From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755394Ab0GXApw (ORCPT ); Fri, 23 Jul 2010 20:45:52 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:48803 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751718Ab0GXApv (ORCPT ); Fri, 23 Jul 2010 20:45:51 -0400 Date: Sat, 24 Jul 2010 01:45:32 +0100 From: Matthew Garrett To: Henrique de Moraes Holschuh Cc: Jack Steiner , mingo@elte.hu, tglx@linutronix.de, lenb@kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC] - Mapping ACPI tables as CACHED Message-ID: <20100724004532.GA9240@srcf.ucam.org> References: <20100722152220.GA18290@sgi.com> <20100724001449.GA9618@khazad-dum.debian.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100724001449.GA9618@khazad-dum.debian.net> User-Agent: Mutt/1.5.18 (2008-05-17) 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 Fri, Jul 23, 2010 at 09:14:50PM -0300, Henrique de Moraes Holschuh wrote: > Well, as it was raised in this thread, ACPI tables are likely to be near RAM > regions used for IPC with the firmware or SMBIOS, and we have no idea of the > kind of crap that could happen if we enable caching on those areas. > > OTOH, we *know* of systems that force us to copy the ACPI tables to regular > RAM, otherwise, the utterly broken BIOS corrupts the ACPI tables after the > kernel has loaded. > > Couldn't we simply always copy all tables to regular RAM and mark THAT as > cacheable (since there will be no IPC regions in it)? For the tables that > are only used once, we can free the RAM later. I think this is reasonable. There's an argument that we shouldn't cache operation regions that may be sitting next to the ACPI tables, but I can't see any problems being caused by copying the tables to RAM. -- Matthew Garrett | mjg59@srcf.ucam.org