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

[Dong, Eddie]

> 
> If following the direction having controlling function to explicitly provide
> services then all those doorbells should be deprecated and instead we want
> explicit communications between VF driver and PF driver.

Hardware mechanism of communication (door bell here) can be used to 
support broader scenario when VF driver and PF driver run in 2 different
OS kernels (when the VF is assigned to a VM).

> 
> From userspace driver p.o.v. the VFIO uAPI is kind of a device programming
> interface. Here we just present everything related to the controlled device
> itself (including the state management) via a centralized portal though in the
> kernel there might be linkage out of VFIO to reach the controlling driver. kind
> of a sw doorbell. 😊

Yes.
And sw doorbell is more efficient than hardware doorbell 😊 .