From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: linux 3.13 guest crash with -cpu host Date: Mon, 3 Feb 2014 15:28:47 +0100 Message-ID: <20140203142847.GD3229@twins.programming.kicks-ass.net> References: <20140202205930.GA2157@redhat.com> <20140203125828.GH2221@otherpad.lan.raisama.net> <20140203140601.GA24944@redhat.com> <20140203141235.GJ8874@twins.programming.kicks-ass.net> <52EFA566.4010402@redhat.com> <20140203142642.GK8874@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Michael S. Tsirkin" , Eduardo Habkost , kvm@vger.kernel.org To: Paolo Bonzini Return-path: Received: from merlin.infradead.org ([205.233.59.134]:46616 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751412AbaBCO2u (ORCPT ); Mon, 3 Feb 2014 09:28:50 -0500 Content-Disposition: inline In-Reply-To: <20140203142642.GK8874@twins.programming.kicks-ass.net> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Feb 03, 2014 at 03:26:42PM +0100, Peter Zijlstra wrote: > On Mon, Feb 03, 2014 at 03:19:18PM +0100, Paolo Bonzini wrote: > > Il 03/02/2014 15:12, Peter Zijlstra ha scritto: > > >>> But why doesn't it crash on baremetal? > > >>> Probably baremetal simply returns 0 or something. > > >>> Let me try .. > > >The claim "v2 and above have FEATURE_PDCM" is in fact true for real > > >hardware. > > > > > >If it didn't the rdmsr() would have generated an exception and we'd have > > >crashed just like your virtual thingy did. > > > > Right, and the virt thingy has no PEBS, so there is no correct value that we > > could return from the MSR. That's why the CPUID bit is zero. > > There's more than PEBS in there, there's also the LBR format (which you > obviously also don't have) On that.. LBR is purely model based, what do you guys do with those MSRs?