Hi Alex, Silly questions on the background: > From: Alex Williamson <alex.williamson@xxxxxxxxxx> > Sent: Wednesday, February 5, 2020 7:06 AM > Subject: [RFC PATCH 0/7] vfio/pci: SR-IOV support > > There seems to be an ongoing desire to use userspace, vfio-based > drivers for both SR-IOV PF and VF devices. Is this series to make PF be bound-able to vfio-pci even SR-IOV is enabled on such PFs? If yes, is it allowed to assign PF to a VM? or it can only be used by userspace applications like DPDK? > The fundamental issue > with this concept is that the VF is not fully independent of the PF > driver. Minimally the PF driver might be able to deny service to the > VF, VF data paths might be dependent on the state of the PF device, > or the PF my have some degree of ability to inspect or manipulate the > VF data. It therefore would seem irresponsible to unleash VFs onto > the system, managed by a user owned PF. > > We address this in a few ways in this series. First, we can use a bus > notifier and the driver_override facility to make sure VFs are bound > to the vfio-pci driver by default. This should eliminate the chance > that a VF is accidentally bound and used by host drivers. We don't > however remove the ability for a host admin to change this override. > > The next issue we need to address is how we let userspace drivers > opt-in to this participation with the PF driver. We do not want an > admin to be able to unwittingly assign one of these VFs to a tenant > that isn't working in collaboration with the PF driver. We could use > IOMMU grouping, but this seems to push too far towards tightly coupled > PF and VF drivers. This series introduces a "VF token", implemented > as a UUID, as a shared secret between PF and VF drivers. The token > needs to be set by the PF driver and used as part of the device > matching by the VF driver. Provisions in the code also account for > restarting the PF driver with active VF drivers, requiring the PF to > use the current token to re-gain access to the PF. How about the scenario in which PF driver is vfio-based userspace driver but VF drivers are mixed. This means not all VFs are bound to vfio-based userspace driver. Is it also supported here? :-) Regards, Yi Liu
