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 struct kmem_cache *async_pf_cache;
21
kvm_async_pf_init(void)22 int 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
kvm_async_pf_deinit(void)32 void kvm_async_pf_deinit(void)
33 {
34 kmem_cache_destroy(async_pf_cache);
35 async_pf_cache = NULL;
36 }
37
kvm_async_pf_vcpu_init(struct kvm_vcpu * vcpu)38 void 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
async_pf_execute(struct work_struct * work)45 static 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 rcuwait_wake_up(&vcpu->wait);
89
90 mmput(mm);
91 kvm_put_kvm(vcpu->kvm);
92 }
93
kvm_clear_async_pf_completion_queue(struct kvm_vcpu * vcpu)94 void 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
kvm_check_async_pf_completion(struct kvm_vcpu * vcpu)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_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 */
kvm_setup_async_pf(struct kvm_vcpu * vcpu,gpa_t cr2_or_gpa,unsigned long hva,struct kvm_arch_async_pf * arch)163 bool 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
kvm_async_pf_wakeup_all(struct kvm_vcpu * vcpu)203 int 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 }
229