On 9/30/25 6:39 PM, Alexandre Courbot wrote: > On Wed Oct 1, 2025 at 10:26 AM JST, John Hubbard wrote: >> On 9/30/25 5:26 PM, Alexandre Courbot wrote: >>> On Wed Oct 1, 2025 at 7:07 AM JST, John Hubbard wrote: >>>> Post-Kangrejos, the approach for NovaCore + VFIO has changed a bit: the >>>> idea now is that VFIO drivers, for NVIDIA GPUs that are supported by >>>> NovaCore, should bind directly to the GPU's VFs. (An earlier idea was to >>>> let NovaCore bind to the VFs, and then have NovaCore call into the upper >>>> (VFIO) module via Aux Bus, but this turns out to be awkward and is no >>>> longer in favor.) So, in order to support that: >>>> >>>> Nova-core must only bind to Physical Functions (PFs) and regular PCI >>>> devices, not to Virtual Functions (VFs) created through SR-IOV. >>> >>> Naive question: will guests also see the passed-through VF as a VF? If >>> so, wouldn't this change also prevents guests from using Nova? >> >> I'm also new to this area. I would expect that guests *must* see >> these as PFs, otherwise...nothing makes any sense. > > But if the guest sees the passed-through VF as a PF, won't it try to > do things it is not supposed to do like loading the GSP firmware (which > is managed by the host)?
Yes. A non-paravirtualized guest will attempt to behave just like a bare metal driver would behave. It's the job of the various layers of virtualization to intercept and modify such things appropriately. Looking ahead: if the VFIO experts come back and tell us that guests see these as VFs, then there is still a way forward, because we talked about loading nova-core with a "vfio_mode" kernel module parameter. So then it becomes "if vfio_mode, then skip VFs". thanks, -- John Hubbard
