From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Roedel, Joerg" Subject: Re: [PATCH] KVM: SVM: Keep intercepting task switching with NPT enabled Date: Wed, 19 Oct 2011 16:12:11 +0200 Message-ID: <20111019141211.GP2198@amd.com> References: <4E9DA7EF.30804@siemens.com> <20111018163516.GO2198@amd.com> <4E9DB95C.1030105@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Jan Kiszka , Marcelo Tosatti , kvm , Gleb Natapov To: Avi Kivity Return-path: Received: from tx2ehsobe004.messaging.microsoft.com ([65.55.88.14]:32914 "EHLO TX2EHSOBE007.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440Ab1JSOMV (ORCPT ); Wed, 19 Oct 2011 10:12:21 -0400 Content-Disposition: inline In-Reply-To: <4E9DB95C.1030105@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Oct 18, 2011 at 01:37:32PM -0400, Avi Kivity wrote: > On 10/18/2011 06:35 PM, Roedel, Joerg wrote: > > On Tue, Oct 18, 2011 at 12:23:11PM -0400, Jan Kiszka wrote: > > > AMD processors apparently have a bug in the hardware task switching > > > support when NPT is enabled. If the task switch triggers a NPF, we can > > > get wrong EXITINTINFO along with that fault. On resume, spurious > > > exceptions may then be injected into the guest. > > > > > > We were able to reproduce this bug when our guest triggered #SS and the > > > handler were supposed to run over a separate task with not yet touched > > > stack pages. > > > > > > Work around the issue by continuing to emulate task switches even in > > > NPT mode. > > > > > > Signed-off-by: Jan Kiszka > > > > Acked-by: Joerg Roedel > > > > Will there be an erratum published for this bug? Are all processors > affected? For now this behavior should be expected on all NPT capable processors. > I'd like to limit this to just the buggy processors, if and when fixed > processors become available. I don't know this yet, but I'll try to find out. Thanks, Joerg -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo, Andrew Bowd Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632