Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762986AbZJOTSN (ORCPT ); Thu, 15 Oct 2009 15:18:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762977AbZJOTSM (ORCPT ); Thu, 15 Oct 2009 15:18:12 -0400 Received: from claw.goop.org ([74.207.240.146]:44170 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762976AbZJOTSJ (ORCPT ); Thu, 15 Oct 2009 15:18:09 -0400 Message-ID: <4AD7754B.20701@goop.org> Date: Thu, 15 Oct 2009 12:17:31 -0700 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-2.7.b4.fc11 Lightning/1.0pre Thunderbird/3.0b4 MIME-Version: 1.0 To: Avi Kivity CC: Dan Magenheimer , Jeremy Fitzhardinge , kurt.hackel@oracle.com, the arch/x86 maintainers , Linux Kernel Mailing List , Glauber de Oliveira Costa , Xen-devel , Keir Fraser , Zach Brown , Ingo Molnar , Chris Mason Subject: Re: [Xen-devel] Re: [PATCH 3/5] x86/pvclock: add vsyscall implementation References: <1254790211-15416-1-git-send-email-jeremy.fitzhardinge@citrix.com> <1254790211-15416-4-git-send-email-jeremy.fitzhardinge@citrix.com> <4ACB0833.2050203@redhat.com> <4ACB9074.1000804@goop.org> <4ACC6C9C.7080707@redhat.com> <4ACFD43E.6000506@goop.org> <4AD0CDFB.9030704@redhat.com> <4AD3738B.6050200@goop.org> <4AD375A5.8050205@redhat.com> <4AD37FE3.1010002@goop.org> <4AD420A4.7050508@redhat.com> <4AD4DC52.8090508@goop.org> <4AD5C4ED.3050809@redhat.com> In-Reply-To: <4AD5C4ED.3050809@redhat.com> X-Enigmail-Version: 0.97a 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: 1211 Lines: 28 On 10/14/09 05:32, Avi Kivity wrote: > On 10/14/2009 05:00 AM, Jeremy Fitzhardinge wrote: >> >>> So it's broken or disabled when that assumption is wrong? We could >>> easily fix that now. Might even reuse the pvclock structures. >>> >> Well, the kernel internally makes more or less the same assumption; the >> vsyscall clocksource is the same as the kernel's internal one. I think >> idea is that it just drops back to something like hpet if the tsc >> doesn't have very simple SMP characteristics. >> >> If the kernel could characterize the per-cpu properties of the tsc more >> accurately, then it could use the pvclock mechanism on native. >> > > It does - that's how kvm implements pvclock on the host side. See > kvmclock_cpufreq_notifier() in arch/x86/kvm/x86.c. The tsc clocksource currently seems a fair bit more picky though; it doesn't attempt to sync tscs or work out their relative offsets or rates. Which seems a bit defeatist. J -- 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/