From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bandan Das Subject: Re: [PATCH v2 0/2] kvm: x86: Emulate MSR_PLATFORM_INFO Date: Tue, 18 Jun 2013 11:29:27 -0400 Message-ID: References: <1370361738-4277-1-git-send-email-bsd@redhat.com> <20130605084213.GQ4725@redhat.com> <51C06914.1090904@redhat.com> <20130618151652.GA21032@redhat.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Paolo Bonzini , kvm@vger.kernel.org, Marcelo Tosatti , "Nakajima\, Jun" To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:23372 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932302Ab3FRP33 (ORCPT ); Tue, 18 Jun 2013 11:29:29 -0400 In-Reply-To: <20130618151652.GA21032@redhat.com> (Gleb Natapov's message of "Tue, 18 Jun 2013 18:16:52 +0300") Sender: kvm-owner@vger.kernel.org List-ID: Gleb Natapov writes: > On Tue, Jun 18, 2013 at 04:05:08PM +0200, Paolo Bonzini wrote: >> Il 05/06/2013 10:42, Gleb Natapov ha scritto: >> >> > These patches add an emulated MSR_PLATFORM_INFO that kvm guests >> >> > can read as described in section 14.3.2.4 of the Intel SDM. >> >> > The relevant changes and details are in [2/2]; [1/2] makes vendor_intel >> >> > generic. There are atleat two known applications that fail to run because >> >> > of this MSR missing - Sandra and vTune. >> > So I really want Intel opinion on this. Right now it is impossible to >> > implement the MSR correctly in the face of migration (may be with tsc >> > scaling it will be possible) and while it is unimplemented if application >> > tries to use it it fails, but if we will implement it application will >> > just produce incorrect result without any means for user to detect it. >> >> Jun, ping? (Perhaps Gleb you want to ask a more specific question though). >> >> I don't think this is much different from any other RDTSC usage in >> applications (they will typically do their calibration manually, and do >> it just once). I'm applying it to queue. >> > And we do not support application that uses RDTSC directly! If we could > catch those it would be good from support point of view, so the way > MSR_PLATFORM_INFO behaves now it better then proposed alternative. If support is the issue, can't we have a flag that disables this by default and users who want to take the plunge (and be responsible for the consequences) can enable it to read platform_info ? > -- > Gleb.