Staging: comedi: fix mmap_count
[linux-2.6.git] / virt / kvm / async_pf.c
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
28 #include "async_pf.h"
29 #include <trace/events/kvm.h>
30
31 static struct kmem_cache *async_pf_cache;
32
33 int kvm_async_pf_init(void)
34 {
35         async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
36
37         if (!async_pf_cache)
38                 return -ENOMEM;
39
40         return 0;
41 }
42
43 void kvm_async_pf_deinit(void)
44 {
45         if (async_pf_cache)
46                 kmem_cache_destroy(async_pf_cache);
47         async_pf_cache = NULL;
48 }
49
50 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
51 {
52         INIT_LIST_HEAD(&vcpu->async_pf.done);
53         INIT_LIST_HEAD(&vcpu->async_pf.queue);
54         spin_lock_init(&vcpu->async_pf.lock);
55 }
56
57 static void async_pf_execute(struct work_struct *work)
58 {
59         struct page *page = NULL;
60         struct kvm_async_pf *apf =
61                 container_of(work, struct kvm_async_pf, work);
62         struct mm_struct *mm = apf->mm;
63         struct kvm_vcpu *vcpu = apf->vcpu;
64         unsigned long addr = apf->addr;
65         gva_t gva = apf->gva;
66
67         might_sleep();
68
69         use_mm(mm);
70         down_read(&mm->mmap_sem);
71         get_user_pages(current, mm, addr, 1, 1, 0, &page, NULL);
72         up_read(&mm->mmap_sem);
73         unuse_mm(mm);
74
75         spin_lock(&vcpu->async_pf.lock);
76         list_add_tail(&apf->link, &vcpu->async_pf.done);
77         apf->page = page;
78         apf->done = true;
79         spin_unlock(&vcpu->async_pf.lock);
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, page, gva);
87
88         if (waitqueue_active(&vcpu->wq))
89                 wake_up_interruptible(&vcpu->wq);
90
91         mmdrop(mm);
92         kvm_put_kvm(vcpu->kvm);
93 }
94
95 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
96 {
97         /* cancel outstanding work queue item */
98         while (!list_empty(&vcpu->async_pf.queue)) {
99                 struct kvm_async_pf *work =
100                         list_entry(vcpu->async_pf.queue.next,
101                                    typeof(*work), queue);
102                 cancel_work_sync(&work->work);
103                 list_del(&work->queue);
104                 if (!work->done) /* work was canceled */
105                         kmem_cache_free(async_pf_cache, work);
106         }
107
108         spin_lock(&vcpu->async_pf.lock);
109         while (!list_empty(&vcpu->async_pf.done)) {
110                 struct kvm_async_pf *work =
111                         list_entry(vcpu->async_pf.done.next,
112                                    typeof(*work), link);
113                 list_del(&work->link);
114                 if (work->page)
115                         put_page(work->page);
116                 kmem_cache_free(async_pf_cache, work);
117         }
118         spin_unlock(&vcpu->async_pf.lock);
119
120         vcpu->async_pf.queued = 0;
121 }
122
123 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
124 {
125         struct kvm_async_pf *work;
126
127         while (!list_empty_careful(&vcpu->async_pf.done) &&
128               kvm_arch_can_inject_async_page_present(vcpu)) {
129                 spin_lock(&vcpu->async_pf.lock);
130                 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
131                                               link);
132                 list_del(&work->link);
133                 spin_unlock(&vcpu->async_pf.lock);
134
135                 if (work->page)
136                         kvm_arch_async_page_ready(vcpu, work);
137                 kvm_arch_async_page_present(vcpu, work);
138
139                 list_del(&work->queue);
140                 vcpu->async_pf.queued--;
141                 if (work->page)
142                         put_page(work->page);
143                 kmem_cache_free(async_pf_cache, work);
144         }
145 }
146
147 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
148                        struct kvm_arch_async_pf *arch)
149 {
150         struct kvm_async_pf *work;
151
152         if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
153                 return 0;
154
155         /* setup delayed work */
156
157         /*
158          * do alloc nowait since if we are going to sleep anyway we
159          * may as well sleep faulting in page
160          */
161         work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
162         if (!work)
163                 return 0;
164
165         work->page = NULL;
166         work->done = false;
167         work->vcpu = vcpu;
168         work->gva = gva;
169         work->addr = gfn_to_hva(vcpu->kvm, gfn);
170         work->arch = *arch;
171         work->mm = current->mm;
172         atomic_inc(&work->mm->mm_count);
173         kvm_get_kvm(work->vcpu->kvm);
174
175         /* this can't really happen otherwise gfn_to_pfn_async
176            would succeed */
177         if (unlikely(kvm_is_error_hva(work->addr)))
178                 goto retry_sync;
179
180         INIT_WORK(&work->work, async_pf_execute);
181         if (!schedule_work(&work->work))
182                 goto retry_sync;
183
184         list_add_tail(&work->queue, &vcpu->async_pf.queue);
185         vcpu->async_pf.queued++;
186         kvm_arch_async_page_not_present(vcpu, work);
187         return 1;
188 retry_sync:
189         kvm_put_kvm(work->vcpu->kvm);
190         mmdrop(work->mm);
191         kmem_cache_free(async_pf_cache, work);
192         return 0;
193 }
194
195 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
196 {
197         struct kvm_async_pf *work;
198
199         if (!list_empty_careful(&vcpu->async_pf.done))
200                 return 0;
201
202         work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
203         if (!work)
204                 return -ENOMEM;
205
206         work->page = bad_page;
207         get_page(bad_page);
208         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
209
210         spin_lock(&vcpu->async_pf.lock);
211         list_add_tail(&work->link, &vcpu->async_pf.done);
212         spin_unlock(&vcpu->async_pf.lock);
213
214         vcpu->async_pf.queued++;
215         return 0;
216 }