-----Original Message----- From: Tvrtko Ursulin tursulin@ursulin.net Sent: Wednesday, July 10, 2024 4:22 PM To: Gote, Nitin R nitin.r.gote@intel.com; intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org; Shyti, Andi andi.shyti@intel.com; chris.p.wilson@linux.intel.com; Das, Nirmoy nirmoy.das@intel.com; janusz.krzysztofik@linux.intel.com; stable@vger.kernel.org Subject: Re: [PATCH] drm/i915/gt: Do not consider preemption during execlists_dequeue for gen8
On 09/07/2024 15:02, Tvrtko Ursulin wrote:
On 09/07/2024 13:53, Nitin Gote wrote:
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. So, add a fix to not consider preemption during dequeuing for gen8 platforms.
Also move can_preemt() above need_preempt() function to resolve implicit declaration of function ‘can_preempt' error and make can_preempt() function param as const to resolve error: passing argument 1 of ‘can_preempt’ discards ‘const’ qualifier from the pointer
target type.
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@intel.com Signed-off-by: Nitin Gote nitin.r.gote@intel.com Cc: Chris Wilson chris.p.wilson@linux.intel.com CC: stable@vger.kernel.org # v5.2+
.../drm/i915/gt/intel_execlists_submission.c | 24 ++++++++++++------- 1 file changed, 15 insertions(+), 9 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..30631cc690f2 100644 --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c @@ -294,11 +294,26 @@ static int virtual_prio(const struct intel_engine_execlists *el) return rb ? rb_entry(rb, struct ve_node, rb)->prio : INT_MIN; } +static bool can_preempt(const struct intel_engine_cs *engine) { + if (GRAPHICS_VER(engine->i915) > 8) + return true;
+ if (IS_CHERRYVIEW(engine->i915) || IS_BROADWELL(engine->i915)) + return false;
+ /* GPGPU on bdw requires extra w/a; not implemented */ + return engine->class != RENDER_CLASS;
Aren't BDW and CHV the only Gen8 platforms, in which case this function can be simplifies as:
... { return GRAPHICS_VER(engine->i915) > 8; }
?
+}
Yes. I will simply this function.
static bool need_preempt(const struct intel_engine_cs *engine, const struct i915_request *rq) { int last_prio; + if ((GRAPHICS_VER(engine->i915) <= 8) && can_preempt(engine))
The GRAPHICS_VER check here looks redundant with the one inside can_preempt().
True. I will update the condition.
One more thing - I think gen8_emit_bb_start() becomes dead code after this and can be removed.
I think gen8_emit_bb_start() still require for graphics version < 12 as it is used in else part of if (GRAPHICS_VER_FULL(engine->i915) >= IP_VER(12, 55)) condition. So, it will not be dead code.
Thanks and Regards, Nitin
Regards,
Tvrtko
+ return false;
if (!intel_engine_has_semaphores(engine)) return false; @@ -3313,15 +3328,6 @@ static void remove_from_engine(struct i915_request *rq) i915_request_notify_execute_cb_imm(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; -}
static void kick_execlists(const struct i915_request *rq, int prio) { struct intel_engine_cs *engine = rq->engine;