From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754592AbYHMGBb (ORCPT ); Wed, 13 Aug 2008 02:01:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751868AbYHMGBY (ORCPT ); Wed, 13 Aug 2008 02:01:24 -0400 Received: from terminus.zytor.com ([198.137.202.10]:55355 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751784AbYHMGBX (ORCPT ); Wed, 13 Aug 2008 02:01:23 -0400 Message-ID: <48A278AE.1070800@zytor.com> Date: Tue, 12 Aug 2008 23:01:18 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Chris Adams CC: linux-kernel@vger.kernel.org Subject: Re: AGP aperture beyond 4GB not valid? References: <20080813013255.GD633804@hiwaay.net> In-Reply-To: <20080813013255.GD633804@hiwaay.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Chris Adams wrote: > > Checking aperture... > Node 0: aperture @ 1006000000 size 32 MB > Aperture beyond 4GB. Ignoring. > No AGP bridge found > Your BIOS doesn't leave a aperture memory hole > Please enable the IOMMU option in the BIOS setup > This costs you 64 MB of RAM > Mapping aperture over 65536 KB of RAM @ c000000 > PM: Registered nosave memory: 000000000c000000 - 0000000010000000 > > > My BIOS doesn't have an IOMMU option (latest BIOS available for the > mboard). However, it appears that an aperture is allocated but the > kernel then ignores it due to where it is placed. Why? > You can't use it as an IOMMU to handle 32-bit devices, since it's above the 32-bit addressible region. Hence the kernel doesn't use it. -hpa