[PATCH v2 0/4] gpu: nova-core: gsp: add locking to Cmdq

[Eliot Courtney]

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 ("sync") and commands that don't
("async"). For sync commands 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 sync 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.
SyncCommand and AsyncCommand, 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 send a sync or async
   command.
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>
---
Changes in v2:
- Rebase on drm-rust-next
- Link to v1: https://lore.kernel.org/r/20260225-cmdq-locking-v1-0-bbf6b4156706@xxxxxxxxxx

---
Eliot Courtney (4):
      gpu: nova-core: gsp: fix stale doc comments on command queue methods
      gpu: nova-core: gsp: add sync and async command queue API to `Cmdq`
      gpu: nova-core: gsp: make `Cmdq` a pinned type
      gpu: nova-core: gsp: add mutex locking to Cmdq

 drivers/gpu/nova-core/gsp.rs           |   5 +-
 drivers/gpu/nova-core/gsp/boot.rs      |  13 +-
 drivers/gpu/nova-core/gsp/cmdq.rs      | 246 +++++++++++++++++++++------------
 drivers/gpu/nova-core/gsp/commands.rs  |  23 ++-
 drivers/gpu/nova-core/gsp/sequencer.rs |   2 +-
 5 files changed, 183 insertions(+), 106 deletions(-)
---
base-commit: 4a49fe23e357b48845e31fe9c28a802c05458198
change-id: 20260225-cmdq-locking-d32928a2c2cf
prerequisite-message-id: <20260226-cmdq-continuation-v3-0-572ab9916766@xxxxxxxxxx>
prerequisite-patch-id: fd45bc5b8eda5e2b54a052dddb1a1c363107f0a7
prerequisite-patch-id: d0f59ef489346e978a222755f9fb42dfe7af19e5
prerequisite-patch-id: 8844970d0e387488c70979a73732579ba174b46c
prerequisite-patch-id: e138a94ed48fa8d50d5ed1eb36524f98923ed478
prerequisite-patch-id: 4599a5e90d6665fa3acb7d4045de5d378ac28b4d
prerequisite-patch-id: 30ed64c398e541d6efbcb2e46ed9a9e6cf953f4f
prerequisite-patch-id: 9a965e9f29c8680c0b554e656ff8e9a1bfc67280
prerequisite-patch-id: d8cccc3dfb070f304805fc7e0f24121809b4b300
prerequisite-patch-id: c0a73dfd1fb630ab02486f0180b90f8fe850b4dc

Best regards,
-- 
Eliot Courtney <ecourtney@xxxxxxxxxx>