From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53447) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YTA85-0002jV-Qq for qemu-devel@nongnu.org; Wed, 04 Mar 2015 09:18:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YTA81-0007hZ-Ci for qemu-devel@nongnu.org; Wed, 04 Mar 2015 09:18:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33939) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YTA81-0007hH-6K for qemu-devel@nongnu.org; Wed, 04 Mar 2015 09:18:25 -0500 Message-ID: <1425475231.8389.63.camel@nilsson.home.kraxel.org> From: Gerd Hoffmann Date: Wed, 04 Mar 2015 14:20:31 +0100 In-Reply-To: <97fd6e025b9dfa941ea0d7677b52f66c@mail.shatteredsilicon.net> References: <97fd6e025b9dfa941ea0d7677b52f66c@mail.shatteredsilicon.net> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] QEMU etc/e820 and fw_cfg List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gordan Bobic Cc: qemu-devel@nongnu.org On Di, 2015-03-03 at 10:32 +0000, Gordan Bobic wrote: > I need to pass a custom e820 map to a virtual machine for > troubleshooting purposes and working around IOMMU hardware > bugs. > > I have found references to a custom map being providable > via an external file, mentioned as "etc/e820" and "fw_cfg". That is the (filesystem-like) interface between qemu and firmware (seabios usually), it doesn't refer to a on-disk file. > Unfortunately, I have not found any documentation that > explains how to use this from userspace when invoking > qemu. You can't. Passing a different e820 map requires patching qemu (or seabios, which mangles the e820 table to add reservations for acpi etc). What exactly do you need? cheers, Gerd