From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39581) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZHsO0-0004Je-Rn for qemu-devel@nongnu.org; Wed, 22 Jul 2015 07:40:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZHsNx-0004CS-1q for qemu-devel@nongnu.org; Wed, 22 Jul 2015 07:40:32 -0400 Received: from mail-wi0-x230.google.com ([2a00:1450:400c:c05::230]:33417) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZHsNw-0004Bp-Qz for qemu-devel@nongnu.org; Wed, 22 Jul 2015 07:40:28 -0400 Received: by wicmv11 with SMTP id mv11so77616722wic.0 for ; Wed, 22 Jul 2015 04:40:27 -0700 (PDT) Sender: Paolo Bonzini References: <1437544792-3949-1-git-send-email-jasowang@redhat.com> <1437544792-3949-3-git-send-email-jasowang@redhat.com> <20150722093145.GD12010@redhat.com> <20150722131342-mutt-send-email-mst@redhat.com> From: Paolo Bonzini Message-ID: <55AF8129.50105@redhat.com> Date: Wed, 22 Jul 2015 13:40:25 +0200 MIME-Version: 1.0 In-Reply-To: <20150722131342-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH V3 2/3] virtio-blk: fail get_features when both scsi and 1.0 were set List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , "Daniel P. Berrange" Cc: cornelia.huck@de.ibm.com, Jason Wang , qemu-devel@nongnu.org On 22/07/2015 12:19, Michael S. Tsirkin wrote: > > > SCSI passthrough was no longer supported in virtio 1.0, so this patch > > > fail the get_features() when both 1.0 and scsi is set. And also only > > > advertise VIRTIO_BLK_F_SCSI for legacy virtio-blk device. > > > > Why is SCSI passthrough support not available in virtio 1.0 ? This > > will cause a regression for any users of that as & when QEMU changes > > to use virtio 1.0 by default. Can we not fix this regression instead. > > If we wanted to, we might be able to fix this but not for 2.4: we'd have > to extend the spec and guest drivers, in some way TBD. > > Paolo would be best placed to answer whether this feature is desirable > in the future, I think the argument made when the spec was written was that > the feature is not widely used, and virtio scsi is available as > a replacement for people who need it. No, the feature is not desirable in the future. There is no reason really not to use virtio-scsi passthrough instead, since virtio-scsi has been out for about 3 years now and is stable. In addition, the implementation would either not be compatible with virtio 0.9, or would be different from everything else in the spec because it requires a particular framing for the buffers. Paolo