Re: vPASID capability for VF

[Jason Gunthorpe]

On Tue, May 09, 2023 at 08:34:53AM +0000, Tian, Kevin wrote:
> According to PCIe spec (7.8.9 PASID Extended Capability Structure):
> 
>   The PASID configuration of the single non-VF Function representing
>   the device is also used by all VFs in the device. A PF is permitted
>   to implement the PASID capability, but VFs must not implement it.
> 
> To enable PASID on VF then one open is where to locate the PASID
> capability in VF's vconfig space. vfio-pci doesn't know which offset
> may contain VF specific config registers. Finding such offset must
> come from a device specific knowledge.

Why? Can't vfio probe the cap tree and just find a gap to insert a new
cap? We already mangle the cap list, I'm not sure I see what
the problem is?

Jason