From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759302AbbKSV72 (ORCPT ); Thu, 19 Nov 2015 16:59:28 -0500 Received: from mail-ob0-f172.google.com ([209.85.214.172]:34236 "EHLO mail-ob0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757831AbbKSV70 (ORCPT ); Thu, 19 Nov 2015 16:59:26 -0500 MIME-Version: 1.0 In-Reply-To: <20151119153821-mutt-send-email-mst@redhat.com> References: <20151119153821-mutt-send-email-mst@redhat.com> From: Andy Lutomirski Date: Thu, 19 Nov 2015 13:59:05 -0800 Message-ID: Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff To: "Michael S. Tsirkin" Cc: Benjamin Herrenschmidt , Christian Borntraeger , Paolo Bonzini , "linux-kernel@vger.kernel.org" , Martin Schwidefsky , Sebastian Ott , linux-s390 , Cornelia Huck , Joerg Roedel , Linux Virtualization , Christoph Hellwig , David Woodhouse , KVM Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Nov 19, 2015 5:45 AM, "Michael S. Tsirkin" wrote: > > On Tue, Oct 27, 2015 at 11:38:57PM -0700, Andy Lutomirski wrote: > > This switches virtio to use the DMA API unconditionally. I'm sure > > it breaks things, but it seems to work on x86 using virtio-pci, with > > and without Xen, and using both the modern 1.0 variant and the > > legacy variant. > > So thinking hard about it, I don't see any real drawbacks to making this > conditional on a new feature bit, that Xen can then set.. Can you elaborate? If I run QEMU, hosting Xen, hosting Linux, and the virtio device is provided by QEMU, then how does Xen set the bit? Similarly, how would Xen set the bit for a real physical device? --Andy From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff Date: Thu, 19 Nov 2015 13:59:05 -0800 Message-ID: References: <20151119153821-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: <20151119153821-mutt-send-email-mst@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Archive: List-Post: To: "Michael S. Tsirkin" Cc: linux-s390 , KVM , Benjamin Herrenschmidt , Sebastian Ott , "linux-kernel@vger.kernel.org" , Linux Virtualization , Christian Borntraeger , Joerg Roedel , Martin Schwidefsky , Paolo Bonzini , David Woodhouse , Christoph Hellwig List-ID: On Nov 19, 2015 5:45 AM, "Michael S. Tsirkin" wrote: > > On Tue, Oct 27, 2015 at 11:38:57PM -0700, Andy Lutomirski wrote: > > This switches virtio to use the DMA API unconditionally. I'm sure > > it breaks things, but it seems to work on x86 using virtio-pci, with > > and without Xen, and using both the modern 1.0 variant and the > > legacy variant. > > So thinking hard about it, I don't see any real drawbacks to making this > conditional on a new feature bit, that Xen can then set.. Can you elaborate? If I run QEMU, hosting Xen, hosting Linux, and the virtio device is provided by QEMU, then how does Xen set the bit? Similarly, how would Xen set the bit for a real physical device? --Andy