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 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 } 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 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 47 void kvm_async_pf_deinit(void) 48 { 49 kmem_cache_destroy(async_pf_cache); 50 async_pf_cache = NULL; 51 } 52 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 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 } 103 104 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 } 146 147 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 } 167 168 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 } 214 215 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