Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759150Ab0FVJjo (ORCPT ); Tue, 22 Jun 2010 05:39:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:24238 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754974Ab0FVJjm (ORCPT ); Tue, 22 Jun 2010 05:39:42 -0400 Message-ID: <4C2084BB.3040501@redhat.com> Date: Tue, 22 Jun 2010 11:39:07 +0200 From: Jes Sorensen User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Lightning/1.0b2pre Thunderbird/3.0.4 MIME-Version: 1.0 To: Peter Zijlstra 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 Subject: Re: [PATCH V2 1/5] ara virt interface of perf to support kvm guest os statistics collection in guest os 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> In-Reply-To: <1277199060.1875.675.camel@laptop> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1417 Lines: 34 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. Cheers, Jes -- 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/