From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752939Ab2GTCep (ORCPT ); Thu, 19 Jul 2012 22:34:45 -0400 Received: from e23smtp06.au.ibm.com ([202.81.31.148]:45628 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752840Ab2GTCeh (ORCPT ); Thu, 19 Jul 2012 22:34:37 -0400 Message-ID: <5008C3B4.1070006@linux.vnet.ibm.com> Date: Fri, 20 Jul 2012 10:34:28 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: Marcelo Tosatti CC: Avi Kivity , LKML , KVM Subject: Re: [PATCH 5/9] KVM: MMU: fask check write-protect for direct mmu References: <50056DB8.7080702@linux.vnet.ibm.com> <50056E59.4090003@linux.vnet.ibm.com> <20120720003917.GA8951@amt.cnet> In-Reply-To: <20120720003917.GA8951@amt.cnet> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit x-cbid: 12071916-7014-0000-0000-000001955C4A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/20/2012 08:39 AM, Marcelo Tosatti wrote: > On Tue, Jul 17, 2012 at 09:53:29PM +0800, Xiao Guangrong wrote: >> If it have no indirect shadow pages we need not protect any gfn, >> this is always true for direct mmu without nested >> >> Signed-off-by: Xiao Guangrong > > Xiao, > > What is the motivation? Numbers please. > mmu_need_write_protect is the common path for both soft-mmu and hard-mmu, checking indirect_shadow_pages can skip hash-table walking for the case which is tdp is enabled without nested guest. I will post the Number after I do the performance test. > In fact, what case was the original indirect_shadow_pages conditional in > kvm_mmu_pte_write optimizing again? > They are the different paths, mmu_need_write_protect is the real page fault path, and kvm_mmu_pte_write is caused by mmio emulation.