From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH V2 RFC] fixup! virtio: convert to use DMA api Date: Mon, 9 May 2016 13:09:24 +0200 Message-ID: <57306FE4.4050006@redhat.com> References: <20160427153345-mutt-send-email-mst@redhat.com> <20160427142331.GH17926@8bytes.org> <20160427172630-mutt-send-email-mst@redhat.com> <20160427145632.GI17926@8bytes.org> <20160427180007-mutt-send-email-mst@redhat.com> <1461770135.118304.152.camel@infradead.org> <20160427211635-mutt-send-email-mst@redhat.com> <1461784617.118304.181.camel@infradead.org> <20160428172039-mutt-send-email-mst@redhat.com> <1461856314.33870.98.camel@infradead.org> <20160428182341-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160428182341-mutt-send-email-mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "Michael S. Tsirkin" , David Woodhouse Cc: Kevin Wolf , cornelia.huck-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org, Wei Liu , Stefan Hajnoczi , qemu-block-qX2TKyscuCcdnm+yROfE0A@public.gmane.org, Stefano Stabellini , qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org, peterx-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christian Borntraeger , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Andy Lutomirski , kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Amit Shah , virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Anthony PERARD , Jason Wang List-Id: iommu@lists.linux-foundation.org On 28/04/2016 17:37, Michael S. Tsirkin wrote: > > All the internally-emulated devices *can* be either translated or > > untranslated. That's just a matter of software. Surely, you currently > > *can't* have translated assigned devices (until someone implements the > > whole VT-d page table shadowing or whatever), so you'll be barred from > > assigning a device to a slot which *previously* had an untranslated > > device. But so what? Put it in a different slot instead. > > Unfortunately people got used to be able to put any device > in any slot, and built external tools around that ability. > It's rather painful to break this assumption. Once you move to PCIe, a lot of things become more complicated. This is just one of them; instead of needing half a dozen PCI bridges, you'll need half a dozen plus one. Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752048AbcEILJf (ORCPT ); Mon, 9 May 2016 07:09:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40912 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751252AbcEILJd (ORCPT ); Mon, 9 May 2016 07:09:33 -0400 Subject: Re: [PATCH V2 RFC] fixup! virtio: convert to use DMA api To: "Michael S. Tsirkin" , David Woodhouse References: <20160427153345-mutt-send-email-mst@redhat.com> <20160427142331.GH17926@8bytes.org> <20160427172630-mutt-send-email-mst@redhat.com> <20160427145632.GI17926@8bytes.org> <20160427180007-mutt-send-email-mst@redhat.com> <1461770135.118304.152.camel@infradead.org> <20160427211635-mutt-send-email-mst@redhat.com> <1461784617.118304.181.camel@infradead.org> <20160428172039-mutt-send-email-mst@redhat.com> <1461856314.33870.98.camel@infradead.org> <20160428182341-mutt-send-email-mst@redhat.com> Cc: Joerg Roedel , Kevin Wolf , Wei Liu , Andy Lutomirski , qemu-block@nongnu.org, Christian Borntraeger , Jason Wang , Stefano Stabellini , qemu-devel@nongnu.org, peterx@redhat.com, linux-kernel@vger.kernel.org, Amit Shah , iommu@lists.linux-foundation.org, Stefan Hajnoczi , kvm@vger.kernel.org, cornelia.huck@de.ibm.com, virtualization@lists.linux-foundation.org, Anthony PERARD From: Paolo Bonzini Message-ID: <57306FE4.4050006@redhat.com> Date: Mon, 9 May 2016 13:09:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.1 MIME-Version: 1.0 In-Reply-To: <20160428182341-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/04/2016 17:37, Michael S. Tsirkin wrote: > > All the internally-emulated devices *can* be either translated or > > untranslated. That's just a matter of software. Surely, you currently > > *can't* have translated assigned devices (until someone implements the > > whole VT-d page table shadowing or whatever), so you'll be barred from > > assigning a device to a slot which *previously* had an untranslated > > device. But so what? Put it in a different slot instead. > > Unfortunately people got used to be able to put any device > in any slot, and built external tools around that ability. > It's rather painful to break this assumption. Once you move to PCIe, a lot of things become more complicated. This is just one of them; instead of needing half a dozen PCI bridges, you'll need half a dozen plus one. Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56447) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1azj4G-0003M9-C0 for qemu-devel@nongnu.org; Mon, 09 May 2016 07:09:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1azj4E-0001Rf-C6 for qemu-devel@nongnu.org; Mon, 09 May 2016 07:09:39 -0400 References: <20160427153345-mutt-send-email-mst@redhat.com> <20160427142331.GH17926@8bytes.org> <20160427172630-mutt-send-email-mst@redhat.com> <20160427145632.GI17926@8bytes.org> <20160427180007-mutt-send-email-mst@redhat.com> <1461770135.118304.152.camel@infradead.org> <20160427211635-mutt-send-email-mst@redhat.com> <1461784617.118304.181.camel@infradead.org> <20160428172039-mutt-send-email-mst@redhat.com> <1461856314.33870.98.camel@infradead.org> <20160428182341-mutt-send-email-mst@redhat.com> From: Paolo Bonzini Message-ID: <57306FE4.4050006@redhat.com> Date: Mon, 9 May 2016 13:09:24 +0200 MIME-Version: 1.0 In-Reply-To: <20160428182341-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , David Woodhouse Cc: Joerg Roedel , Kevin Wolf , Wei Liu , Andy Lutomirski , qemu-block@nongnu.org, Christian Borntraeger , Jason Wang , Stefano Stabellini , qemu-devel@nongnu.org, peterx@redhat.com, linux-kernel@vger.kernel.org, Amit Shah , iommu@lists.linux-foundation.org, Stefan Hajnoczi , kvm@vger.kernel.org, cornelia.huck@de.ibm.com, virtualization@lists.linux-foundation.org, Anthony PERARD On 28/04/2016 17:37, Michael S. Tsirkin wrote: > > All the internally-emulated devices *can* be either translated or > > untranslated. That's just a matter of software. Surely, you currently > > *can't* have translated assigned devices (until someone implements the > > whole VT-d page table shadowing or whatever), so you'll be barred from > > assigning a device to a slot which *previously* had an untranslated > > device. But so what? Put it in a different slot instead. > > Unfortunately people got used to be able to put any device > in any slot, and built external tools around that ability. > It's rather painful to break this assumption. Once you move to PCIe, a lot of things become more complicated. This is just one of them; instead of needing half a dozen PCI bridges, you'll need half a dozen plus one. Paolo