From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: cr3 OOS optimisation breaks 32-bit GNU/kFreeBSD guest Date: Sun, 05 Apr 2009 14:41:02 +0300 Message-ID: <49D898CE.2050308@redhat.com> References: <20090223003305.GW12976@hall.aurel32.net> <20090320231405.GA26415@amt.cnet> <49C60644.2090904@redhat.com> <20090323172725.GA28775@amt.cnet> <49C8AC35.3030803@redhat.com> <20090403214548.GA5394@amt.cnet> <49D73873.2090302@redhat.com> <20090404170143.GA3303@amt.cnet> <49D86EC3.3070902@redhat.com> <20090405112917.GA4105@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Aurelien Jarno , kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mx2.redhat.com ([66.187.237.31]:36962 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751745AbZDELlK (ORCPT ); Sun, 5 Apr 2009 07:41:10 -0400 In-Reply-To: <20090405112917.GA4105@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: Marcelo Tosatti wrote: >> Here's one way to make this work: >> >> - add a hash of global pagetables, indexed by virtual address instead >> of the pagetable's gfn >> - invlpg checks this hash in addition to the recursive walk >> >> We'd need to make the virtual address part of sp->role to avoid needing >> to link the same page multiple times in the virtual address hash. >> > > Humpf, yes. It seems its too expensive/complex to handle this, for such > small gain (~= 2% on AIM7 with RHEL3 guest). > > Are you okay with just disabling the global pages optimization? > Definitely to plug the hole; and probably for later as well, unless people cry out due to regressions. Please send it in two patches: one a trivial one to disable global page detection which can be sent to -stable as well, and a follow on which rips out the global page machinery until (and if) we decide to reimplement it correctly. -- error compiling committee.c: too many arguments to function