From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 993CE6B00B6 for ; Wed, 10 Sep 2014 17:39:28 -0400 (EDT) Received: by mail-pa0-f45.google.com with SMTP id rd3so7848299pab.4 for ; Wed, 10 Sep 2014 14:39:28 -0700 (PDT) Received: from mail.zytor.com (terminus.zytor.com. [2001:1868:205::10]) by mx.google.com with ESMTPS id bd14si135872pdb.41.2014.09.10.14.39.27 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Sep 2014 14:39:27 -0700 (PDT) Message-ID: <5410C4F7.8050403@zytor.com> Date: Wed, 10 Sep 2014 14:39:03 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH v2 2/6] x86, mm, pat: Change reserve_memtype() to handle WT References: <1410367910-6026-1-git-send-email-toshi.kani@hp.com> <1410367910-6026-3-git-send-email-toshi.kani@hp.com> <1410377428.28990.260.camel@misato.fc.hp.com> <5410B10A.4030207@zytor.com> <1410381050.28990.295.camel@misato.fc.hp.com> <1410383484.28990.303.camel@misato.fc.hp.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andy Lutomirski , Toshi Kani Cc: Thomas Gleixner , Ingo Molnar , Andrew Morton , Arnd Bergmann , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Juergen Gross , Stefan Bader , Henrique de Moraes Holschuh , Yigal Korman , Konrad Rzeszutek Wilk On 09/10/2014 02:27 PM, Andy Lutomirski wrote: >> >> That's possible, but the only benefit is that we can enable WT on >> pre-PAT systems, which I do not think anyone cares now... WB & UC work >> on pre-PAT systems. WC & WT need PAT. I think this requirement is >> reasonable. > > It might end up being a cleanup, though. A whole bunch of > rarely-exercised if (!pat_enabled) things would go away. > Yes. Don't think of it as PAT vs non-PAT. Think of it as a specific set of cache types available on different processors. The fact that you may have to frob an MSR to initialize it is almost trivial in comparison. -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