Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755075Ab3EHWtS (ORCPT ); Wed, 8 May 2013 18:49:18 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45411 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752083Ab3EHWtR (ORCPT ); Wed, 8 May 2013 18:49:17 -0400 Message-ID: <518AD65E.1080509@zytor.com> Date: Wed, 08 May 2013 15:49:02 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Andy Lutomirski CC: Stefan Bader , Konrad Rzeszutek Wilk , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: WT memory type on x86_64? References: <20130508143505.GA8599@phenom.dumpdata.com> <518A6BF0.2060705@canonical.com> In-Reply-To: X-Enigmail-Version: 1.5.1 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: 800 Lines: 22 On 05/08/2013 09:37 AM, Andy Lutomirski wrote: >> >> Not sure whether this is the reason but UC and UC- (as well as WB) are kept like >> the backward compatible setup. So for systems with and without PAT cache types >> map to the same. Only WT gets replaced by WC. For that whenever PCD is set it >> means some uncached type. > > This also makes the pgprot_xyz macros faster -- they can do the same > thing regardless of PAT settings. > It also deals with errata in some very old CPUs... old enough that we don't use PAT on them anyway AFAIK. -hpa -- 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/