RE: [PATCH v2 4/4] Add support for MSI-X vectors configuration for PCI VFs

[Parav Pandit <parav@nvidia.com>]

> From: Jason Wang <jasowang@redhat.com>
> Sent: Thursday, January 27, 2022 9:06 AM

[...]

> 
> And I think it's better to explicit split the commands then we can have
> dedicated commands for MSI instead of trying to mix all SRIOV related
> attributes into the same command.

It is not mixed. Its clubbed together so that driver-device communication can be minimal and still flexible.

For example in [1] it has, command like,
ip link add vx0 type vxlan id 100 local 1.1.1.1 remote 2.2.2.2 dev eth0 dstport 4789

it would be inefficient do it as,
$ ip link add vx0 type vxlan id 100
$ ip link vx0 local 1.1.1.1 
$ ip link vx0 remote 2.2.2.2 
$ ip link vx0 dev eth0 
$ ip link vx0 dstport 4789

[1] https://developers.redhat.com/blog/2018/10/22/introduction-to-linux-interfaces-for-virtual-networking#macvlan

Similarly, we prefer the ability and flexibility to set more fields in one command.

> I think it's better to have a dedicated command to set the msix_vectors, then
> there's no need for the attrs_mask.
> 
Main design principle in having attr_mask is to avoid issuing multiple commands for related/adjacent attributes.
Lesser the number of commands serviced, more efficient the overall system is.
Hence the attribute mask gives the flexibility to set one or more.