From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock Date: Mon, 19 Apr 2010 13:54:12 +0300 Message-ID: <4BCC3654.2090600@redhat.com> References: <1271356648-5108-1-git-send-email-glommer@redhat.com> <1271356648-5108-2-git-send-email-glommer@redhat.com> <4BCA026D.3070309@redhat.com> <1271673975.1674.763.camel@laptop> <4BCC3520.6090305@redhat.com> <1271674273.1674.777.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jeremy Fitzhardinge , Marcelo Tosatti , Zachary Amsden To: Peter Zijlstra Return-path: Received: from mx1.redhat.com ([209.132.183.28]:1027 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754100Ab0DSKyP (ORCPT ); Mon, 19 Apr 2010 06:54:15 -0400 In-Reply-To: <1271674273.1674.777.camel@laptop> Sender: kvm-owner@vger.kernel.org List-ID: On 04/19/2010 01:51 PM, Peter Zijlstra wrote: > > >>> Right, so on x86 we have: >>> >>> X86_FEATURE_CONSTANT_TSC, which only states that TSC is frequency >>> independent, not that it doesn't stop in C states and similar fun stuff. >>> >>> X86_FEATURE_TSC_RELIABLE, which IIRC should indicate the TSC is constant >>> and synced between cores. >>> >>> >>> >> Sockets and boards too? (IOW, how reliable is TSC_RELIABLE)? >> > Not sure, IIRC we clear that when the TSC sync test fails, eg when we > mark the tsc clocksource unusable. > Worrying. By the time we detect this the guest may already have gotten confused by clocks going backwards. -- error compiling committee.c: too many arguments to function