Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932236AbZJLUaA (ORCPT ); Mon, 12 Oct 2009 16:30:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754153AbZJLU37 (ORCPT ); Mon, 12 Oct 2009 16:29:59 -0400 Received: from mga03.intel.com ([143.182.124.21]:39233 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751402AbZJLU37 (ORCPT ); Mon, 12 Oct 2009 16:29:59 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,547,1249282800"; d="scan'208";a="198061481" Subject: Re: 2.6.32-rc4: Reported regressions from 2.6.31 From: David Woodhouse To: Linus Torvalds Cc: "Rafael J. Wysocki" , Greg Kroah-Hartman , Linux Kernel Mailing List , Adrian Bunk , Andrew Morton , Natalie Protasevich In-Reply-To: References: <1255342738.24732.265.camel@macbook.infradead.org> <1255362962.32729.63.camel@macbook.infradead.org> Content-Type: text/plain; charset="UTF-8" Organization: Intel Corporation. Pipers Way, Swindon, Wiltshire, SN3 1RJ, UK. Date: Mon, 12 Oct 2009 21:29:19 +0100 Message-Id: <1255379359.32729.625.camel@macbook.infradead.org> Mime-Version: 1.0 X-Mailer: Evolution 2.28.0 (2.28.0-2.fc12) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1809 Lines: 40 On Mon, 2009-10-12 at 18:35 +0100, Linus Torvalds wrote: > > On Mon, 12 Oct 2009, David Woodhouse wrote: > > > > > The other solution would be to just _enable_ (and do all the setup) of the > > > IOMMU early. And then just leave a legacy mapping for the IOMMU, and then > > > _after_all_devices_are_set_up_ can you then remove the legacy mapping. > > > > That involves allocating a _shitload_ of page tables for a 1:1 mapping > > of all of physical memory. > > I don't think that's true. > > Nobody cares about "all physical memory". For one thing, we know that > anything that we consider to be normal memory (ie it's listed in the e820 > tables as RAM) can't be all that interesting, since the BIOS definitely > released that to us. Yeah, that's probably true. I was thinking of the 1:1 mappings we set up for crappy drivers under Linux, which do need access to all of memory and don't use the DMA API correctly. This is different, though. We have talked about dma-mapping all of E820-reserved memory, but that would allow a rogue device to scribble over arbitrary bits of memory belonging to the BIOS, which isn't necessarily such a good thing. Even if we did tear it down as soon as a real driver came along, the TXT folks would still object -- and rightly so. As you said, it's sufficient just to enable the IOMMU after the quirks have run. So the patches I posted earlier should be just fine. -- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation -- 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/