On 1/12/2022 21:59, Matthew Brost wrote:

Realized that the GuC multi-lrc fini breadcrumb emit code is very delicate as the math this code does relies on functions it calls to emit a certain number of DWs. Add a few GEM_BUG_ONs to assert the math is correct.

Signed-off-by: Matthew Brost matthew.brost@intel.com

Looks good. There was a checkpatch warning about blank lines. With that fixed: Reviewed-by: John Harrison John.C.Harrison@Intel.com

---

.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 32 +++++++++++++++---- 1 file changed, 26 insertions(+), 6 deletions(-)

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 3ae92260f8224..d562d85f96871 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -4493,27 +4493,31 @@ static inline bool skip_handshake(struct i915_request *rq) return test_bit(I915_FENCE_FLAG_SKIP_PARALLEL, &rq->fence.flags); }

+#define NON_SKIP_LEN 6 static u32 * emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq, u32 *cs) { struct intel_context *ce = rq->context;

• __maybe_unused u32 *before_fini_breadcrumb_user_interrupt_cs;

• __maybe_unused u32 *start_fini_breadcrumb_cs = cs;

  GEM_BUG_ON(!intel_context_is_parent(ce));

  if (unlikely(skip_handshake(rq))) { /*

  • NOP everything in __emit_fini_breadcrumb_parent_no_preempt_mid_batch,

•  * the -6 comes from the length of the emits below.
  

•  * the NON_SKIP_LEN comes from the length of the emits below.
  

  */ memset(cs, 0, sizeof(u32) *

•        (ce->engine->emit_fini_breadcrumb_dw - 6));
  

• cs += ce->engine->emit_fini_breadcrumb_dw - 6;
  

•        (ce->engine->emit_fini_breadcrumb_dw - NON_SKIP_LEN));
  

• cs += ce->engine->emit_fini_breadcrumb_dw - NON_SKIP_LEN;
  

  } else { cs = __emit_fini_breadcrumb_parent_no_preempt_mid_batch(rq, cs); }

  /* Emit fini breadcrumb */

• before_fini_breadcrumb_user_interrupt_cs = cs; cs = gen8_emit_ggtt_write(cs, rq->fence.seqno, i915_request_active_timeline(rq)->hwsp_offset,

@@ -4523,6 +4527,12 @@ emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq, *cs++ = MI_USER_INTERRUPT; *cs++ = MI_NOOP;

• /* Ensure our math for skip + emit is correct */

• GEM_BUG_ON(before_fini_breadcrumb_user_interrupt_cs + NON_SKIP_LEN !=

•    cs);
  

• GEM_BUG_ON(start_fini_breadcrumb_cs +

•    ce->engine->emit_fini_breadcrumb_dw != cs);
  

• rq->tail = intel_ring_offset(rq, cs);

  return cs;

@@ -4565,22 +4575,25 @@ emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq, u32 *cs) { struct intel_context *ce = rq->context;

• __maybe_unused u32 *before_fini_breadcrumb_user_interrupt_cs;

• __maybe_unused u32 *start_fini_breadcrumb_cs = cs;

  GEM_BUG_ON(!intel_context_is_child(ce));

  if (unlikely(skip_handshake(rq))) { /*

  • NOP everything in __emit_fini_breadcrumb_child_no_preempt_mid_batch,

•  * the -6 comes from the length of the emits below.
  

•  * the NON_SKIP_LEN comes from the length of the emits below.
  

  */ memset(cs, 0, sizeof(u32) *

•        (ce->engine->emit_fini_breadcrumb_dw - 6));
  

• cs += ce->engine->emit_fini_breadcrumb_dw - 6;
  

•        (ce->engine->emit_fini_breadcrumb_dw - NON_SKIP_LEN));
  

• cs += ce->engine->emit_fini_breadcrumb_dw - NON_SKIP_LEN;
  

  } else { cs = __emit_fini_breadcrumb_child_no_preempt_mid_batch(rq, cs); }

  /* Emit fini breadcrumb */

• before_fini_breadcrumb_user_interrupt_cs = cs; cs = gen8_emit_ggtt_write(cs, rq->fence.seqno, i915_request_active_timeline(rq)->hwsp_offset,

@@ -4590,10 +4603,17 @@ emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq, *cs++ = MI_USER_INTERRUPT; *cs++ = MI_NOOP;

• /* Ensure our math for skip + emit is correct */

• GEM_BUG_ON(before_fini_breadcrumb_user_interrupt_cs + NON_SKIP_LEN !=

•    cs);
  

• GEM_BUG_ON(start_fini_breadcrumb_cs +

•    ce->engine->emit_fini_breadcrumb_dw != cs);
  

• rq->tail = intel_ring_offset(rq, cs);

  return cs; }

+#undef NON_SKIP_LEN

static struct intel_context * guc_create_virtual(struct intel_engine_cs **siblings, unsigned int count,