From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51527) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fVZoa-0001EU-4Z for qemu-devel@nongnu.org; Wed, 20 Jun 2018 05:54:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fVZoV-0001tO-6A for qemu-devel@nongnu.org; Wed, 20 Jun 2018 05:54:12 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:48308 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 1fVZoV-0001tE-0h for qemu-devel@nongnu.org; Wed, 20 Jun 2018 05:54:07 -0400 Date: Wed, 20 Jun 2018 11:53:59 +0200 From: Cornelia Huck Message-ID: <20180620115359.1a3bf6fb.cohuck@redhat.com> In-Reply-To: <20180619233001-mutt-send-email-mst@kernel.org> References: <20180612051432-mutt-send-email-mst@kernel.org> <23fc4aa4-ec41-d6e2-3354-10cbfc13b7ec@intel.com> <20180612142557-mutt-send-email-mst@kernel.org> <20180614120231.0a72bd5f.cohuck@redhat.com> <20180615134815.6613620e.cohuck@redhat.com> <20180619125453.2d2dfb2d.cohuck@redhat.com> <20180619233001-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Siwei Liu , "Samudrala, Sridhar" , Alexander Duyck , virtio-dev@lists.oasis-open.org, aaron.f.brown@intel.com, Jiri Pirko , Jakub Kicinski , Netdev , qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, Joao Martins , Venu Busireddy , vijay.balakrishna@oracle.com On Tue, 19 Jun 2018 23:32:06 +0300 "Michael S. Tsirkin" wrote: > On Tue, Jun 19, 2018 at 12:54:53PM +0200, Cornelia Huck wrote: > > Sorry about dragging mainframes into this, but this will only work for > > homogenous device coupling, not for heterogenous. Consider my vfio-pci > > + virtio-net-ccw example again: The guest cannot find out that the two > > belong together by checking some group ID, it has to either use the MAC > > or some needs-to-be-architectured property. > > > > Alternatively, we could propose that mechanism as pci-only, which means > > we can rely on mechanisms that won't necessarily work on non-pci > > transports. (FWIW, I don't see a use case for using vfio-ccw to pass > > through a network card anytime in the near future, due to the nature of > > network cards currently in use on s390.) > > That's what it boils down to, yes. If there's need to have this for > non-pci devices, then we should put it in config space. > Cornelia, what do you think? > I think the only really useful config on s390 is the vfio-pci network card coupled with a virtio-net-ccw device: Using an s390 network card via vfio-ccw is out due to the nature of the s390 network cards, and virtio-ccw is the default transport (virtio-pci is not supported on any enterprise distro AFAIK). For this, having a uuid in the config space could work (vfio-pci devices have a config space by virtue of being pci devices, and virtio-net-ccw devices have a config space by virtue of being virtio devices -- ccw devices usually don't have that concept).