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
kvm_async_page_present_sync(struct kvm_vcpu * vcpu,struct kvm_async_pf * work)20 static inline void kvm_async_page_present_sync(struct kvm_vcpu *vcpu,
21 struct kvm_async_pf *work)
22 {
23 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
24 kvm_arch_async_page_present(vcpu, work);
25 #endif
26 }
kvm_async_page_present_async(struct kvm_vcpu * vcpu,struct kvm_async_pf * work)27 static inline void kvm_async_page_present_async(struct kvm_vcpu *vcpu,
28 struct kvm_async_pf *work)
29 {
30 #ifndef CONFIG_KVM_ASYNC_PF_SYNC
31 kvm_arch_async_page_present(vcpu, work);
32 #endif
33 }
34
35 static struct kmem_cache *async_pf_cache;
36
kvm_async_pf_init(void)37 int kvm_async_pf_init(void)
38 {
39 async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
40
41 if (!async_pf_cache)
42 return -ENOMEM;
43
44 return 0;
45 }
46
kvm_async_pf_deinit(void)47 void kvm_async_pf_deinit(void)
48 {
49 kmem_cache_destroy(async_pf_cache);
50 async_pf_cache = NULL;
51 }
52
kvm_async_pf_vcpu_init(struct kvm_vcpu * vcpu)53 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
54 {
55 INIT_LIST_HEAD(&vcpu->async_pf.done);
56 INIT_LIST_HEAD(&vcpu->async_pf.queue);
57 spin_lock_init(&vcpu->async_pf.lock);
58 }
59
async_pf_execute(struct work_struct * work)60 static void async_pf_execute(struct work_struct *work)
61 {
62 struct kvm_async_pf *apf =
63 container_of(work, struct kvm_async_pf, work);
64 struct mm_struct *mm = apf->mm;
65 struct kvm_vcpu *vcpu = apf->vcpu;
66 unsigned long addr = apf->addr;
67 gva_t gva = apf->gva;
68 int locked = 1;
69
70 might_sleep();
71
72 /*
73 * This work is run asynchronously to the task which owns
74 * mm and might be done in another context, so we must
75 * access remotely.
76 */
77 down_read(&mm->mmap_sem);
78 get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL,
79 &locked);
80 if (locked)
81 up_read(&mm->mmap_sem);
82
83 kvm_async_page_present_sync(vcpu, apf);
84
85 spin_lock(&vcpu->async_pf.lock);
86 list_add_tail(&apf->link, &vcpu->async_pf.done);
87 apf->vcpu = NULL;
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 (swq_has_sleeper(&vcpu->wq))
98 swake_up_one(&vcpu->wq);
99
100 mmput(mm);
101 kvm_put_kvm(vcpu->kvm);
102 }
103
kvm_clear_async_pf_completion_queue(struct kvm_vcpu * vcpu)104 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
105 {
106 spin_lock(&vcpu->async_pf.lock);
107
108 /* cancel outstanding work queue item */
109 while (!list_empty(&vcpu->async_pf.queue)) {
110 struct kvm_async_pf *work =
111 list_first_entry(&vcpu->async_pf.queue,
112 typeof(*work), queue);
113 list_del(&work->queue);
114
115 /*
116 * We know it's present in vcpu->async_pf.done, do
117 * nothing here.
118 */
119 if (!work->vcpu)
120 continue;
121
122 spin_unlock(&vcpu->async_pf.lock);
123 #ifdef CONFIG_KVM_ASYNC_PF_SYNC
124 flush_work(&work->work);
125 #else
126 if (cancel_work_sync(&work->work)) {
127 mmput(work->mm);
128 kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
129 kmem_cache_free(async_pf_cache, work);
130 }
131 #endif
132 spin_lock(&vcpu->async_pf.lock);
133 }
134
135 while (!list_empty(&vcpu->async_pf.done)) {
136 struct kvm_async_pf *work =
137 list_first_entry(&vcpu->async_pf.done,
138 typeof(*work), link);
139 list_del(&work->link);
140 kmem_cache_free(async_pf_cache, work);
141 }
142 spin_unlock(&vcpu->async_pf.lock);
143
144 vcpu->async_pf.queued = 0;
145 }
146
kvm_check_async_pf_completion(struct kvm_vcpu * vcpu)147 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
148 {
149 struct kvm_async_pf *work;
150
151 while (!list_empty_careful(&vcpu->async_pf.done) &&
152 kvm_arch_can_inject_async_page_present(vcpu)) {
153 spin_lock(&vcpu->async_pf.lock);
154 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
155 link);
156 list_del(&work->link);
157 spin_unlock(&vcpu->async_pf.lock);
158
159 kvm_arch_async_page_ready(vcpu, work);
160 kvm_async_page_present_async(vcpu, work);
161
162 list_del(&work->queue);
163 vcpu->async_pf.queued--;
164 kmem_cache_free(async_pf_cache, work);
165 }
166 }
167
kvm_setup_async_pf(struct kvm_vcpu * vcpu,gva_t gva,unsigned long hva,struct kvm_arch_async_pf * arch)168 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
169 struct kvm_arch_async_pf *arch)
170 {
171 struct kvm_async_pf *work;
172
173 if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
174 return 0;
175
176 /* setup delayed work */
177
178 /*
179 * do alloc nowait since if we are going to sleep anyway we
180 * may as well sleep faulting in page
181 */
182 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
183 if (!work)
184 return 0;
185
186 work->wakeup_all = false;
187 work->vcpu = vcpu;
188 work->gva = gva;
189 work->addr = hva;
190 work->arch = *arch;
191 work->mm = current->mm;
192 mmget(work->mm);
193 kvm_get_kvm(work->vcpu->kvm);
194
195 /* this can't really happen otherwise gfn_to_pfn_async
196 would succeed */
197 if (unlikely(kvm_is_error_hva(work->addr)))
198 goto retry_sync;
199
200 INIT_WORK(&work->work, async_pf_execute);
201 if (!schedule_work(&work->work))
202 goto retry_sync;
203
204 list_add_tail(&work->queue, &vcpu->async_pf.queue);
205 vcpu->async_pf.queued++;
206 kvm_arch_async_page_not_present(vcpu, work);
207 return 1;
208 retry_sync:
209 kvm_put_kvm(work->vcpu->kvm);
210 mmput(work->mm);
211 kmem_cache_free(async_pf_cache, work);
212 return 0;
213 }
214
kvm_async_pf_wakeup_all(struct kvm_vcpu * vcpu)215 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
216 {
217 struct kvm_async_pf *work;
218
219 if (!list_empty_careful(&vcpu->async_pf.done))
220 return 0;
221
222 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
223 if (!work)
224 return -ENOMEM;
225
226 work->wakeup_all = true;
227 INIT_LIST_HEAD(&work->queue); /* for list_del to work */
228
229 spin_lock(&vcpu->async_pf.lock);
230 list_add_tail(&work->link, &vcpu->async_pf.done);
231 spin_unlock(&vcpu->async_pf.lock);
232
233 vcpu->async_pf.queued++;
234 return 0;
235 }
236