From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) by kanga.kvack.org (Postfix) with ESMTP id 097A46B006E for ; Mon, 21 Jul 2014 13:30:32 -0400 (EDT) Received: by mail-pa0-f48.google.com with SMTP id et14so10120998pad.7 for ; Mon, 21 Jul 2014 10:30:32 -0700 (PDT) Received: from g2t2354.austin.hp.com (g2t2354.austin.hp.com. [15.217.128.53]) by mx.google.com with ESMTPS id jt4si7928210pbc.115.2014.07.21.10.30.31 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 21 Jul 2014 10:30:32 -0700 (PDT) Message-ID: <1405963247.31023.0.camel@misato.fc.hp.com> Subject: Re: [RFC PATCH 0/11] Support Write-Through mapping on x86 From: Toshi Kani Date: Mon, 21 Jul 2014 11:20:47 -0600 In-Reply-To: <53CD443A.6050804@zytor.com> References: <1405452884-25688-1-git-send-email-toshi.kani@hp.com> <53C58A69.3070207@zytor.com> <1405459404.28702.17.camel@misato.fc.hp.com> <03d059f5-b564-4530-9184-f91ca9d5c016@email.android.com> <1405546127.28702.85.camel@misato.fc.hp.com> <1405960298.30151.10.camel@misato.fc.hp.com> <53CD443A.6050804@zytor.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "H. Peter Anvin" Cc: Konrad Rzeszutek Wilk , tglx@linutronix.de, mingo@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, plagnioj@jcrosoft.com, tomi.valkeinen@ti.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stefan.bader@canonical.com, luto@amacapital.net, airlied@gmail.com, bp@alien8.de On Mon, 2014-07-21 at 09:47 -0700, H. Peter Anvin wrote: > On 07/21/2014 09:31 AM, Toshi Kani wrote: > > Do you have any comments / suggestions for this approach? > > Approach to what, specifically? > > Keep in mind the PAT bit is different for large pages. This needs to be > dealt with. You are right. I was under a wrong impression that __change_page_attr() always splits a large pages into 4KB pages, but I overlooked the fact that it can handle a large page as well. So, this approach does not work... > I would also like a systematic way to deal with the fact > that Xen (sigh) is stuck with a separate mapping system. > > I guess Linux could adopt the Xen mappings if that makes it easier, as > long as that doesn't have a negative impact on native hardware -- we can > possibly deal with some older chips not being optimal. I see. I agree that supporting the PAT bit is the right direction, but I do not know how much effort we need. I will study on this. > However, my thinking has been to have a "reverse PAT" table in memory of memory > types to encodings, both for regular and large pages. I am not clear about your idea of the "reverse PAT" table. Would you care to elaborate? How is it different from using pte_val() being a paravirt function on Xen? Thanks, -Toshi -- 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