From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Huang Subject: Re: [PATCH V1 0/4] KVM vPMU support for x86 Date: Mon, 03 Nov 2014 12:47:08 -0600 Message-ID: <5457CDAC.3060408@redhat.com> References: <1414771534-29411-1-git-send-email-wei@redhat.com> <20141103175630.GA2009@potion.brq.redhat.com> <5457C83F.3050106@redhat.com> <20141103183951.GB2009@potion.brq.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm@vger.kernel.org, pbonzini@redhat.com, gleb@kernel.org To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Return-path: Received: from mx1.redhat.com ([209.132.183.28]:60396 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436AbaKCSrM (ORCPT ); Mon, 3 Nov 2014 13:47:12 -0500 In-Reply-To: <20141103183951.GB2009@potion.brq.redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 11/03/2014 12:39 PM, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote: > 2014-11-03 12:23-0600, Wei Huang: >> >> >> On 11/03/2014 11:56 AM, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote: >>> 2014-10-31 12:05-0400, Wei Huang: >>>> Currently KVM only supports vPMU for Intel platforms. This patch s= et=20 >>>> enable vPMU support for AMD platform by creating a common PMU >>>> interface for x86. The PMU calls from guest VMs are dispatched >>>> to corresponding functions defined in arch specific files. >>> >>> The functionality looks good, so I just want verify the basic desig= n: >>> why don't we emulate AMD PMU on Intel, and vice versa? >>> (Underlying PERF_COUNTs are identical in both.) >> >> Thanks. The underlining perf counters can be very different between = AMD >> and Intel. I think we can emulate AMD on Intel, or vice versa, for s= ome >> common perfmon_events (such as PERF_COUNT_HW_CPU_CYCLES). But as soo= n as >> guest VMs access raw counters (see PERF_TYPE_RAW), we can't emulate = them >> anymore. >=20 > Thanks, I guess raw counters are used more than I thought, so code > complexity would overshadow the gain of having at least something. To be honest I did try. But it became a big rat-hole as soon as I tried to abstract them. This problem also applies to Intel CPUs between generations, if perf counters are not arch_counters. -Wei >=20 > And then, there is the always perfect, "who cares" :) > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >=20