From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH qemu-kvm] device assignment: default requires IOMMU Date: Mon, 18 Jan 2010 16:20:34 +0200 Message-ID: <4B546E32.3030507@redhat.com> References: <20091223224020.GB3305@sequoia.sous-sol.org> <4B546DA1.4050107@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Chris Wright , Marcelo Tosatti , kvm@vger.kernel.org, Dmitri Seletski , Sheng Yang To: Alexander Graf Return-path: Received: from mx1.redhat.com ([209.132.183.28]:62506 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752770Ab0AROUs (ORCPT ); Mon, 18 Jan 2010 09:20:48 -0500 In-Reply-To: <4B546DA1.4050107@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: On 01/18/2010 04:18 PM, Alexander Graf wrote: > Chris Wright wrote: > >> [ resend, fixing email header, sorry for duplicate ] >> >> The default mode for device assignment is to rely on an IOMMU for >> proper translations and a functioning device in the guest. The current >> logic makes this requirement advisory, and simply disables the request >> for IOMMU if one is not found on the host. This makes for a confused >> user when the device assignment appears to work, but the device in the >> guest is not functioning (I've seen about a half-dozen reports with >> this failure mode). >> >> Change the logic such that the default requires the IOMMU. Period. >> If the host does not have an IOMMU, device assignment will fail. >> >> This is a user visible change, however I think the current situation is >> simply broken. >> >> And, of course, disabling the IOMMU requirement using the old: >> >> -pcidevice host=[addr],dma=none >> >> or the newer: >> >> -device pci-assign,host=[addr],iommu=0 >> >> will do what it always did (not require an IOMMU, and fail to work >> properly). >> >> > Avi, > > could you please cherry-pick this into 0.12-stable? > I don't feel too eager getting 500 bug reports from people who try out > device passthrough with disabled or no IOMMU. > > Makes sense. Marcelo is committing this week, though. -- error compiling committee.c: too many arguments to function