From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oa0-f45.google.com (mail-oa0-f45.google.com [209.85.219.45]) by kanga.kvack.org (Postfix) with ESMTP id AB3D66B0036 for ; Fri, 5 Sep 2014 11:41:57 -0400 (EDT) Received: by mail-oa0-f45.google.com with SMTP id n16so8629975oag.32 for ; Fri, 05 Sep 2014 08:41:57 -0700 (PDT) Received: from mail.zytor.com (terminus.zytor.com. [2001:1868:205::10]) by mx.google.com with ESMTPS id jy10si4811535pbc.150.2014.09.05.08.41.55 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 05 Sep 2014 08:41:55 -0700 (PDT) Message-ID: <5409D99C.10305@zytor.com> Date: Fri, 05 Sep 2014 08:41:16 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH 1/5] x86, mm, pat: Set WT to PA4 slot of PAT MSR 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> In-Reply-To: <1409930574.28990.192.camel@misato.fc.hp.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani 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 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. -hpa -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org