Re: [virtio-comment] RE: [PATCH v2 1/2] transport-pci: Introduce legacy registers access commands

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, May 18, 2023 at 03:42:19PM -0400, Michael S. Tsirkin wrote:
> > > Does this sound like a reasonable
> > > compromize to you?
> > 
> > Splitting proposed one command to two commands,
> > 1. one for accessing legacy common config
> > 2. second for accessing legacy device specific config 
> > 
> > seems fine to me as below.
> > 
> > So we will have total 5 commands (instead of 3).
> > 
> > 1. legacy common config read
> > 2. legacy common config write
> > 
> > 3. legacy device config read
> > 4. legacy device config write
> > 5. query device notification area
> > 
> > #1 and #3 same cmd signature but different opcode.
> > #2 and #4 same cmd signature but different opcode.
> > 
> 
> Sounds reasonable. Jason?
> 
> notification thing needs more thought I feel though.
> It feels weirdly bolted on, but I can't put my finger
> on what's wrong exactly yet. Will think it over.


So with a fresh mind, at least three things:

1. given driver attaches to the PF, it should be possible to forward
   notifications there, as opposed to individual VFs.  NumVFs is 16 bit so
   it will fit in a 32 bit write together with VQ index.

2. It should be possible to send notifications through an admin command too,
   otherwise admin commands are an incomplete set of functionality.
   
3. I feel using a capability to describe legacy notification
   area would be better just because we already have a
   structure for this. make it an express capability if you like.


-- 
MST