From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756307Ab0ERQpI (ORCPT ); Tue, 18 May 2010 12:45:08 -0400 Received: from terminus.zytor.com ([198.137.202.10]:52420 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754213Ab0ERQpD (ORCPT ); Tue, 18 May 2010 12:45:03 -0400 Message-ID: <4BF2C30F.6030502@zytor.com> Date: Tue, 18 May 2010 09:40:47 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Peter Zijlstra CC: Andi Kleen , Arjan van de Ven , Dan Magenheimer , Thomas Gleixner , Venkatesh Pallipadi , Ingo Molnar , chris.mason@oracle.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: Export tsc related information in sysfs References: <1273887635-27610-1-git-send-email-venki@google.com> <87tyq9mqrz.fsf@basil.nowhere.org> <35aa841b-e151-424d-b1c1-0c03dbcae5cc@default> <20100515121424.38f5b389@infradead.org> <20100515224305.17a04022@infradead.org> <5adf3fee-0f7b-4039-b13f-619640cc4b88@default> <20100516220638.2baf315d@infradead.org> <1274176698.5605.7358.camel@twins> <20100518112509.GD22675@basil.fritz.box> <1274183935.5605.7726.camel@twins> In-Reply-To: <1274183935.5605.7726.camel@twins> 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 On 05/18/2010 04:58 AM, Peter Zijlstra wrote: > On Tue, 2010-05-18 at 13:25 +0200, Andi Kleen wrote: >> On Tue, May 18, 2010 at 11:58:18AM +0200, Peter Zijlstra wrote: >>> On Sun, 2010-05-16 at 22:06 -0700, Arjan van de Ven wrote: >>>> look we're not disabling ring 3 tsc. We could, but we don't. >>> >>> Maybe we should. >> >> That would kill the vsyscall too. Remember it's running in ring 3. >> >> That is in theory you could disable it on systems where the vsyscall >> doesn't use it, but then you would likely break huge amounts of software, >> unless you emulate it. > > Well, software shouldn't use it, so breaking it sounds like a fine > idea ;-) > > Also, a slow emulation is an incentive to actually do the right thing. The problem is that you throw the baby (vsyscall) out with the bathwater (user rdtsc). -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.