From patchwork Tue Feb 18 08:22:47 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Takuya Yoshikawa X-Patchwork-Id: 3667451 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id B72F99F1EE for ; Tue, 18 Feb 2014 08:24:37 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id C3179201FD for ; Tue, 18 Feb 2014 08:24:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5B90201F7 for ; Tue, 18 Feb 2014 08:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754612AbaBRIYc (ORCPT ); Tue, 18 Feb 2014 03:24:32 -0500 Received: from tama500.ecl.ntt.co.jp ([129.60.39.148]:50166 "EHLO tama500.ecl.ntt.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754193AbaBRIYb (ORCPT ); Tue, 18 Feb 2014 03:24:31 -0500 Received: from mfs5.rdh.ecl.ntt.co.jp (mfs5.rdh.ecl.ntt.co.jp [129.60.39.144]) by tama500.ecl.ntt.co.jp (8.13.8/8.13.8) with ESMTP id s1I8I4fw004577; Tue, 18 Feb 2014 17:18:04 +0900 Received: from mfs5.rdh.ecl.ntt.co.jp (localhost.localdomain [127.0.0.1]) by mfs5.rdh.ecl.ntt.co.jp (Postfix) with ESMTP id D9511E013A; Tue, 18 Feb 2014 17:18:04 +0900 (JST) Received: from imail2.m.ecl.ntt.co.jp (imail2.m.ecl.ntt.co.jp [129.60.5.247]) by mfs5.rdh.ecl.ntt.co.jp (Postfix) with ESMTP id CD7E9E0138; Tue, 18 Feb 2014 17:18:04 +0900 (JST) Received: from yshpad ([129.60.241.228]) by imail2.m.ecl.ntt.co.jp (8.13.8/8.13.8) with SMTP id s1I8I4E0015179; Tue, 18 Feb 2014 17:18:04 +0900 Date: Tue, 18 Feb 2014 17:22:47 +0900 From: Takuya Yoshikawa To: gleb@kernel.org, pbonzini@redhat.com Cc: kvm@vger.kernel.org Subject: [PATCH A] KVM: Simplify kvm->tlbs_dirty handling Message-Id: <20140218172247.ca61f503.yoshikawa_takuya_b1@lab.ntt.co.jp> In-Reply-To: <20140218172150.7723d3a5.yoshikawa_takuya_b1@lab.ntt.co.jp> References: <20140218172150.7723d3a5.yoshikawa_takuya_b1@lab.ntt.co.jp> X-Mailer: Sylpheed 3.1.0 (GTK+ 2.24.4; x86_64-pc-linux-gnu) Mime-Version: 1.0 X-TM-AS-MML: No Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When this was introduced, kvm_flush_remote_tlbs() could be called without holding mmu_lock. It is now acknowledged that the function must be called before releasing mmu_lock, and all callers have already been changed to do so. There is no need to use smp_mb() and cmpxchg() any more. Signed-off-by: Takuya Yoshikawa --- arch/x86/kvm/paging_tmpl.h | 7 ++++--- include/linux/kvm_host.h | 2 +- virt/kvm/kvm_main.c | 11 +++++++---- 3 files changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index cba218a..b1e6c1b 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -913,7 +913,8 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr, * and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't * used by guest then tlbs are not flushed, so guest is allowed to access the * freed pages. - * And we increase kvm->tlbs_dirty to delay tlbs flush in this case. + * We set tlbs_dirty to let the notifier know this change and delay the flush + * until such a case actually happens. */ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { @@ -942,7 +943,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) return -EINVAL; if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) { - vcpu->kvm->tlbs_dirty++; + vcpu->kvm->tlbs_dirty = true; continue; } @@ -957,7 +958,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) if (gfn != sp->gfns[i]) { drop_spte(vcpu->kvm, &sp->spt[i]); - vcpu->kvm->tlbs_dirty++; + vcpu->kvm->tlbs_dirty = true; continue; } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index f5937b8..ed1cc89 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -401,7 +401,7 @@ struct kvm { unsigned long mmu_notifier_seq; long mmu_notifier_count; #endif - long tlbs_dirty; + bool tlbs_dirty; struct list_head devices; }; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a9e999a..51744da 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -186,12 +186,15 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) void kvm_flush_remote_tlbs(struct kvm *kvm) { - long dirty_count = kvm->tlbs_dirty; - - smp_mb(); if (make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH)) ++kvm->stat.remote_tlb_flush; - cmpxchg(&kvm->tlbs_dirty, dirty_count, 0); + /* + * tlbs_dirty is used only for optimizing x86's shadow paging code with + * mmu notifiers in mind, see the note on sync_page(). Since it is + * always protected with mmu_lock there, should kvm_flush_remote_tlbs() + * be called before releasing mmu_lock, this is safe. + */ + kvm->tlbs_dirty = false; } EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);