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 #include <linux/sched/mm.h> 28 29 #include "async_pf.h" 30 #include <trace/events/kvm.h> 31 32 static inline void kvm_async_page_present_sync(struct kvm_vcpu *vcpu, 33 struct kvm_async_pf *work) 34 { 35 #ifdef CONFIG_KVM_ASYNC_PF_SYNC 36 kvm_arch_async_page_present(vcpu, work); 37 #endif 38 } 39 static inline void kvm_async_page_present_async(struct kvm_vcpu *vcpu, 40 struct kvm_async_pf *work) 41 { 42 #ifndef CONFIG_KVM_ASYNC_PF_SYNC 43 kvm_arch_async_page_present(vcpu, work); 44 #endif 45 } 46 47 static struct kmem_cache *async_pf_cache; 48 49 int kvm_async_pf_init(void) 50 { 51 async_pf_cache = KMEM_CACHE(kvm_async_pf, 0); 52 53 if (!async_pf_cache) 54 return -ENOMEM; 55 56 return 0; 57 } 58 59 void kvm_async_pf_deinit(void) 60 { 61 kmem_cache_destroy(async_pf_cache); 62 async_pf_cache = NULL; 63 } 64 65 void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu) 66 { 67 INIT_LIST_HEAD(&vcpu->async_pf.done); 68 INIT_LIST_HEAD(&vcpu->async_pf.queue); 69 spin_lock_init(&vcpu->async_pf.lock); 70 } 71 72 static void async_pf_execute(struct work_struct *work) 73 { 74 struct kvm_async_pf *apf = 75 container_of(work, struct kvm_async_pf, work); 76 struct mm_struct *mm = apf->mm; 77 struct kvm_vcpu *vcpu = apf->vcpu; 78 unsigned long addr = apf->addr; 79 gva_t gva = apf->gva; 80 int locked = 1; 81 82 might_sleep(); 83 84 /* 85 * This work is run asynchromously to the task which owns 86 * mm and might be done in another context, so we must 87 * access remotely. 88 */ 89 down_read(&mm->mmap_sem); 90 get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL, 91 &locked); 92 if (locked) 93 up_read(&mm->mmap_sem); 94 95 kvm_async_page_present_sync(vcpu, apf); 96 97 spin_lock(&vcpu->async_pf.lock); 98 list_add_tail(&apf->link, &vcpu->async_pf.done); 99 apf->vcpu = NULL; 100 spin_unlock(&vcpu->async_pf.lock); 101 102 /* 103 * apf may be freed by kvm_check_async_pf_completion() after 104 * this point 105 */ 106 107 trace_kvm_async_pf_completed(addr, gva); 108 109 /* 110 * This memory barrier pairs with prepare_to_wait's set_current_state() 111 */ 112 smp_mb(); 113 if (swait_active(&vcpu->wq)) 114 swake_up(&vcpu->wq); 115 116 mmput(mm); 117 kvm_put_kvm(vcpu->kvm); 118 } 119 120 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) 121 { 122 spin_lock(&vcpu->async_pf.lock); 123 124 /* cancel outstanding work queue item */ 125 while (!list_empty(&vcpu->async_pf.queue)) { 126 struct kvm_async_pf *work = 127 list_first_entry(&vcpu->async_pf.queue, 128 typeof(*work), queue); 129 list_del(&work->queue); 130 131 /* 132 * We know it's present in vcpu->async_pf.done, do 133 * nothing here. 134 */ 135 if (!work->vcpu) 136 continue; 137 138 spin_unlock(&vcpu->async_pf.lock); 139 #ifdef CONFIG_KVM_ASYNC_PF_SYNC 140 flush_work(&work->work); 141 #else 142 if (cancel_work_sync(&work->work)) { 143 mmput(work->mm); 144 kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */ 145 kmem_cache_free(async_pf_cache, work); 146 } 147 #endif 148 spin_lock(&vcpu->async_pf.lock); 149 } 150 151 while (!list_empty(&vcpu->async_pf.done)) { 152 struct kvm_async_pf *work = 153 list_first_entry(&vcpu->async_pf.done, 154 typeof(*work), link); 155 list_del(&work->link); 156 kmem_cache_free(async_pf_cache, work); 157 } 158 spin_unlock(&vcpu->async_pf.lock); 159 160 vcpu->async_pf.queued = 0; 161 } 162 163 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) 164 { 165 struct kvm_async_pf *work; 166 167 while (!list_empty_careful(&vcpu->async_pf.done) && 168 kvm_arch_can_inject_async_page_present(vcpu)) { 169 spin_lock(&vcpu->async_pf.lock); 170 work = list_first_entry(&vcpu->async_pf.done, typeof(*work), 171 link); 172 list_del(&work->link); 173 spin_unlock(&vcpu->async_pf.lock); 174 175 kvm_arch_async_page_ready(vcpu, work); 176 kvm_async_page_present_async(vcpu, work); 177 178 list_del(&work->queue); 179 vcpu->async_pf.queued--; 180 kmem_cache_free(async_pf_cache, work); 181 } 182 } 183 184 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva, 185 struct kvm_arch_async_pf *arch) 186 { 187 struct kvm_async_pf *work; 188 189 if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU) 190 return 0; 191 192 /* setup delayed work */ 193 194 /* 195 * do alloc nowait since if we are going to sleep anyway we 196 * may as well sleep faulting in page 197 */ 198 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN); 199 if (!work) 200 return 0; 201 202 work->wakeup_all = false; 203 work->vcpu = vcpu; 204 work->gva = gva; 205 work->addr = hva; 206 work->arch = *arch; 207 work->mm = current->mm; 208 mmget(work->mm); 209 kvm_get_kvm(work->vcpu->kvm); 210 211 /* this can't really happen otherwise gfn_to_pfn_async 212 would succeed */ 213 if (unlikely(kvm_is_error_hva(work->addr))) 214 goto retry_sync; 215 216 INIT_WORK(&work->work, async_pf_execute); 217 if (!schedule_work(&work->work)) 218 goto retry_sync; 219 220 list_add_tail(&work->queue, &vcpu->async_pf.queue); 221 vcpu->async_pf.queued++; 222 kvm_arch_async_page_not_present(vcpu, work); 223 return 1; 224 retry_sync: 225 kvm_put_kvm(work->vcpu->kvm); 226 mmput(work->mm); 227 kmem_cache_free(async_pf_cache, work); 228 return 0; 229 } 230 231 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu) 232 { 233 struct kvm_async_pf *work; 234 235 if (!list_empty_careful(&vcpu->async_pf.done)) 236 return 0; 237 238 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC); 239 if (!work) 240 return -ENOMEM; 241 242 work->wakeup_all = true; 243 INIT_LIST_HEAD(&work->queue); /* for list_del to work */ 244 245 spin_lock(&vcpu->async_pf.lock); 246 list_add_tail(&work->link, &vcpu->async_pf.done); 247 spin_unlock(&vcpu->async_pf.lock); 248 249 vcpu->async_pf.queued++; 250 return 0; 251 } 252