From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [virtio-dev] Re: [Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net Date: Wed, 20 Jun 2018 11:53:59 +0200 Message-ID: <20180620115359.1a3bf6fb.cohuck@redhat.com> 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 Cc: Alexander Duyck , virtio-dev@lists.oasis-open.org, Jiri Pirko , konrad.wilk@oracle.com, Jakub Kicinski , "Samudrala, Sridhar" , qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Siwei Liu , Venu Busireddy , Netdev , boris.ostrovsky@oracle.com, aaron.f.brown@intel.com, Joao Martins To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20180619233001-mutt-send-email-mst@kernel.org> 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-Id: netdev.vger.kernel.org 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).