From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754556Ab2GIOj0 (ORCPT ); Mon, 9 Jul 2012 10:39:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11012 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754560Ab2GIOjX (ORCPT ); Mon, 9 Jul 2012 10:39:23 -0400 Message-ID: <4FFAED16.7050204@redhat.com> Date: Mon, 09 Jul 2012 17:39:18 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Gleb Natapov , David Ahern , LKML Subject: Re: perf with precise attribute kills all KVM based VMs References: <4FFAE6D8.5050609@gmail.com> <20120709141904.GC7298@redhat.com> <1341843844.3462.75.camel@twins> In-Reply-To: <1341843844.3462.75.camel@twins> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/09/2012 05:24 PM, Peter Zijlstra wrote: > On Mon, 2012-07-09 at 17:19 +0300, Gleb Natapov wrote: >> Yes, this is knows problem that I can't find time to fix. The crash is >> cause by CPU using host PEBS virtual address while guest is running >> which causes guest memory corruption. We should disable evens that use >> PEBS at the guest entry. > > Whoops.. so the hardware is reading the DS address as programmed by the > host (host linear address) and using it as a guest linear address? > > Quality stuff.. > > Disabling PEBS events for guests isn't pretty though.. We already have atomic MSR switching at guest entry/exit time. So it's not pretty in terms of not getting full profiling, but the code won't be too hard. Basically we just have to exclude_guest any pebs event. > but I guess the > only alternative is mapping the DS into the guest and reprogramming > MSR_IA32_DS_AREA which is all a little involved I suppose? Way too involved, especially as it's virtual addresses and we don't control the guest cr3. Note that the hardware won't fail gracefully. -- error compiling committee.c: too many arguments to function