From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42251) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fdolH-0000SU-4x for qemu-devel@nongnu.org; Thu, 12 Jul 2018 23:28:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fdolC-0008Bv-4V for qemu-devel@nongnu.org; Thu, 12 Jul 2018 23:28:51 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:34318 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fdolB-0008At-Up for qemu-devel@nongnu.org; Thu, 12 Jul 2018 23:28:46 -0400 Date: Fri, 13 Jul 2018 06:28:39 +0300 From: "Michael S. Tsirkin" Message-ID: <20180713062755-mutt-send-email-mst@kernel.org> References: <9136094e-a510-4201-7c71-d1c49226fa5f@oracle.com> <20180710045101-mutt-send-email-mst@kernel.org> <20180711115344.633eba9e.cohuck@redhat.com> <20180712133121.3b5f2bae.cohuck@redhat.com> <20180712235500-mutt-send-email-mst@kernel.org> <77823ff9-a02a-808b-e919-b4950a64ae3c@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <77823ff9-a02a-808b-e919-b4950a64ae3c@intel.com> Subject: Re: [Qemu-devel] [virtio-dev] Re: [PATCH v3 0/3] Use of unique identifier for pairing virtio and passthrough devices... List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Samudrala, Sridhar" Cc: Siwei Liu , Cornelia Huck , si-wei liu , Roman Kagan , Venu Busireddy , Marcel Apfelbaum , virtio-dev@lists.oasis-open.org, qemu-devel@nongnu.org, Alexander Duyck , Netdev On Thu, Jul 12, 2018 at 09:20:41PM -0400, Samudrala, Sridhar wrote: > On 7/12/2018 6:19 PM, Siwei Liu wrote: > > On Thu, Jul 12, 2018 at 2:00 PM, Michael S. Tsirkin wrote: > > > On Thu, Jul 12, 2018 at 01:52:53PM -0700, Siwei Liu wrote: > > > > The definition is incomplete due to lack of spec. There's no "host" > > > > part defined yet in the host-guest interface. If match by MAC is an > > > > interface, the same must be done on the host(device) side as well, > > > > which has been agreed not the way to go. However, I don't think that's > > > > what the author intends to do by interpreting his QEMU patch - it > > > > missed the other parts as well, such as the feature negotiation and > > > > how it interacts with the paired device. > > > > > > > > What I said is that match by MAC is just a guest implementation that > > > > one can change at any time. We now have the group ID on QEMU, why > > > > still sticking to matching by MAC? It shoulnd't be a host-guest > > > > interface in the first place anyway. > > > I think that match by MAC is a simple portable way to match devices. > > > E.g. it will work seamlessly with niche things like zPCI. However > > That's a good point. I'm not sure if it's a valid assumption that zPCI > > should always use the same MAC address as that of virtio. Someone > > who's more familiar with the use case may decide and work on that. It > > means VFIO device has to take in the MAC address as an identifier to > > the "-device vfio-pci,.." QEMU option. I think there's no point to > > match device using group ID in QEMU while using MAC in the guest. > > Based on that assumption, I'd go with making VIRTIO_NET_F_STANDBY to > > match device based on group ID, while someone may come up with another > > feature bit later, say VIRTIO_NET_F_STANDBY_BY_MAC when its QEMU > > support is available. Would it make sense? > > VIRTIO_NET_F_STANDBY as defined in the guest virtio_net driver supports match > by MAC address. I think we should add support for this feature bit in QEMU. > If submitting a patch to update the spec is a pre-requisite to add this > feature bit to QEMU, i can do that. It's not strictly a prerequisite but we need it in spec all the same, so pls do that. > As far as i understand, group id patches to QEMU are still under review. > Matching by group ID can be another feature bit that could support matching > by group id as well as MAC. > > > > -Siwei > > > > > there are other niche use-cases that aren't addressed by match by MAC > > > such as PF pass-through as a primary, and the pci bridge trick addresses > > > that at cost of some portability. > > > > > > So I see no issues supporting both mechanisms, but others on the TC > > > might feel differently. > > > > > > -- > > > MST