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 inline void kvm_async_page_present_sync(struct kvm_vcpu *vcpu, 32 struct kvm_async_pf *work) 33 { 34 #ifdef CONFIG_KVM_ASYNC_PF_SYNC 35 kvm_arch_async_page_present(vcpu, work); 36 #endif 37 } 38 static inline void kvm_async_page_present_async(struct kvm_vcpu *vcpu, 39 struct kvm_async_pf *work) 40 { 41 #ifndef CONFIG_KVM_ASYNC_PF_SYNC 42 kvm_arch_async_page_present(vcpu, work); 43 #endif 44 } 45 46 static struct kmem_cache *async_pf_cache; 47 48 int kvm_async_pf_init(void) 49 { 50 async_pf_cache = KMEM_CACHE(kvm_async_pf, 0); 51 52 if (!async_pf_cache) 53 return -ENOMEM; 54 55 return 0; 56 } 57 58 void kvm_async_pf_deinit(void) 59 { 60 kmem_cache_destroy(async_pf_cache); 61 async_pf_cache = NULL; 62 } 63 64 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu) 65 { 66 INIT_LIST_HEAD(&vcpu->async_pf.done); 67 INIT_LIST_HEAD(&vcpu->async_pf.queue); 68 spin_lock_init(&vcpu->async_pf.lock); 69 } 70 71 static void async_pf_execute(struct work_struct *work) 72 { 73 struct kvm_async_pf *apf = 74 container_of(work, struct kvm_async_pf, work); 75 struct mm_struct *mm = apf->mm; 76 struct kvm_vcpu *vcpu = apf->vcpu; 77 unsigned long addr = apf->addr; 78 gva_t gva = apf->gva; 79 int locked = 1; 80 81 might_sleep(); 82 83 /* 84 * This work is run asynchromously to the task which owns 85 * mm and might be done in another context, so we must 86 * access remotely. 87 */ 88 down_read(&mm->mmap_sem); 89 get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL, 90 &locked); 91 if (locked) 92 up_read(&mm->mmap_sem); 93 94 kvm_async_page_present_sync(vcpu, apf); 95 96 spin_lock(&vcpu->async_pf.lock); 97 list_add_tail(&apf->link, &vcpu->async_pf.done); 98 apf->vcpu = NULL; 99 spin_unlock(&vcpu->async_pf.lock); 100 101 /* 102 * apf may be freed by kvm_check_async_pf_completion() after 103 * this point 104 */ 105 106 trace_kvm_async_pf_completed(addr, gva); 107 108 /* 109 * This memory barrier pairs with prepare_to_wait's set_current_state() 110 */ 111 smp_mb(); 112 if (swait_active(&vcpu->wq)) 113 swake_up(&vcpu->wq); 114 115 mmput(mm); 116 kvm_put_kvm(vcpu->kvm); 117 } 118 119 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) 120 { 121 spin_lock(&vcpu->async_pf.lock); 122 123 /* cancel outstanding work queue item */ 124 while (!list_empty(&vcpu->async_pf.queue)) { 125 struct kvm_async_pf *work = 126 list_first_entry(&vcpu->async_pf.queue, 127 typeof(*work), queue); 128 list_del(&work->queue); 129 130 /* 131 * We know it's present in vcpu->async_pf.done, do 132 * nothing here. 133 */ 134 if (!work->vcpu) 135 continue; 136 137 spin_unlock(&vcpu->async_pf.lock); 138 #ifdef CONFIG_KVM_ASYNC_PF_SYNC 139 flush_work(&work->work); 140 #else 141 if (cancel_work_sync(&work->work)) { 142 mmput(work->mm); 143 kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */ 144 kmem_cache_free(async_pf_cache, work); 145 } 146 #endif 147 spin_lock(&vcpu->async_pf.lock); 148 } 149 150 while (!list_empty(&vcpu->async_pf.done)) { 151 struct kvm_async_pf *work = 152 list_first_entry(&vcpu->async_pf.done, 153 typeof(*work), link); 154 list_del(&work->link); 155 kmem_cache_free(async_pf_cache, work); 156 } 157 spin_unlock(&vcpu->async_pf.lock); 158 159 vcpu->async_pf.queued = 0; 160 } 161 162 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) 163 { 164 struct kvm_async_pf *work; 165 166 while (!list_empty_careful(&vcpu->async_pf.done) && 167 kvm_arch_can_inject_async_page_present(vcpu)) { 168 spin_lock(&vcpu->async_pf.lock); 169 work = list_first_entry(&vcpu->async_pf.done, typeof(*work), 170 link); 171 list_del(&work->link); 172 spin_unlock(&vcpu->async_pf.lock); 173 174 kvm_arch_async_page_ready(vcpu, work); 175 kvm_async_page_present_async(vcpu, work); 176 177 list_del(&work->queue); 178 vcpu->async_pf.queued--; 179 kmem_cache_free(async_pf_cache, work); 180 } 181 } 182 183 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva, 184 struct kvm_arch_async_pf *arch) 185 { 186 struct kvm_async_pf *work; 187 188 if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU) 189 return 0; 190 191 /* setup delayed work */ 192 193 /* 194 * do alloc nowait since if we are going to sleep anyway we 195 * may as well sleep faulting in page 196 */ 197 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN); 198 if (!work) 199 return 0; 200 201 work->wakeup_all = false; 202 work->vcpu = vcpu; 203 work->gva = gva; 204 work->addr = hva; 205 work->arch = *arch; 206 work->mm = current->mm; 207 atomic_inc(&work->mm->mm_users); 208 kvm_get_kvm(work->vcpu->kvm); 209 210 /* this can't really happen otherwise gfn_to_pfn_async 211 would succeed */ 212 if (unlikely(kvm_is_error_hva(work->addr))) 213 goto retry_sync; 214 215 INIT_WORK(&work->work, async_pf_execute); 216 if (!schedule_work(&work->work)) 217 goto retry_sync; 218 219 list_add_tail(&work->queue, &vcpu->async_pf.queue); 220 vcpu->async_pf.queued++; 221 kvm_arch_async_page_not_present(vcpu, work); 222 return 1; 223 retry_sync: 224 kvm_put_kvm(work->vcpu->kvm); 225 mmput(work->mm); 226 kmem_cache_free(async_pf_cache, work); 227 return 0; 228 } 229 230 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu) 231 { 232 struct kvm_async_pf *work; 233 234 if (!list_empty_careful(&vcpu->async_pf.done)) 235 return 0; 236 237 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC); 238 if (!work) 239 return -ENOMEM; 240 241 work->wakeup_all = true; 242 INIT_LIST_HEAD(&work->queue); /* for list_del to work */ 243 244 spin_lock(&vcpu->async_pf.lock); 245 list_add_tail(&work->link, &vcpu->async_pf.done); 246 spin_unlock(&vcpu->async_pf.lock); 247 248 vcpu->async_pf.queued++; 249 return 0; 250 } 251