Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756490AbXKAQ4S (ORCPT ); Thu, 1 Nov 2007 12:56:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753005AbXKAQ4G (ORCPT ); Thu, 1 Nov 2007 12:56:06 -0400 Received: from mta2.cl.cam.ac.uk ([128.232.0.14]:55136 "EHLO mta2.cl.cam.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752792AbXKAQ4F (ORCPT ); Thu, 1 Nov 2007 12:56:05 -0400 X-Greylist: delayed 2861 seconds by postgrey-1.27 at vger.kernel.org; Thu, 01 Nov 2007 12:56:05 EDT User-Agent: Microsoft-Entourage/11.3.6.070618 Date: Thu, 01 Nov 2007 16:07:40 +0000 Subject: Re: [PATCH 3/16] read/write_crX, clts and wbinvd for 64-bit paravirt From: Keir Fraser To: Jeremy Fitzhardinge , Glauber de Oliveira Costa CC: , , , , , , , , , Message-ID: Thread-Topic: [PATCH 3/16] read/write_crX, clts and wbinvd for 64-bit paravirt Thread-Index: AcgcoVO4kkHFmoiUEdy2TAAX8io7RQ== In-Reply-To: <4729F133.3060308@goop.org> Mime-version: 1.0 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 777 Lines: 21 On 1/11/07 15:30, "Jeremy Fitzhardinge" wrote: > Glauber de Oliveira Costa wrote: >> I in fact have seen bugs with mixed reads and writes to the same cr, >> (cr4), but adding the volatile >> flag to the read function seemed to fix it. > > Well, volatile will make a read be repeated rather than caching the > previous value, but it has no effect on ordering. volatile prevents the asm from being 'moved significantly', according to the gcc manual. I take that to mean that reordering is not allowed. -- Keir - 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/