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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * kvm asynchronous fault support4 *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 kvm_vcpu *vcpu = apf->vcpu;50 struct mm_struct *mm = vcpu->kvm->mm;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 * Attempt to pin the VM's host address space, and simply skip gup() if60 * acquiring a pin fail, i.e. if the process is exiting. Note, KVM61 * holds a reference to its associated mm_struct until the very end of62 * kvm_destroy_vm(), i.e. the struct itself won't be freed before this63 * work item is fully processed.64 */65 if (mmget_not_zero(mm)) {66 mmap_read_lock(mm);67 get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, &locked);68 if (locked)69 mmap_read_unlock(mm);70 mmput(mm);71 }72 73 /*74 * Notify and kick the vCPU even if faulting in the page failed, e.g.75 * so that the vCPU can retry the fault synchronously.76 */77 if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))78 kvm_arch_async_page_present(vcpu, apf);79 80 spin_lock(&vcpu->async_pf.lock);81 first = list_empty(&vcpu->async_pf.done);82 list_add_tail(&apf->link, &vcpu->async_pf.done);83 spin_unlock(&vcpu->async_pf.lock);84 85 /*86 * The apf struct may be freed by kvm_check_async_pf_completion() as87 * soon as the lock is dropped. Nullify it to prevent improper usage.88 */89 apf = NULL;90 91 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)92 kvm_arch_async_page_present_queued(vcpu);93 94 trace_kvm_async_pf_completed(addr, cr2_or_gpa);95 96 __kvm_vcpu_wake_up(vcpu);97}98 99static void kvm_flush_and_free_async_pf_work(struct kvm_async_pf *work)100{101 /*102 * The async #PF is "done", but KVM must wait for the work item itself,103 * i.e. async_pf_execute(), to run to completion. If KVM is a module,104 * KVM must ensure *no* code owned by the KVM (the module) can be run105 * after the last call to module_put(). Note, flushing the work item106 * is always required when the item is taken off the completion queue.107 * E.g. even if the vCPU handles the item in the "normal" path, the VM108 * could be terminated before async_pf_execute() completes.109 *110 * Wake all events skip the queue and go straight done, i.e. don't111 * need to be flushed (but sanity check that the work wasn't queued).112 */113 if (work->wakeup_all)114 WARN_ON_ONCE(work->work.func);115 else116 flush_work(&work->work);117 kmem_cache_free(async_pf_cache, work);118}119 120void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)121{122 /* cancel outstanding work queue item */123 while (!list_empty(&vcpu->async_pf.queue)) {124 struct kvm_async_pf *work =125 list_first_entry(&vcpu->async_pf.queue,126 typeof(*work), queue);127 list_del(&work->queue);128 129#ifdef CONFIG_KVM_ASYNC_PF_SYNC130 flush_work(&work->work);131#else132 if (cancel_work_sync(&work->work))133 kmem_cache_free(async_pf_cache, work);134#endif135 }136 137 spin_lock(&vcpu->async_pf.lock);138 while (!list_empty(&vcpu->async_pf.done)) {139 struct kvm_async_pf *work =140 list_first_entry(&vcpu->async_pf.done,141 typeof(*work), link);142 list_del(&work->link);143 144 spin_unlock(&vcpu->async_pf.lock);145 kvm_flush_and_free_async_pf_work(work);146 spin_lock(&vcpu->async_pf.lock);147 }148 spin_unlock(&vcpu->async_pf.lock);149 150 vcpu->async_pf.queued = 0;151}152 153void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)154{155 struct kvm_async_pf *work;156 157 while (!list_empty_careful(&vcpu->async_pf.done) &&158 kvm_arch_can_dequeue_async_page_present(vcpu)) {159 spin_lock(&vcpu->async_pf.lock);160 work = list_first_entry(&vcpu->async_pf.done, typeof(*work),161 link);162 list_del(&work->link);163 spin_unlock(&vcpu->async_pf.lock);164 165 kvm_arch_async_page_ready(vcpu, work);166 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))167 kvm_arch_async_page_present(vcpu, work);168 169 list_del(&work->queue);170 vcpu->async_pf.queued--;171 kvm_flush_and_free_async_pf_work(work);172 }173}174 175/*176 * Try to schedule a job to handle page fault asynchronously. Returns 'true' on177 * success, 'false' on failure (page fault has to be handled synchronously).178 */179bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,180 unsigned long hva, 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 false;186 187 /* Arch specific code should not do async PF in this case */188 if (unlikely(kvm_is_error_hva(hva)))189 return false;190 191 /*192 * do alloc nowait since if we are going to sleep anyway we193 * may as well sleep faulting in page194 */195 work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);196 if (!work)197 return false;198 199 work->wakeup_all = false;200 work->vcpu = vcpu;201 work->cr2_or_gpa = cr2_or_gpa;202 work->addr = hva;203 work->arch = *arch;204 205 INIT_WORK(&work->work, async_pf_execute);206 207 list_add_tail(&work->queue, &vcpu->async_pf.queue);208 vcpu->async_pf.queued++;209 work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);210 211 schedule_work(&work->work);212 213 return true;214}215 216int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)217{218 struct kvm_async_pf *work;219 bool first;220 221 if (!list_empty_careful(&vcpu->async_pf.done))222 return 0;223 224 work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);225 if (!work)226 return -ENOMEM;227 228 work->wakeup_all = true;229 INIT_LIST_HEAD(&work->queue); /* for list_del to work */230 231 spin_lock(&vcpu->async_pf.lock);232 first = list_empty(&vcpu->async_pf.done);233 list_add_tail(&work->link, &vcpu->async_pf.done);234 spin_unlock(&vcpu->async_pf.lock);235 236 if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)237 kvm_arch_async_page_present_queued(vcpu);238 239 vcpu->async_pf.queued++;240 return 0;241}242