On Fri, Mar 16, 2018 at 09:40:34AM -0700, Alexander Duyck wrote: > On Fri, Mar 16, 2018 at 9:34 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > On Thu, Mar 15, 2018 at 11:42:41AM -0700, Alexander Duyck wrote: > >> From: Alexander Duyck <alexander.h.duyck@xxxxxxxxx> > >> > >> Hardware-realized virtio_pci devices can implement SR-IOV, so this > >> patch enables its use. The device in question is an upcoming Intel > >> NIC that implements both a virtio_net PF and virtio_net VFs. These > >> are hardware realizations of what has been up to now been a software > >> interface. > >> > >> The device in question has the following 4-part PCI IDs: > >> > >> PF: vendor: 1af4 device: 1041 subvendor: 8086 subdevice: 15fe > >> VF: vendor: 1af4 device: 1041 subvendor: 8086 subdevice: 05fe > >> > >> The patch currently needs no check for device ID, because the callback > >> will never be made for devices that do not assert the capability or > >> when run on a platform incapable of SR-IOV. > >> > >> One reason for this patch is because the hardware requires the > >> vendor ID of a VF to be the same as the vendor ID of the PF that > >> created it. So it seemed logical to simply have a fully-functioning > >> virtio_net PF create the VFs. This patch makes that possible. > >> > >> Reviewed-by: Christoph Hellwig <hch@xxxxxx> > >> Signed-off-by: Mark Rustad <mark.d.rustad@xxxxxxxxx> > >> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx> > > > > So if and when virtio PFs can manage the VFs, then we can > > add a feature bit for that? > > Seems reasonable. > > Yes. If nothing else you may not even need a feature bit depending on > how things go. OTOH if the interface is changed in an incompatible way, and old Linux will attempt to drive the new device since there is no check. I think we should add a feature bit right away. > One of the reasons why Mark called out the > subvendor/subdevice was because that might be able to be used to > identify the specific hardware that is providing the SR-IOV feature so > in the future if it is added to virtio itself then you could exclude > devices like this by just limiting things based on subvendor/subdevice > IDs. > > > Also, I am guessing that hardware implementations will want > > to add things like stong memory barriers - I guess we > > will add new feature bits for that too down the road? > > That piece I don't have visibility into at this time. Perhaps Dan > might have more visibility into future plans on what this might need. > > Thanks. > > - Alex
