Re: [RFC PATCH 1/5] nvme-pci: add function nvme_submit_vf_cmd to issue admin commands for VF driver.

[Christoph Hellwig]

On Tue, Dec 06, 2022 at 11:22:33AM -0400, Jason Gunthorpe wrote:
> > controlled functions (which could very well be, and in some designs
> > are, additional PFs and not VFs) by controlling function.  
> 
> In principle PF vs VF doesn't matter much - the question is really TLP
> labeling. If the spec says RID A is the controlling RID and RID B is
> the guest RID, then it doesn't matter if they have a PF/VF
> relationship or PF/PF relationship.

Yes.  Or in fact if you use PASIDs inside a single function.

> We have locking issues in Linux SW connecting different SW drivers for
> things that are not a PF/VF relationship, but perhaps that can be
> solved.

And I think the only reasonable answer is that the entire workflow
must be 100% managed from the controlling function, and the controlled
function is just around for a ride, with the controlling function
enabling/disabling it as needed without ever interacting with software
that directly deals with the controlled function.