From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031267AbWKUSWP (ORCPT ); Tue, 21 Nov 2006 13:22:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031268AbWKUSWP (ORCPT ); Tue, 21 Nov 2006 13:22:15 -0500 Received: from outpipe-village-512-1.bc.nu ([81.2.110.250]:40407 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S1031267AbWKUSWO (ORCPT ); Tue, 21 Nov 2006 13:22:14 -0500 Date: Tue, 21 Nov 2006 18:27:26 +0000 From: Alan To: Andi Kleen Cc: Larry Finger , Ray Lee , linux-kernel@vger.kernel.org Subject: Re: Problem with DMA on x86_64 with 3 GB RAM Message-ID: <20061121182726.7d31451f@localhost.localdomain> In-Reply-To: <200611211746.39173.ak@suse.de> References: <455B63EC.8070704@madrabbit.org> <45632B30.9090506@lwfinger.net> <200611211746.39173.ak@suse.de> X-Mailer: Sylpheed-Claws 2.6.0 (GTK+ 2.8.20; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 21 Nov 2006 17:46:39 +0100 Andi Kleen wrote: > > > Shouldn't this problem be mentioned somewhere in the documentation, or did I miss something? The documentation is correct, the implementation is broken. The documented behaviour works for all platforms except one whose maintainer has a problem with it and refuses to follow the spec. > Possibly, but devices that cannot address at least 4GB are normally > categorized as "hardware bugs" (or less polite descriptions) and those don't > tend to get much airtime in documentation. The rest of the kernel deals with hardware limitations, 30bit DMA works on the other platforms. This is an x86-64 platform problem. It misimplements the basic pci_ functionality. If it doesn't wish to implement the stuff (and there btw Andi I do think your view has considerable merit) it should fail the set_mask requests. Alan