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