From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757147Ab2JWQFH (ORCPT ); Tue, 23 Oct 2012 12:05:07 -0400 Received: from g5t0006.atlanta.hp.com ([15.192.0.43]:17622 "EHLO g5t0006.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754531Ab2JWQFF (ORCPT ); Tue, 23 Oct 2012 12:05:05 -0400 From: Randy Wright Message-Id: <201210231605.q9NG51KW022791@filesys1.fc.hp.com> Subject: Re: [PATCH RFC] function probe_roms accessing improper addresses To: mjg@redhat.com (Matthew Garrett) Date: Tue, 23 Oct 2012 10:05:01 -0600 (MDT) Cc: rwright@hp.com, linux-kernel@vger.kernel.org, tmac@hp.com, hpa@zytor.com, mjg59@srcf.ucam.org Reply-To: rwright@hp.com In-Reply-To: <20121019153015.GD28212@srcf.ucam.org> from "Matthew Garrett" at Oct 19, 2012 04:30:15 pm Organization: Hewlett-Packard/Mission Critical Open Source Development Lab X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Matthew, You made some interesting suggestions: > 1) Declare that any x86 hardware supported by Linux *must* support > probing in this address region On the first: one way to be compliant with such a requirement would be to design systems that implement softfail in this particular region. What about a system that hardfails, but on which the resulting machine check can be handled by the kernel machine check handler? Would appropriate re-ordering of the kernel initialization code to support such systems be acceptable? Also, let me mention a possible amendment to your first idea: what if the mandate that probing be supported were qualified by some attribute that could be indicated in the UEFI environment? For example: instead of just a hole in the UEFI memory map, what if this range was specifically present and typed as EfiUnusableMemory? Another idea for UEFI systems - but one requiring a UEFI specification change - might be adding a UEFI variable that if present, indicates any area not explicitly included and typed in the UEFI memory map (including the legacy adapter region) must be explicitly avoided by an OS. > 2) Don't call probe_roms() by default, but leave it up to the graphics > drivers. If they can get the rom by any other means then don't call it. One the second idea: there are a quite a lot of video drivers in the kernel source tree. Do you have a suggestion for how to evaluate which ones rely on the setup performed by probe_roms? -- Randy Wright Hewlett-Packard Company Phone: (970) 898-0998 Mail: rwright@hp.com