From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] KVM: VMX: Update instruction length on intercepted BP Date: Wed, 17 Feb 2010 13:13:27 +0200 Message-ID: <20100217111327.GR2995@redhat.com> References: <4B77E0E2.7030704@web.de> <20100214144501.GN2511@redhat.com> <4B7826D3.7080201@web.de> <20100214165319.GA19246@redhat.com> <4B782D97.9030304@web.de> <20100214172613.GB19246@redhat.com> <4B7837A3.4040607@web.de> <4B794A1F.7050009@siemens.com> <20100215133042.GC19478@redhat.com> <4B7BCEE8.8040708@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kiszka , Marcelo Tosatti , kvm To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:37104 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751000Ab0BQLNh (ORCPT ); Wed, 17 Feb 2010 06:13:37 -0500 Content-Disposition: inline In-Reply-To: <4B7BCEE8.8040708@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Feb 17, 2010 at 01:11:36PM +0200, Avi Kivity wrote: > On 02/15/2010 03:30 PM, Gleb Natapov wrote: > > > >>I just did this on our primary AMD platform (Embedded Opteron, 13KS EE), > >>and it just worked. > >> > >>But this is a fairly new processor. Consequently, it reports NextRIP > >>support via cpuid function 0x8000000A. Looking for an older one too. > >> > >>In the meantime I also browsed a bit more in the manuals, and I don't > >>think stepping over or (what is actually required) into an INT3 will > >>work. We can't step into as the processor clears TF on any event handler > >>entry. And stepping over would cause troubles > >> > >>a) as an unknown amount of code may run without #DB interception > >>b) we would fiddle with TF in code that is already under debugger > >> control, thus we would very likely run into conflicts. > >> > >>Leaves us with tricky INT3 emulation. Sigh. > >> > >So the question is do we want to support this kind of debugging on older > >AMDs. May we don't. > > How much older are they? > Actually I am not sure new AMDs support this correctly. Need one to run tests. GDB is not a good test case, it is too smart. -- Gleb.