From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760064Ab2COO2l (ORCPT ); Thu, 15 Mar 2012 10:28:41 -0400 Received: from terminus.zytor.com ([198.137.202.10]:56799 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756015Ab2COO2k (ORCPT ); Thu, 15 Mar 2012 10:28:40 -0400 Message-ID: <4F61FC8E.8070109@zytor.com> Date: Thu, 15 Mar 2012 07:28:30 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120209 Thunderbird/10.0.1 MIME-Version: 1.0 To: Matthew Garrett 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 References: <1331819798-1955-1-git-send-email-mjg@redhat.com> <4F61F5E6.8060509@zytor.com> <20120315140708.GA3395@srcf.ucam.org> <4F61FA14.6020203@zytor.com> <20120315142445.GA4357@srcf.ucam.org> In-Reply-To: <20120315142445.GA4357@srcf.ucam.org> X-Enigmail-Version: 1.3.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/15/2012 07:24 AM, Matthew Garrett wrote: > On Thu, Mar 15, 2012 at 07:17:56AM -0700, H. Peter Anvin wrote: >> On 03/15/2012 07:07 AM, Matthew Garrett wrote: >>> >>> 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". >>> >> >> In other words, "don't map me"... not something we really support at the >> moment, but perhaps we should; at least until we find systems in the >> field that break with that constraint :( > > Mapping should be harmless as long as we then don't touch it? I can't > think of any circumstances where we would. > If we map it WB software can do speculative loads from that region which would bring it into the cache. If we map it UC we might have to CLFLUSH... -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.