Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752958AbcCJPbV (ORCPT ); Thu, 10 Mar 2016 10:31:21 -0500 Received: from mail-wm0-f44.google.com ([74.125.82.44]:36443 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752211AbcCJPbN (ORCPT ); Thu, 10 Mar 2016 10:31:13 -0500 Subject: Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() To: Xiao Guangrong , Lan Tianyu , Thomas Gleixner References: <1457055312-27067-1-git-send-email-tianyu.lan@intel.com> <56D9354E.9040908@intel.com> <56D94BFE.1080406@redhat.com> <56DE8F1A.9000401@intel.com> <56DEEF69.20208@redhat.com> <56E1875E.8060007@linux.intel.com> <56E19224.9090906@redhat.com> Cc: gleb@kernel.org, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org From: Paolo Bonzini Message-ID: <56E1933E.20909@redhat.com> Date: Thu, 10 Mar 2016 16:31:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <56E19224.9090906@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 519 Lines: 22 On 10/03/2016 16:26, Paolo Bonzini wrote: > Compared to smp_load_acquire(), smp_mb() adds an ordering between stores > and loads. Here, the ordering is load-store, hence... > The load of kvm->tlbs_dirty should then be > > /* > * Read tlbs_dirty before setting KVM_REQ_TLB_FLUSH in > * kvm_make_all_cpus_request. This > */ > long dirty_count = smp_load_acquire(kvm->tlbs_dirty); > > Tianyu, I think Xiao provided the information that I was missing. Would > you like to prepare the patch? Thanks, Paolo