From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() Date: Fri, 4 Mar 2016 21:48:22 +0800 Message-ID: <56D99226.8060208@linux.intel.com> References: <1457055312-27067-1-git-send-email-tianyu.lan@intel.com> <56D9417E.4000206@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Paolo Bonzini , Lan Tianyu , gleb@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org Return-path: Received: from mga01.intel.com ([192.55.52.88]:31199 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751454AbcCDNsl (ORCPT ); Fri, 4 Mar 2016 08:48:41 -0500 In-Reply-To: <56D9417E.4000206@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/04/2016 04:04 PM, Paolo Bonzini wrote: > On 04/03/2016 02:35, Lan Tianyu wrote: >> The following kvm_flush_remote_tlbs() will call smp_mb() inside and so >> remove smp_mb() here. >> >> Signed-off-by: Lan Tianyu >> --- >> arch/x86/kvm/mmu.c | 6 ------ >> 1 file changed, 6 deletions(-) >> >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c >> index a54ecd9..6315416 100644 >> --- a/arch/x86/kvm/mmu.c >> +++ b/arch/x86/kvm/mmu.c >> @@ -2383,12 +2383,6 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm, >> return; >> >> /* >> - * wmb: make sure everyone sees our modifications to the page tables >> - * rmb: make sure we see changes to vcpu->mode >> - */ >> - smp_mb(); >> - >> - /* >> * Wait for all vcpus to exit guest mode and/or lockless shadow >> * page table walks. >> */ >> > > kvm_flush_remote_tlbs loads kvm->tlbs_dirty before issuing the memory > barrier. I think it's okay if the load is done earlier, but I'd like > Guangrong to take a look. Yes, It looks good to me, but please keep the comment. Thanks!