From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761940Ab2COOhF (ORCPT ); Thu, 15 Mar 2012 10:37:05 -0400 Received: from terminus.zytor.com ([198.137.202.10]:56865 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761902Ab2COOhA (ORCPT ); Thu, 15 Mar 2012 10:37:00 -0400 Message-ID: <4F61FE7E.9060600@zytor.com> Date: Thu, 15 Mar 2012 07:36:46 -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> <4F61FC8E.8070109@zytor.com> <20120315143308.GA4382@srcf.ucam.org> In-Reply-To: <20120315143308.GA4382@srcf.ucam.org> X-Enigmail-Version: 1.4 Content-Type: text/plain; charset=ISO-8859-1 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 07:33 AM, Matthew Garrett wrote: >> >> 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... > > We've already mapped it at this point - we then go back and flag it UC > if it's not writeback. The latter seems to be causing problems, I'm not > sure we've seen any indication that the former is. And these regions are > marked as runtime accessible, so per spec they do need to be mapped into > address space... > In other words, it's totally f*cked. I guess at that point mapping it WB and letting the BIOS-configured MTRRs deal with the caching attributes is probably the right thing to do. I would still really like to understand why we're seeing #MCs... that's bothersome all by itself. -hpa