Re: [PATCH 2/2] drm/i915/guc: Don't unblock a banned context

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] drm/i915/guc: context_cant_unblock() misses exiting contexts
  on unblock
--

commit f3c1b0cc59baf35aaa07862b720ef5529fd5baed
Author: Javier MV <javiermv@duck.com>

drm/i915/guc: Don't unblock a banned context

This commit adds an intel_context_is_banned() check to
context_cant_unblock() so that guc_context_unblock() does not re-enable
scheduling on a banned context after the schedule-disable done handler
clears SCHED_STATE_BANNED.

Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15301

> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 555ca8fdf64af..eb1d010ed3dcc 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -3182,7 +3182,12 @@ static bool context_cant_unblock(struct intel_context *ce)
>  {
>  	lockdep_assert_held(&ce->guc_state.lock);
>  
> +	/*
> +	 * SCHED_STATE_BANNED alone isn't enough: the sched disable done
> +	 * handler clears it.
> +	 */
>  	return (ce->guc_state.sched_state & SCHED_STATE_NO_UNBLOCK) ||
> +		intel_context_is_banned(ce) ||
>  		context_guc_id_invalid(ce) ||
>  		!ctx_id_mapped(ce_to_guc(ce), ce->guc_id.id) ||
>  		!intel_context_is_pinned(ce);

[Severity: Medium]
Should this check !intel_context_is_schedulable(ce) instead of
intel_context_is_banned(ce)?

intel_context_revoke() sets CONTEXT_EXITING (not CONTEXT_BANNED) via
intel_context_set_exiting() before calling guc_context_revoke(), which
then takes the same SCHED_STATE_BANNED path as a banned context.  If
intel_context_revoke() (for example on context close or process exit for
a non-persistent context) races with guc_context_cancel_request() while
the block schedule-disable is pending, intel_guc_sched_done_process_msg()
clears SCHED_STATE_BANNED and cancels the inflight requests with -EIO.

When guc_context_cancel_request() resumes, guc_reset_state() sees
!intel_context_is_schedulable(ce) and returns early without scrubbing the
LRC or advancing the ring head, and then guc_context_unblock() re-enables
scheduling in GuC for the revoked context with an un-scrubbed ring and
already-completed requests.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261110122534.12989-1-javiermv@gmail.com?part=2