From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH] KVM: SVM: fix random segfaults with NPT enabled Date: Wed, 27 Aug 2008 17:32:25 +0200 Message-ID: <20080827153225.GA3801@8bytes.org> References: <1219839523-25677-1-git-send-email-joerg.roedel@amd.com> <48B55266.4000300@qumranet.com> <20080827135326.GB26059@amd.com> <48B57104.7060001@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Joerg Rodel , kvm@vger.kernel.org, stable@kernel.org, Alexander Graf To: Avi Kivity Return-path: Received: from 8bytes.org ([88.198.83.132]:44396 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753670AbYH0P6T (ORCPT ); Wed, 27 Aug 2008 11:58:19 -0400 Content-Disposition: inline In-Reply-To: <48B57104.7060001@qumranet.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Aug 27, 2008 at 06:21:40PM +0300, Avi Kivity wrote: > Joerg Rodel wrote: > > > > >>hm. tbench doesn't allocate memory, so there shouldn't be any npt > >>faults. I don't see how this can make a difference. > >> > > > > > > I reproduced it. There are a few npt faults as the guest has not > touched all of memory yet. If I force it to touch all of memory (dd < > /dev/hda), the problem appears to go away. > > >Base for the fix was this bugreport: > > > >http://sourceforge.net/tracker/index.php?func=detail&aid=2019053&group_id=180599&atid=893831 > > > >We found out that the same crash occur on long running compile > >workloads and that stale tlb-entries cause it. Until we find the real > >location of the missing tlb flush in the mmu code, i think its best to > >flush the TLB every time the mapping/unmapping code for the nested page > >table is executed. This fixes at least the crashes in the guest and has > >only minimal performance impact. > > > > I'd like to try and find out what the problem is exactly. Otherwise we > may be only narrowing the window, not closing it. Agreed. The fix I sent is only meant to be temporary until we find the real root cause of the problem. Joerg