From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH v2 0/2] kvm: x86: Emulate MSR_PLATFORM_INFO Date: Tue, 18 Jun 2013 18:16:52 +0300 Message-ID: <20130618151652.GA21032@redhat.com> References: <1370361738-4277-1-git-send-email-bsd@redhat.com> <20130605084213.GQ4725@redhat.com> <51C06914.1090904@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Bandan Das , kvm@vger.kernel.org, Marcelo Tosatti , "Nakajima, Jun" To: Paolo Bonzini Return-path: Received: from mx1.redhat.com ([209.132.183.28]:45148 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755921Ab3FRPQ5 (ORCPT ); Tue, 18 Jun 2013 11:16:57 -0400 Content-Disposition: inline In-Reply-To: <51C06914.1090904@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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. -- Gleb.