Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759417AbXEWXQh (ORCPT ); Wed, 23 May 2007 19:16:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756014AbXEWXQ3 (ORCPT ); Wed, 23 May 2007 19:16:29 -0400 Received: from shawidc-mo1.cg.shawcable.net ([24.71.223.10]:9409 "EHLO pd2mo1so.prod.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755631AbXEWXQ3 (ORCPT ); Wed, 23 May 2007 19:16:29 -0400 Date: Wed, 23 May 2007 17:15:42 -0600 From: Robert Hancock Subject: Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources In-reply-to: <200705231611.18944.jbarnes@virtuousgeek.org> To: Jesse Barnes Cc: David Miller , torvalds@linux-foundation.org, galibert@pobox.com, linux-kernel@vger.kernel.org, ak@suse.de, cebbert@redhat.com, lenb@kernel.org Message-id: <4654CB1E.3070409@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: <20070523.160415.26274543.davem@davemloft.net> <200705231611.18944.jbarnes@virtuousgeek.org> User-Agent: Thunderbird 2.0.0.0 (Windows/20070326) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1777 Lines: 36 Jesse Barnes wrote: > On Wednesday, May 23, 2007 4:04 pm David Miller wrote: >> From: Linus Torvalds >> Date: Wed, 23 May 2007 15:16:23 -0700 (PDT) >> >>> That crap should be seen for the crap it is! Dammit, how hard can >>> it be to just admit that mmconfig isn't that great? >> I knew mmconfig was broken conceptually the first time I started >> seeing write posting "bug fixes" for it that would do a read back >> from PCI config space via mmconfig to post the write, which of course >> has potential side-effects on the device and is absolutely illegal if >> the write just performed put the device into a PM state or whatever. > > I've actually seen that specific form of posted write flushing cause > crashes on some machines, so yes, it sucks. > > Unfortunately, I don't think we have any other way of getting at > extended config space on x86, unless EFI provides methods or something, > but I'm not sure that would be an improvement... That "fix" shouldn't be needed at all, the MMCONFIG memory range shouldn't be covered by PCI ordering rules, so there should be no such thing as write posting. I suspect that the author of such patch(es) was doing so out of some misguided sense that it was needed. (And if there is some chipset where it is actually needed, better just disable MMCONFIG on that one, as there's no way to use it sanely.) -- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/