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 20static struct kmem_cache *async_pf_cache; 21 22int kvm_async_pf_init(void) 23{ 24 async_pf_cache = KMEM_CACHE(kvm_async_pf, 0); 25 26 if (!async_pf_cache) 27 return -ENOMEM; 28 29 return 0; 30} 31 32void kvm_async_pf_deinit(void) 33{ 34 kmem_cache_destroy(async_pf_cache); 35 async_pf_cache = NULL; 36} 37 38void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu) 39{ 40 INIT_LIST_HEAD(&vcpu->async_pf.done); 41 INIT_LIST_HEAD(&vcpu->async_pf.queue); 42 spin_lock_init(&vcpu->async_pf.lock); 43} 44 45static void async_pf_execute(struct work_struct *work) 46{ 47 struct kvm_async_pf *apf = 48 container_of(work, struct kvm_async_pf, work); 49 struct mm_struct *mm = apf->mm; 50 struct kvm_vcpu *vcpu = apf->vcpu; 51 unsigned long addr = apf->addr; 52 gpa_t cr2_or_gpa = apf->cr2_or_gpa; 53 int locked = 1; 54 bool first; 55 56 might_sleep(); 57 58 /* 59 * This work is run asynchronously to the task which owns 60 * mm and might be done in another context, so we must 61 * access remotely. 62 */ 63 mmap_read_lock(mm); 64 get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, &locked); 65 if (locked) 66 mmap_read_unlock(mm); 67 68 if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC)) 69 kvm_arch_async_page_present(vcpu, apf); 70 71 spin_lock(&vcpu->async_pf.lock); 72 first = list_empty(&vcpu->async_pf.done); 73 list_add_tail(&apf->link, &vcpu->async_pf.done); 74 apf->vcpu = NULL; 75 spin_unlock(&vcpu->async_pf.lock); 76 77 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first) 78 kvm_arch_async_page_present_queued(vcpu); 79 80 /* 81 * apf may be freed by kvm_check_async_pf_completion() after 82 * this point 83 */ 84 85 trace_kvm_async_pf_completed(addr, cr2_or_gpa); 86 87 __kvm_vcpu_wake_up(vcpu); 88 89 mmput(mm); 90} 91 92static void kvm_flush_and_free_async_pf_work(struct kvm_async_pf *work) 93{ 94 /* 95 * The async #PF is "done", but KVM must wait for the work item itself, 96 * i.e. async_pf_execute(), to run to completion. If KVM is a module, 97 * KVM must ensure *no* code owned by the KVM (the module) can be run 98 * after the last call to module_put(). Note, flushing the work item 99 * is always required when the item is taken off the completion queue. 100 * E.g. even if the vCPU handles the item in the "normal" path, the VM 101 * could be terminated before async_pf_execute() completes. 102 * 103 * Wake all events skip the queue and go straight done, i.e. don't 104 * need to be flushed (but sanity check that the work wasn't queued). 105 */ 106 if (work->wakeup_all) 107 WARN_ON_ONCE(work->work.func); 108 else 109 flush_work(&work->work); 110 kmem_cache_free(async_pf_cache, work); 111} 112 113void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) 114{ 115 spin_lock(&vcpu->async_pf.lock); 116 117 /* cancel outstanding work queue item */ 118 while (!list_empty(&vcpu->async_pf.queue)) { 119 struct kvm_async_pf *work = 120 list_first_entry(&vcpu->async_pf.queue, 121 typeof(*work), queue); 122 list_del(&work->queue); 123 124 /* 125 * We know it's present in vcpu->async_pf.done, do 126 * nothing here. 127 */ 128 if (!work->vcpu) 129 continue; 130 131 spin_unlock(&vcpu->async_pf.lock); 132#ifdef CONFIG_KVM_ASYNC_PF_SYNC 133 flush_work(&work->work); 134#else 135 if (cancel_work_sync(&work->work)) { 136 mmput(work->mm); 137 kmem_cache_free(async_pf_cache, work); 138 } 139#endif 140 spin_lock(&vcpu->async_pf.lock); 141 } 142 143 while (!list_empty(&vcpu->async_pf.done)) { 144 struct kvm_async_pf *work = 145 list_first_entry(&vcpu->async_pf.done, 146 typeof(*work), link); 147 list_del(&work->link); 148 149 spin_unlock(&vcpu->async_pf.lock); 150 kvm_flush_and_free_async_pf_work(work); 151 spin_lock(&vcpu->async_pf.lock); 152 } 153 spin_unlock(&vcpu->async_pf.lock); 154 155 vcpu->async_pf.queued = 0; 156} 157 158void 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_dequeue_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 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC)) 172 kvm_arch_async_page_present(vcpu, work); 173 174 list_del(&work->queue); 175 vcpu->async_pf.queued--; 176 kvm_flush_and_free_async_pf_work(work); 177 } 178} 179 180/* 181 * Try to schedule a job to handle page fault asynchronously. Returns 'true' on 182 * success, 'false' on failure (page fault has to be handled synchronously). 183 */ 184bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, 185 unsigned long hva, 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 false; 191 192 /* Arch specific code should not do async PF in this case */ 193 if (unlikely(kvm_is_error_hva(hva))) 194 return false; 195 196 /* 197 * do alloc nowait since if we are going to sleep anyway we 198 * may as well sleep faulting in page 199 */ 200 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN); 201 if (!work) 202 return false; 203 204 work->wakeup_all = false; 205 work->vcpu = vcpu; 206 work->cr2_or_gpa = cr2_or_gpa; 207 work->addr = hva; 208 work->arch = *arch; 209 work->mm = current->mm; 210 mmget(work->mm); 211 212 INIT_WORK(&work->work, async_pf_execute); 213 214 list_add_tail(&work->queue, &vcpu->async_pf.queue); 215 vcpu->async_pf.queued++; 216 work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work); 217 218 schedule_work(&work->work); 219 220 return true; 221} 222 223int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu) 224{ 225 struct kvm_async_pf *work; 226 bool first; 227 228 if (!list_empty_careful(&vcpu->async_pf.done)) 229 return 0; 230 231 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC); 232 if (!work) 233 return -ENOMEM; 234 235 work->wakeup_all = true; 236 INIT_LIST_HEAD(&work->queue); /* for list_del to work */ 237 238 spin_lock(&vcpu->async_pf.lock); 239 first = list_empty(&vcpu->async_pf.done); 240 list_add_tail(&work->link, &vcpu->async_pf.done); 241 spin_unlock(&vcpu->async_pf.lock); 242 243 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first) 244 kvm_arch_async_page_present_queued(vcpu); 245 246 vcpu->async_pf.queued++; 247 return 0; 248} 249