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![Lorenzo Stoakes](/assets/img/avatar_default.png)
The only instances of get_user_pages_remote() invocations which used the vmas parameter were for a single page which can instead simply look up the VMA directly. In particular:- - __update_ref_ctr() looked up the VMA but did nothing with it so we simply remove it. - __access_remote_vm() was already using vma_lookup() when the original lookup failed so by doing the lookup directly this also de-duplicates the code. We are able to perform these VMA operations as we already hold the mmap_lock in order to be able to call get_user_pages_remote(). As part of this work we add get_user_page_vma_remote() which abstracts the VMA lookup, error handling and decrementing the page reference count should the VMA lookup fail. This forms part of a broader set of patches intended to eliminate the vmas parameter altogether. [akpm@linux-foundation.org: avoid passing NULL to PTR_ERR] Link: https://lkml.kernel.org/r/d20128c849ecdbf4dd01cc828fcec32127ed939a.1684350871.git.lstoakes@gmail.com Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> (for arm64) Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Janosch Frank <frankja@linux.ibm.com> (for s390) Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Christian König <christian.koenig@amd.com> Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jarkko Sakkinen <jarkko@kernel.org> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Sakari Ailus <sakari.ailus@linux.intel.com> Cc: Sean Christopherson <seanjc@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
227 lines
5.2 KiB
C
227 lines
5.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* kvm asynchronous fault support
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*
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* Copyright 2010 Red Hat, Inc.
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*
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* Author:
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* Gleb Natapov <gleb@redhat.com>
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*/
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#include <linux/kvm_host.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/mmu_context.h>
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#include <linux/sched/mm.h>
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#include "async_pf.h"
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#include <trace/events/kvm.h>
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static struct kmem_cache *async_pf_cache;
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int kvm_async_pf_init(void)
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{
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async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
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if (!async_pf_cache)
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return -ENOMEM;
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return 0;
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}
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void kvm_async_pf_deinit(void)
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{
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kmem_cache_destroy(async_pf_cache);
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async_pf_cache = NULL;
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}
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void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
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{
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INIT_LIST_HEAD(&vcpu->async_pf.done);
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INIT_LIST_HEAD(&vcpu->async_pf.queue);
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spin_lock_init(&vcpu->async_pf.lock);
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}
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static void async_pf_execute(struct work_struct *work)
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{
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struct kvm_async_pf *apf =
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container_of(work, struct kvm_async_pf, work);
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struct mm_struct *mm = apf->mm;
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struct kvm_vcpu *vcpu = apf->vcpu;
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unsigned long addr = apf->addr;
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gpa_t cr2_or_gpa = apf->cr2_or_gpa;
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int locked = 1;
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bool first;
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might_sleep();
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/*
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* This work is run asynchronously to the task which owns
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* mm and might be done in another context, so we must
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* access remotely.
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*/
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mmap_read_lock(mm);
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get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, &locked);
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if (locked)
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mmap_read_unlock(mm);
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if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
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kvm_arch_async_page_present(vcpu, apf);
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spin_lock(&vcpu->async_pf.lock);
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first = list_empty(&vcpu->async_pf.done);
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list_add_tail(&apf->link, &vcpu->async_pf.done);
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apf->vcpu = NULL;
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spin_unlock(&vcpu->async_pf.lock);
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if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
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kvm_arch_async_page_present_queued(vcpu);
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/*
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* apf may be freed by kvm_check_async_pf_completion() after
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* this point
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*/
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trace_kvm_async_pf_completed(addr, cr2_or_gpa);
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__kvm_vcpu_wake_up(vcpu);
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mmput(mm);
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kvm_put_kvm(vcpu->kvm);
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}
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void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
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{
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spin_lock(&vcpu->async_pf.lock);
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/* cancel outstanding work queue item */
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while (!list_empty(&vcpu->async_pf.queue)) {
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struct kvm_async_pf *work =
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list_first_entry(&vcpu->async_pf.queue,
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typeof(*work), queue);
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list_del(&work->queue);
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/*
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* We know it's present in vcpu->async_pf.done, do
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* nothing here.
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*/
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if (!work->vcpu)
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continue;
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spin_unlock(&vcpu->async_pf.lock);
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#ifdef CONFIG_KVM_ASYNC_PF_SYNC
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flush_work(&work->work);
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#else
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if (cancel_work_sync(&work->work)) {
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mmput(work->mm);
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kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
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kmem_cache_free(async_pf_cache, work);
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}
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#endif
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spin_lock(&vcpu->async_pf.lock);
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}
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while (!list_empty(&vcpu->async_pf.done)) {
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struct kvm_async_pf *work =
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list_first_entry(&vcpu->async_pf.done,
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typeof(*work), link);
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list_del(&work->link);
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kmem_cache_free(async_pf_cache, work);
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}
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spin_unlock(&vcpu->async_pf.lock);
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vcpu->async_pf.queued = 0;
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}
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void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
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{
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struct kvm_async_pf *work;
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while (!list_empty_careful(&vcpu->async_pf.done) &&
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kvm_arch_can_dequeue_async_page_present(vcpu)) {
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spin_lock(&vcpu->async_pf.lock);
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work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
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link);
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list_del(&work->link);
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spin_unlock(&vcpu->async_pf.lock);
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kvm_arch_async_page_ready(vcpu, work);
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if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
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kvm_arch_async_page_present(vcpu, work);
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list_del(&work->queue);
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vcpu->async_pf.queued--;
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kmem_cache_free(async_pf_cache, work);
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}
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}
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/*
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* Try to schedule a job to handle page fault asynchronously. Returns 'true' on
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* success, 'false' on failure (page fault has to be handled synchronously).
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*/
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bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
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unsigned long hva, struct kvm_arch_async_pf *arch)
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{
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struct kvm_async_pf *work;
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if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
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return false;
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/* Arch specific code should not do async PF in this case */
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if (unlikely(kvm_is_error_hva(hva)))
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return false;
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/*
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* do alloc nowait since if we are going to sleep anyway we
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* may as well sleep faulting in page
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*/
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work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
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if (!work)
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return false;
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work->wakeup_all = false;
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work->vcpu = vcpu;
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work->cr2_or_gpa = cr2_or_gpa;
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work->addr = hva;
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work->arch = *arch;
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work->mm = current->mm;
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mmget(work->mm);
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kvm_get_kvm(work->vcpu->kvm);
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INIT_WORK(&work->work, async_pf_execute);
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list_add_tail(&work->queue, &vcpu->async_pf.queue);
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vcpu->async_pf.queued++;
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work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);
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schedule_work(&work->work);
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return true;
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}
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int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
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{
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struct kvm_async_pf *work;
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bool first;
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if (!list_empty_careful(&vcpu->async_pf.done))
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return 0;
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work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
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if (!work)
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return -ENOMEM;
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work->wakeup_all = true;
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INIT_LIST_HEAD(&work->queue); /* for list_del to work */
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spin_lock(&vcpu->async_pf.lock);
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first = list_empty(&vcpu->async_pf.done);
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list_add_tail(&work->link, &vcpu->async_pf.done);
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spin_unlock(&vcpu->async_pf.lock);
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if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
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kvm_arch_async_page_present_queued(vcpu);
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vcpu->async_pf.queued++;
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return 0;
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}
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