From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v4 5/6] KVM: MMU: combine guest pte read between walk and pte prefetch Date: Sun, 04 Jul 2010 17:30:59 +0300 Message-ID: <4C309B23.9060808@redhat.com> References: <4C2C9DC0.8050607@cn.fujitsu.com> <4C2C9E6C.2040803@cn.fujitsu.com> <20100702170303.GC25969@amt.cnet> <4C2F117C.2000006@cn.fujitsu.com> <4C2F2835.5060508@redhat.com> <4C2F2A0C.90704@cn.fujitsu.com> <4C2F2C5B.9020503@redhat.com> <4C2F2DBB.50904@cn.fujitsu.com> <4C2F30BD.7050702@redhat.com> <4C2F31D9.5010104@redhat.com> <4C2F3527.3020307@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Xiao Guangrong Return-path: Received: from mx1.redhat.com ([209.132.183.28]:45903 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757395Ab0GDObH (ORCPT ); Sun, 4 Jul 2010 10:31:07 -0400 In-Reply-To: <4C2F3527.3020307@cn.fujitsu.com> Sender: kvm-owner@vger.kernel.org List-ID: On 07/03/2010 04:03 PM, Xiao Guangrong wrote: > > Avi Kivity wrote: > > >>> >>> Well, in the description, it looked like everything was using small >>> pages (in kvm, level=1 means PTE level, we need to change this one >>> day). Please describe again and say exactly when the guest or host >>> uses large pages. >>> >>> >>> >> Oh, I see what you mean. >> >> Regarding the patch, is it possible just to move the check before, >> instead of adding the 'check' variable? >> >> > Umm, if we move the check before the judgment, it'll check every level, > actually, only the opened mapping and the laster level need checked, so > for the performance reason, maybe it's better to keep two check-point. > What exactly are the conditions when you want to check? Perhaps we do need to check every level. A write to a PDE (or higher level) will clear the corresponding spte, but a fault immediately afterwards can re-establish the spte to point to the new page. -- error compiling committee.c: too many arguments to function