Re: [PATCH v3 0/5] gpu: nova-core: gsp: add locking to Cmdq

["Alexandre Courbot" <acourbot@nvidia.com>]

On Wed Mar 4, 2026 at 11:46 AM JST, Eliot Courtney wrote:
> Add locking to Cmdq. This is required e.g. for unloading the driver,
> which needs to send the UnloadingGuestDriver via the command queue
> on unbind which may be on a different thread.
>
> We have commands that need a reply and commands that don't. For
> commands with a reply we want to make sure that they don't get
> the reply of a different command back. The approach this patch series
> takes is by making those commands block until they get a response. For
> now this should be ok, and we expect GSP to be fast anyway.
>
> To do this, we need to know which commands expect a reply and which
> don't. John's existing series[1] adds IS_ASYNC which solves part of the
> problem, but we need to know a bit more. So instead, add an
> associated type called Reply which tells us what the reply is.
>
> An alternative would be to define traits inheriting CommandToGsp, e.g.
> CommandWithReply and CommandWithoutReply, instead of using the
> associated type. I implemented the associated type version because it
> feels more compositional rather than inherity so seemed a bit better
> to me. But both of these approaches work and are fine, IMO.

The associated type seems to work just fine. I was wondering whether we
could mess with it by using other types that do not implement
`MessageFromGsp`, but in that case we cannot call any of the
`send_command` methods so this approach looks good to me.