From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754169AbaIHSwg (ORCPT ); Mon, 8 Sep 2014 14:52:36 -0400 Received: from g4t3426.houston.hp.com ([15.201.208.54]:6955 "EHLO g4t3426.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750992AbaIHSwf (ORCPT ); Mon, 8 Sep 2014 14:52:35 -0400 Message-ID: <1410201722.28990.219.camel@misato.fc.hp.com> Subject: Re: [PATCH 4/5] x86, mm: Add set_memory_wt() for WT From: Toshi Kani To: Andy Lutomirski Cc: "linux-mm@kvack.org" , Yigal Korman , Juergen Gross , Arnd Bergmann , Thomas Gleixner , akpm@linuxfoundation.org, Ingo Molnar , "linux-kernel@vger.kernel.org" , "H. Peter Anvin" , Konrad Rzeszutek Wilk , Stefan Bader Date: Mon, 08 Sep 2014 12:42:02 -0600 In-Reply-To: References: <1409855739-8985-1-git-send-email-toshi.kani@hp.com> <1409855739-8985-5-git-send-email-toshi.kani@hp.com> <1409857025.28990.125.camel@misato.fc.hp.com> <540C1C01.1000308@plexistor.com> <1410188863.28990.209.camel@misato.fc.hp.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 Mon, 2014-09-08 at 10:23 -0700, Andy Lutomirski wrote: > On Sep 8, 2014 8:18 AM, "Toshi Kani" wrote: > > > > On Sun, 2014-09-07 at 09:49 -0700, Andy Lutomirski wrote: > > > On Sun, Sep 7, 2014 at 1:49 AM, Yigal Korman wrote: > > > > I think that what confused Andy (or at least me) is the documentation in Documentation/x86/pat.txt > > > > If it's possible, can you please update pat.txt as part of the patch? > > > > > > Indeed. That file seems to indicate several times that the intended > > > use of set_memory_xyz is for RAM. > > > > > > Good point. pat.txt is correct that the "intended" use of > > set_memory_xyz() is for RAM since there is no other way to set non-WB > > attribute for RAM. For reserved memory, one should call ioremap_xyz() > > to map with the xyz attribute directly. From the functionality POV, > > set_memory_xyz() works for reserved memory, but such usage is not > > intended. > > > > Should I drop the patch 4/5 until we can track the use of WT for RAM? > > Probably not. I can imagine someone ioremapping a huge chunk of > NV-DIMM and then wanting to change some of it to WT. Unless I've > missed something (which is rather likely), the cleanest way to do this > is with set_memory_wt. Yeah, that sounds possible. > If that happens, someone should update pat.txt to indicate that it's allowed. Since it is unlikely that someone will update pat.txt later, I will update it to: ------------------------------------------------------------------- API | RAM | ACPI,... | Reserved/Holes | -----------------------|----------|------------|------------------| set_memory_wt | *1 | -- | WT | set_memory_wb | | | | *1: -EINVAL due to the current limitation in reserve_memtype(). Thanks, -Toshi