From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v3 07/15] KVM: MMU: introduce nulls desc Date: Mon, 25 Nov 2013 18:25:10 +0800 Message-ID: <52932586.2010301@linux.vnet.ibm.com> References: <1382534973-13197-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <1382534973-13197-8-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20131122191429.GA13308@amt.cnet> <65EE805B-B5DB-4BD0-A057-E5FF78D96D67@linux.vnet.ibm.com> <20131125101943.GS2108@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Marcelo Tosatti , avi.kivity@gmail.com, "pbonzini@redhat.com Bonzini" , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Eric Dumazet , Peter Zijlstra To: Gleb Natapov Return-path: In-Reply-To: <20131125101943.GS2108@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 11/25/2013 06:19 PM, Gleb Natapov wrote: > On Mon, Nov 25, 2013 at 02:11:31PM +0800, Xiao Guangrong wrote: >>> >>> For example, nothing prevents lockless walker to move into some >>> parent_ptes chain, right? >> >> No. >> >> The nulls can help us to detect this case, for parent_ptes, the null= s points >> to "shadow page" but for rmaps, the nulls points to slot.arch.rmap. = There >> is no chance that the =EF=BF=BDrmap" is used as shadow page when slo= t-lock is held. >> > But meanwhile we will write protect non-last level sptes, no? Better = to It will meet the non-last sptes but does not write-protect them since we have do is_last_spte() check before cmpxchg. > create separate slab caches for rmap and parent_ptes lists. Yes, this is a good idea. Thanks you, Gleb!