-----Original Message-----
From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Nitin Gote
Sent: Thursday, July 11, 2024 9:32 AM
To: Wilson, Chris P <chris.p.wilson@xxxxxxxxx>; tursulin@xxxxxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx; Shyti, Andi <andi.shyti@xxxxxxxxx>; Das, Nirmoy <nirmoy.das@xxxxxxxxx>; janusz.krzysztofik@xxxxxxxxxxxxxxx; Gote, Nitin R <nitin.r.gote@xxxxxxxxx>; Chris Wilson <chris.p.wilson@xxxxxxxxxxxxxxx>; stable@xxxxxxxxxxxxxxx
Subject: [PATCH v3] drm/i915/gt: Do not consider preemption during execlists_dequeue for gen8
>
> We're seeing a GPU HANG issue on a CHV platform, which was caused by
> bac24f59f454 ("drm/i915/execlists: Enable coarse preemption boundaries for gen8").
>
> Gen8 platform has only timeslice and doesn't support a preemption mechanism
> as engines do not have a preemption timer and doesn't send an irq if the
> preemption timeout expires.
That seems to mean the original can_preempt function was inaccurately built,
so fixing it here makes the most sense to me, especially if it's causing problems.
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@xxxxxxxxx>
-Jonathan Cavitt
> So, add a fix to not consider preemption
> during dequeuing for gen8 platforms.
>
> v2: Simplify can_preempt() function (Tvrtko Ursulin)
>
> v3:
> - Inside need_preempt(), condition of can_preempt() is not required
> as simplified can_preempt() is enough. (Chris Wilson)
>
> Fixes: bac24f59f454 ("drm/i915/execlists: Enable coarse preemption boundaries for gen8")
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11396
> Suggested-by: Andi Shyti <andi.shyti@xxxxxxxxx>
> Signed-off-by: Nitin Gote <nitin.r.gote@xxxxxxxxx>
> Cc: Chris Wilson <chris.p.wilson@xxxxxxxxxxxxxxx>
> CC: <stable@xxxxxxxxxxxxxxx> # v5.2+
> ---
> drivers/gpu/drm/i915/gt/intel_execlists_submission.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index 21829439e686..72090f52fb85 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -3315,11 +3315,7 @@ static void remove_from_engine(struct i915_request *rq)
>
> static bool can_preempt(struct intel_engine_cs *engine)
> {
> - if (GRAPHICS_VER(engine->i915) > 8)
> - return true;
> -
> - /* GPGPU on bdw requires extra w/a; not implemented */
> - return engine->class != RENDER_CLASS;
> + return GRAPHICS_VER(engine->i915) > 8;
> }
>
> static void kick_execlists(const struct i915_request *rq, int prio)
> --
> 2.25.1
>
>
