// SPDX-License-Identifier: GPL-2.0-only /* * kvm asynchronous fault support * * Copyright 2010 Red Hat, Inc. * * Author: * Gleb Natapov <gleb@redhat.com> */ #include <linux/kvm_host.h> #include <linux/slab.h> #include <linux/module.h> #include <linux/mmu_context.h> #include <linux/sched/mm.h> #include "async_pf.h" #include <trace/events/kvm.h> static struct kmem_cache *async_pf_cache; int kvm_async_pf_init(void) { async_pf_cache = KMEM_CACHE(kvm_async_pf, 0); if (!async_pf_cache) return -ENOMEM; return 0; } void kvm_async_pf_deinit(void) { kmem_cache_destroy(async_pf_cache); async_pf_cache = NULL; } void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu) { INIT_LIST_HEAD(&vcpu->async_pf.done); INIT_LIST_HEAD(&vcpu->async_pf.queue); spin_lock_init(&vcpu->async_pf.lock); } static void async_pf_execute(struct work_struct *work) { struct kvm_async_pf *apf = container_of(work, struct kvm_async_pf, work); struct mm_struct *mm = apf->mm; struct kvm_vcpu *vcpu = apf->vcpu; unsigned long addr = apf->addr; gpa_t cr2_or_gpa = apf->cr2_or_gpa; int locked = 1; bool first; might_sleep(); /* * This work is run asynchronously to the task which owns * mm and might be done in another context, so we must * access remotely. */ mmap_read_lock(mm); get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, &locked); if (locked) mmap_read_unlock(mm); if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC)) kvm_arch_async_page_present(vcpu, apf); spin_lock(&vcpu->async_pf.lock); first = list_empty(&vcpu->async_pf.done); list_add_tail(&apf->link, &vcpu->async_pf.done); apf->vcpu = NULL; spin_unlock(&vcpu->async_pf.lock); if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first) kvm_arch_async_page_present_queued(vcpu); /* * apf may be freed by kvm_check_async_pf_completion() after * this point */ trace_kvm_async_pf_completed(addr, cr2_or_gpa); __kvm_vcpu_wake_up(vcpu); mmput(mm); kvm_put_kvm(vcpu->kvm); } void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) { spin_lock(&vcpu->async_pf.lock); /* cancel outstanding work queue item */ while (!list_empty(&vcpu->async_pf.queue)) { struct kvm_async_pf *work = list_first_entry(&vcpu->async_pf.queue, typeof(*work), queue); list_del(&work->queue); /* * We know it's present in vcpu->async_pf.done, do * nothing here. */ if (!work->vcpu) continue; spin_unlock(&vcpu->async_pf.lock); #ifdef CONFIG_KVM_ASYNC_PF_SYNC flush_work(&work->work); #else if (cancel_work_sync(&work->work)) { mmput(work->mm); kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */ kmem_cache_free(async_pf_cache, work); } #endif spin_lock(&vcpu->async_pf.lock); } while (!list_empty(&vcpu->async_pf.done)) { struct kvm_async_pf *work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link); list_del(&work->link); kmem_cache_free(async_pf_cache, work); } spin_unlock(&vcpu->async_pf.lock); vcpu->async_pf.queued = 0; } void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) { struct kvm_async_pf *work; while (!list_empty_careful(&vcpu->async_pf.done) && kvm_arch_can_dequeue_async_page_present(vcpu)) { spin_lock(&vcpu->async_pf.lock); work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link); list_del(&work->link); spin_unlock(&vcpu->async_pf.lock); kvm_arch_async_page_ready(vcpu, work); if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC)) kvm_arch_async_page_present(vcpu, work); list_del(&work->queue); vcpu->async_pf.queued--; kmem_cache_free(async_pf_cache, work); } } /* * Try to schedule a job to handle page fault asynchronously. Returns 'true' on * success, 'false' on failure (page fault has to be handled synchronously). */ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, unsigned long hva, struct kvm_arch_async_pf *arch) { struct kvm_async_pf *work; if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU) return false; /* Arch specific code should not do async PF in this case */ if (unlikely(kvm_is_error_hva(hva))) return false; /* * do alloc nowait since if we are going to sleep anyway we * may as well sleep faulting in page */ work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN); if (!work) return false; work->wakeup_all = false; work->vcpu = vcpu; work->cr2_or_gpa = cr2_or_gpa; work->addr = hva; work->arch = *arch; work->mm = current->mm; mmget(work->mm); kvm_get_kvm(work->vcpu->kvm); INIT_WORK(&work->work, async_pf_execute); list_add_tail(&work->queue, &vcpu->async_pf.queue); vcpu->async_pf.queued++; work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work); schedule_work(&work->work); return true; } int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu) { struct kvm_async_pf *work; bool first; if (!list_empty_careful(&vcpu->async_pf.done)) return 0; work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC); if (!work) return -ENOMEM; work->wakeup_all = true; INIT_LIST_HEAD(&work->queue); /* for list_del to work */ spin_lock(&vcpu->async_pf.lock); first = list_empty(&vcpu->async_pf.done); list_add_tail(&work->link, &vcpu->async_pf.done); spin_unlock(&vcpu->async_pf.lock); if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first) kvm_arch_async_page_present_queued(vcpu); vcpu->async_pf.queued++; return 0; }