From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758061AbbICSKS (ORCPT ); Thu, 3 Sep 2015 14:10:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40373 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755913AbbICSKQ (ORCPT ); Thu, 3 Sep 2015 14:10:16 -0400 Message-ID: <55E88D06.3040608@redhat.com> Date: Thu, 03 Sep 2015 14:10:14 -0400 From: Prarit Bhargava User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: "Luis R. Rodriguez" CC: Stuart Hayes , tglx@linutronix.de, mingo@redhat.com, "H. Peter Anvin" , linux-kernel@vger.kernel.org, x86@kernel.org, mcgrof@do-not-panic.com, Toshi Kani Subject: Re: Fwd: [PATCH] x86: Use larger chunks in mtrr_cleanup References: <55E477DE.2060106@gmail.com> <55E47B4D.1050103@gmail.com> <20150903024542.GS8051@wotan.suse.de> <55E83A3E.3030000@redhat.com> <20150903175902.GU8051@wotan.suse.de> In-Reply-To: <20150903175902.GU8051@wotan.suse.de> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/03/2015 01:59 PM, Luis R. Rodriguez wrote: > On Thu, Sep 03, 2015 at 08:17:02AM -0400, Prarit Bhargava wrote: >> >> >> On 09/02/2015 10:45 PM, Luis R. Rodriguez wrote: >>> On Mon, Aug 31, 2015 at 11:05:33AM -0500, Stuart Hayes wrote: >>>> Increase the range of chunk sizes tried in mtrr_cleanup() so it is able >>>> to map large memory configs into MTRRs. >>>> >>>> Currently, mtrr_cleanup() will fail with large memory configurations, >>>> because it limits chunk_size to 2GB, which means that each MTRR can only >>>> cover 2GB of memory. With a memory size of, say, 256GB, and ten variable >>>> MTRRs (such as some recent Intel CPUs have), it is not possible to set up >>>> the MTRRs to cover all of memory. >>> >>> Linux drivers no longer use MTRR so why is the cleanup needed, ie, what would >>> happen if the cleanup is just skipped in your case ? >> >> The infiniband & video drivers still use MTRR (or at least it was my >> understanding that they do). > > There were a few stragglers left on v4.2, I have transformed them in the latest > development changes and those tranformations are now part of linux-next. If > this is specific to a driver you may want to first ensure you backport the > required patch that transforms the driver to use proper PAT interfaces, v4.2 > should have most updates but there were still a few left. Just make sure your > driver doesn't call mtrr_add() directly and if it doesn't then you should be > OK. > >> In any case, Stuart -- could you try booting with >> 'disable_mtrr_cleanup' as a kernel parameter? > > Indeed, please I'd like to hear back. Be sure to have the respective driver > transformation in place, what driver are you using exactly? In the event that > you argue this is still needed I'd like to know exaclty *why*, the comit log > does not mention any of that at all. > Well ... we are trying to also fix this in older kernels too, *cough* RHEL *cough*, so that's where the patch comes from. If upstream is going to deprecate/remove mtrr support so be it. We can do a stable fix instead to fix older stable kernels. P.