup_all = false;
211 work->vcpu = vcpu;
212 work->cr2_or_gpa = cr2_or_gpa;
213 work->addr = hva;
214 work->arch = *arch;
215
216 INIT_WORK(&work->work, async_pf_execute);
217
218 list_add_tail(&work->queue, &vcpu->async_pf.queue);
219 vcpu->async_pf.queued++;
220 work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);
221
222 schedule_work(&work->work);
223
224 return true;
225}
226
227int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
228{
229 struct kvm_async_pf *work;
230 bool first;
231
232 if (!list_empty_careful(&vcpu->async_pf.done))
233 return 0;
234
235 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
236 if (!work)
237 return -ENOMEM;
238
239 work->wakeup_all = true;
240 INIT_LIST_HEAD(&work->queue); /* for list_del to work */
241
242 spin_lock(&vcpu->async_pf.lock);
243 first = list_empty(&vcpu->async_pf.done);
244 list_add_tail(&work->link, &vcpu->async_pf.done);
245 spin_unlock(&vcpu->async_pf.lock);
246
247 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
248 kvm_arch_async_page_present_queued(vcpu);
249
250 vcpu->async_pf.queued++;
251 return 0;
252}
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 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, NULL,
65 &locked);
66 if (locked)
67 mmap_read_unlock(mm);
68
69 if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
70 kvm_arch_async_page_present(vcpu, apf);
71
72 spin_lock(&vcpu->async_pf.lock);
73 first = list_empty(&vcpu->async_pf.done);
74 list_add_tail(&apf->link, &vcpu->async_pf.done);
75 apf->vcpu = NULL;
76 spin_unlock(&vcpu->async_pf.lock);
77
78 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
79 kvm_arch_async_page_present_queued(vcpu);
80
81 /*
82 * apf may be freed by kvm_check_async_pf_completion() after
83 * this point
84 */
85
86 trace_kvm_async_pf_completed(addr, cr2_or_gpa);
87
88 __kvm_vcpu_wake_up(vcpu);
89
90 mmput(mm);
91 kvm_put_kvm(vcpu->kvm);
92}
93
94void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
95{
96 spin_lock(&vcpu->async_pf.lock);
97
98 /* cancel outstanding work queue item */
99 while (!list_empty(&vcpu->async_pf.queue)) {
100 struct kvm_async_pf *work =
101 list_first_entry(&vcpu->async_pf.queue,
102 typeof(*work), queue);
103 list_del(&work->queue);
104
105 /*
106 * We know it's present in vcpu->async_pf.done, do
107 * nothing here.
108 */
109 if (!work->vcpu)
110 continue;
111
112 spin_unlock(&vcpu->async_pf.lock);
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 spin_lock(&vcpu->async_pf.lock);
123 }
124
125 while (!list_empty(&vcpu->async_pf.done)) {
126 struct kvm_async_pf *work =
127 list_first_entry(&vcpu->async_pf.done,
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
137void 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_dequeue_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 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
151 kvm_arch_async_page_present(vcpu, work);
152
153 list_del(&work->queue);
154 vcpu->async_pf.queued--;
155 kmem_cache_free(async_pf_cache, work);
156 }
157}
158
159/*
160 * Try to schedule a job to handle page fault asynchronously. Returns 'true' on
161 * success, 'false' on failure (page fault has to be handled synchronously).
162 */
163bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
164 unsigned long hva, struct kvm_arch_async_pf *arch)
165{
166 struct kvm_async_pf *work;
167
168 if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
169 return false;
170
171 /* Arch specific code should not do async PF in this case */
172 if (unlikely(kvm_is_error_hva(hva)))
173 return false;
174
175 /*
176 * do alloc nowait since if we are going to sleep anyway we
177 * may as well sleep faulting in page
178 */
179 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
180 if (!work)
181 return false;
182
183 work->wakeup_all = false;
184 work->vcpu = vcpu;
185 work->cr2_or_gpa = cr2_or_gpa;
186 work->addr = hva;
187 work->arch = *arch;
188 work->mm = current->mm;
189 mmget(work->mm);
190 kvm_get_kvm(work->vcpu->kvm);
191
192 INIT_WORK(&work->work, async_pf_execute);
193
194 list_add_tail(&work->queue, &vcpu->async_pf.queue);
195 vcpu->async_pf.queued++;
196 work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);
197
198 schedule_work(&work->work);
199
200 return true;
201}
202
203int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
204{
205 struct kvm_async_pf *work;
206 bool first;
207
208 if (!list_empty_careful(&vcpu->async_pf.done))
209 return 0;
210
211 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
212 if (!work)
213 return -ENOMEM;
214
215 work->wakeup_all = true;
216 INIT_LIST_HEAD(&work->queue); /* for list_del to work */
217
218 spin_lock(&vcpu->async_pf.lock);
219 first = list_empty(&vcpu->async_pf.done);
220 list_add_tail(&work->link, &vcpu->async_pf.done);
221 spin_unlock(&vcpu->async_pf.lock);
222
223 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
224 kvm_arch_async_page_present_queued(vcpu);
225
226 vcpu->async_pf.queued++;
227 return 0;
228}