From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH 5/9] KVM: MMU: fask check write-protect for direct mmu Date: Fri, 20 Jul 2012 10:34:28 +0800 Message-ID: <5008C3B4.1070006@linux.vnet.ibm.com> References: <50056DB8.7080702@linux.vnet.ibm.com> <50056E59.4090003@linux.vnet.ibm.com> <20120720003917.GA8951@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , LKML , KVM To: Marcelo Tosatti Return-path: In-Reply-To: <20120720003917.GA8951@amt.cnet> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.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.