From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751266AbaIEPxX (ORCPT ); Fri, 5 Sep 2014 11:53:23 -0400 Received: from g6t1524.atlanta.hp.com ([15.193.200.67]:17366 "EHLO g6t1524.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750776AbaIEPxW (ORCPT ); Fri, 5 Sep 2014 11:53:22 -0400 Message-ID: <1409931772.28990.197.camel@misato.fc.hp.com> Subject: Re: [PATCH 1/5] x86, mm, pat: Set WT to PA4 slot of PAT MSR From: Toshi Kani To: "H. Peter Anvin" Cc: Andy Lutomirski , Henrique de Moraes Holschuh , Thomas Gleixner , Ingo Molnar , akpm@linuxfoundation.org, Arnd Bergmann , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Juergen Gross , Stefan Bader , Konrad Rzeszutek Wilk Date: Fri, 05 Sep 2014 09:42:52 -0600 In-Reply-To: <5409D99C.10305@zytor.com> References: <1409855739-8985-1-git-send-email-toshi.kani@hp.com> <1409855739-8985-2-git-send-email-toshi.kani@hp.com> <20140904201123.GA9116@khazad-dum.debian.net> <5408C9C4.1010705@zytor.com> <20140904231923.GA15320@khazad-dum.debian.net> <1409876991.28990.172.camel@misato.fc.hp.com> <1409925614.28990.184.camel@misato.fc.hp.com> <5409D197.2060900@zytor.com> <1409930574.28990.192.camel@misato.fc.hp.com> <5409D99C.10305@zytor.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5 (3.8.5-2.fc19) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2014-09-05 at 08:41 -0700, H. Peter Anvin wrote: > On 09/05/2014 08:22 AM, Toshi Kani wrote: > > On Fri, 2014-09-05 at 08:07 -0700, H. Peter Anvin wrote: > >> On 09/05/2014 07:00 AM, Toshi Kani wrote: > >>> > >>> That's a fine idea, but as Ingo also suggested, I am going to disable > >>> this feature on all Pentium 4 models. That should give us a safety > >>> margin. Using slot 4 has a benefit that it keeps the PAT setup > >>> consistent with Xen. > >>> > >> > >> Slot 4 is also the maximally problematic one, because it is the one that > >> might be incorrectly invoked for the page tables themselves. > > > > Good point. I wonder if Xen folks feel strongly about keeping the PAT > > setup consistent with the kernel. If not, we may choose to use slot 6 > > (or 7). > > > > Who cares what the Xen folks "feel strongly about"? If strong feelings > were a design criterion Xen support would have been pulled from the > kernel a long, long time ago. > > The important thing is how to design for the situation that we currently > have to live with. I see. Then, I am going to use slot 7 for WT as suggested by Andy. I think it is the safest slot as slot 3 is UC and is not currently used. Thanks, -Toshi