Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759240Ab0FVJrI (ORCPT ); Tue, 22 Jun 2010 05:47:08 -0400 Received: from casper.infradead.org ([85.118.1.10]:33901 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759192Ab0FVJrF convert rfc822-to-8bit (ORCPT ); Tue, 22 Jun 2010 05:47:05 -0400 Subject: Re: [PATCH V2 1/5] ara virt interface of perf to support kvm guest os statistics collection in guest os From: Peter Zijlstra To: Jes Sorensen Cc: "Zhang, Yanmin" , Avi Kivity , LKML , kvm@vger.kernel.org, Ingo Molnar , Fr??d??ric Weisbecker , Arnaldo Carvalho de Melo , Cyrill Gorcunov , Lin Ming , Sheng Yang , Marcelo Tosatti , oerg Roedel , Gleb Natapov , Zachary Amsden , zhiteng.huang@intel.com, tim.c.chen@intel.com In-Reply-To: <4C2084BB.3040501@redhat.com> References: <1277112680.2096.509.camel@ymzhang.sh.intel.com> <4C1F50D0.70205@redhat.com> <1277171344.2096.567.camel@ymzhang.sh.intel.com> <4C2062D8.20609@redhat.com> <1277192873.2096.690.camel@ymzhang.sh.intel.com> <1277193305.1875.537.camel@laptop> <4C206D8B.4080105@redhat.com> <1277198943.2096.724.camel@ymzhang.sh.intel.com> <1277199060.1875.675.camel@laptop> <4C2084BB.3040501@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Tue, 22 Jun 2010 11:46:50 +0200 Message-ID: <1277200010.1875.692.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1701 Lines: 35 On Tue, 2010-06-22 at 11:39 +0200, Jes Sorensen wrote: > On 06/22/10 11:31, Peter Zijlstra wrote: > > On Tue, 2010-06-22 at 17:29 +0800, Zhang, Yanmin wrote: > >> On Tue, 2010-06-22 at 10:00 +0200, Jes Sorensen wrote: > >>> On 06/22/10 09:55, Peter Zijlstra wrote: > >>>> On Tue, 2010-06-22 at 15:47 +0800, Zhang, Yanmin wrote: > >>>>> Besides the para virt perf interface, I'm also considering the direct exposition > >>>>> of PMU hardware to guest os. > >>>> > >>>> NAK NAK NAK NAK, we've been over that, its not going to happen, full > >>>> stop! > >>>> > >>>> Use MSR read/write traps and host perf to emulate the hardware. In some > >>>> cases we could allow the reads without trap but that's a later > >>>> optimization. > >>> > >>> I believe whats meant here is a PMU compatible interface which is > >>> partially emulated. Not a handover of the PMU. > >> Right. We need capture all write to PMU MSR and allows guest os to read MSR directly. > > > > That latter is not possible, only in a subset of cases can you allow > > that read. > > Avi's suggestion of using virtual MSRs makes a ton of sense for this > though, and it makes it possible to switch direct access on/off for the > cases where direct access is possible, and go emulated when it isn't. /me has no clue what virtual MSRs are, but yeah, that sounds about right. Anyway, the generic case is full trap and emulate get that working first, then try and be smart and avoid some traps. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/