Re: [PATCH v5 0/5] gpu: nova-core: gsp: add locking to Cmdq

[Alexandre Courbot]

On Wed Mar 18, 2026 at 1:07 PM 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.
>
> In summary, this patch series has three steps:
> 1. Add the type infrastructure to know what replies are expected for a
>    command and update each caller to explicitly wait for the reply or
>    not.
> 2. Make Cmdq pinned so we can use Mutex
> 3. Add a Mutex to protect Cmdq by moving the relevant state to an
>    inner struct.
>
> [1]: https://lore.kernel.org/all/20260211000451.192109-1-jhubbard@xxxxxxxxxx/
>
> Signed-off-by: Eliot Courtney <ecourtney@xxxxxxxxxx>

Merged into drm-rust-next, thanks!