From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757104Ab2COOHT (ORCPT ); Thu, 15 Mar 2012 10:07:19 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:52279 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752121Ab2COOHQ (ORCPT ); Thu, 15 Mar 2012 10:07:16 -0400 Date: Thu, 15 Mar 2012 14:07:08 +0000 From: Matthew Garrett To: "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, x86@kernel.org, matt.fleming@intel.com Subject: Re: [PATCH] EFI: Only set regions uncacheable if they support it Message-ID: <20120315140708.GA3395@srcf.ucam.org> References: <1331819798-1955-1-git-send-email-mjg@redhat.com> <4F61F5E6.8060509@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F61F5E6.8060509@zytor.com> User-Agent: Mutt/1.5.20 (2009-06-14) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: mjg59@cavan.codon.org.uk X-SA-Exim-Scanned: No (on cavan.codon.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2012 at 07:00:06AM -0700, H. Peter Anvin wrote: > On 03/15/2012 06:56 AM, Matthew Garrett wrote: > > The EFI memory region attributes field indicates whether the region can > > be mapped with various cache attributes. Our current implementation always > > marks regions uncacheable if they don't have the writeback support flag. > > This causes us to mark some regions uncacheable even if they don't > > indicate support for being uncacheable, triggering a clflush that may cause > > an MCE. Ensure we only do this for regions which support it. > > > > Signed-off-by: Matthew Garrett > > Could you be specific as to what you're seeing in the field? In > particular, what *do* these memory regions claim to support? I have a report of a system that fails to boot with an MCE during EFI setup. The memory range is marked reserved and claims not to support any caching type, which I think probably translates as "Don't do anything to this region ever". -- Matthew Garrett | mjg59@srcf.ucam.org