From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:54934) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QJvfi-000856-K9 for qemu-devel@nongnu.org; Tue, 10 May 2011 18:44:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QJvfh-00025g-Pq for qemu-devel@nongnu.org; Tue, 10 May 2011 18:44:54 -0400 Received: from mail.codesourcery.com ([38.113.113.100]:49763) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QJvfh-00025a-Ff for qemu-devel@nongnu.org; Tue, 10 May 2011 18:44:53 -0400 From: Paul Brook Date: Tue, 10 May 2011 23:44:49 +0100 References: <1304976889-29675-1-git-send-email-rth@twiddle.net> <201105102233.28788.paul@codesourcery.com> <4DC9B795.2030904@twiddle.net> In-Reply-To: <4DC9B795.2030904@twiddle.net> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201105102344.49793.paul@codesourcery.com> Subject: Re: [Qemu-devel] [PATCH 00/35] Alpha system emulation, v4 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Richard Henderson > On 05/10/2011 02:33 PM, Paul Brook wrote: > > There should be nothing special about virtio-pci. These devices should > > access memory in exactly the same way as any other PCI device. Bypassing > > the normal PCI iommu is IMO a serious bug. > > I suspect that the argument is that virtio is implemented on several > busses, and ignoring any bus-specific stuff means that there's less > need for any code differences. It also has some horrifically bad implications. Not least of which is the inability to sanely handle nested virtualization. IMO the whole point of virtio-pci is that it avoids magical weirdness for virtio devices devices. If you're going to start adding nonstandard exceptions for virtio devices than there seem little point using PCI in the first place. It's likely to cause more problems than it solves for the guest drivers. Paul