From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 11/11] KVM: MMU: improve write flooding detected Date: Thu, 25 Aug 2011 17:06:30 +0300 Message-ID: <4E5656E6.1090204@redhat.com> References: <4E4A1257.5080204@cn.fujitsu.com> <20110823080024.GA2297@amt.cnet> <4E53872B.3070407@cn.fujitsu.com> <20110823123818.GB4261@amt.cnet> <4E53D620.9030304@cn.fujitsu.com> <20110823190939.GA10220@amt.cnet> <4E540AB4.6060905@cn.fujitsu.com> <20110824200540.GA19804@amt.cnet> <20110825020424.GA2542@amt.cnet> <4E55D2A2.7050808@redhat.com> <20110825132110.GA4384@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Xiao Guangrong , LKML , KVM To: Marcelo Tosatti Return-path: In-Reply-To: <20110825132110.GA4384@amt.cnet> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 08/25/2011 04:21 PM, Marcelo Tosatti wrote: > On Thu, Aug 25, 2011 at 07:42:10AM +0300, Avi Kivity wrote: > > On 08/25/2011 05:04 AM, Marcelo Tosatti wrote: > > >> > > >> It could increase the flood count independently of the accessed bit of > > >> the spte being updated, zapping after 3 attempts as it is now. > > >> > > >> But additionally reset the flood count if the gpte appears to be valid > > >> (points to an existant gfn if the present bit is set, or if its zeroed). > > > > > >Well not zero, as thats a common pattern for non ptes. > > > > > > > On 32-bit with 4GB RAM, practically anything is a valid gpte. > > The following could be required to consider a valid gpte, for write > flood detection purposes: > > - Must be present. > - PageCacheDisable must be unset. > - PageWriteThrough must be unset. > Unless the guest is using PAT. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.