Re: [PATCH v3] drm/i915: Refactor tests for validity of RING_TAIL

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Whilst I like having the assertions clearly visible in the code, they
> are quite repetitious! As we find new limits we want to incorporate into
> the set of assertions, it make sense to refactor them to a common
> routine.
>
> v2: Add a guc holdout.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

> ---
>  drivers/gpu/drm/i915/i915_guc_submission.c |  2 +-
>  drivers/gpu/drm/i915/intel_lrc.c           | 12 ++++--------
>  drivers/gpu/drm/i915/intel_ringbuffer.c    |  9 +++------
>  drivers/gpu/drm/i915/intel_ringbuffer.h    | 11 +++++++++++
>  4 files changed, 19 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index 991e76e10f82..6193ad7edcf4 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -481,7 +481,7 @@ static void guc_wq_item_append(struct i915_guc_client *client,
>  
>  	/* The GuC firmware wants the tail index in QWords, not bytes */
>  	tail = rq->tail;
> -	GEM_BUG_ON(tail & 7);
> +	assert_ring_tail_valid(rq->ring, rq->tail);
>  	tail >>= 3;
>  	GEM_BUG_ON(tail > WQ_RING_TAIL_MAX);
>  
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 39cb84a5d4e4..b0c3a029b592 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -326,8 +326,7 @@ static u64 execlists_update_context(struct drm_i915_gem_request *rq)
>  		rq->ctx->ppgtt ?: rq->i915->mm.aliasing_ppgtt;
>  	u32 *reg_state = ce->lrc_reg_state;
>  
> -	GEM_BUG_ON(!IS_ALIGNED(rq->tail, 8));
> -	GEM_BUG_ON(rq->tail >= rq->ring->size);
> +	assert_ring_tail_valid(rq->ring, rq->tail);
>  	reg_state[CTX_RING_TAIL+1] = rq->tail;
>  
>  	/* True 32b PPGTT with dynamic page allocation: update PDP
> @@ -1282,8 +1281,7 @@ static void reset_common_ring(struct intel_engine_cs *engine,
>  	request->tail =
>  		intel_ring_wrap(request->ring,
>  				request->wa_tail - WA_TAIL_DWORDS*sizeof(u32));
> -	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
> -	GEM_BUG_ON(request->tail >= request->ring->size);
> +	assert_ring_tail_valid(request->ring, request->tail);
>  }
>  
>  static int intel_logical_ring_emit_pdps(struct drm_i915_gem_request *req)
> @@ -1494,8 +1492,7 @@ static void gen8_emit_breadcrumb(struct drm_i915_gem_request *request, u32 *cs)
>  	*cs++ = MI_USER_INTERRUPT;
>  	*cs++ = MI_NOOP;
>  	request->tail = intel_ring_offset(request, cs);
> -	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
> -	GEM_BUG_ON(request->tail >= request->ring->size);
> +	assert_ring_tail_valid(request->ring, request->tail);
>  
>  	gen8_emit_wa_tail(request, cs);
>  }
> @@ -1523,8 +1520,7 @@ static void gen8_emit_breadcrumb_render(struct drm_i915_gem_request *request,
>  	*cs++ = MI_USER_INTERRUPT;
>  	*cs++ = MI_NOOP;
>  	request->tail = intel_ring_offset(request, cs);
> -	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
> -	GEM_BUG_ON(request->tail >= request->ring->size);
> +	assert_ring_tail_valid(request->ring, request->tail);
>  
>  	gen8_emit_wa_tail(request, cs);
>  }
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 47921dcbedb3..66a2b8b83972 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -774,8 +774,7 @@ static void i9xx_submit_request(struct drm_i915_gem_request *request)
>  
>  	i915_gem_request_submit(request);
>  
> -	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
> -	GEM_BUG_ON(request->tail >= request->ring->size);
> +	assert_ring_tail_valid(request->ring, request->tail);
>  	I915_WRITE_TAIL(request->engine, request->tail);
>  }
>  
> @@ -787,8 +786,7 @@ static void i9xx_emit_breadcrumb(struct drm_i915_gem_request *req, u32 *cs)
>  	*cs++ = MI_USER_INTERRUPT;
>  
>  	req->tail = intel_ring_offset(req, cs);
> -	GEM_BUG_ON(!IS_ALIGNED(req->tail, 8));
> -	GEM_BUG_ON(req->tail >= req->ring->size);
> +	assert_ring_tail_valid(req->ring, req->tail);
>  }
>  
>  static const int i9xx_emit_breadcrumb_sz = 4;
> @@ -827,8 +825,7 @@ static void gen8_render_emit_breadcrumb(struct drm_i915_gem_request *req,
>  	*cs++ = MI_NOOP;
>  
>  	req->tail = intel_ring_offset(req, cs);
> -	GEM_BUG_ON(!IS_ALIGNED(req->tail, 8));
> -	GEM_BUG_ON(req->tail >= req->ring->size);
> +	assert_ring_tail_valid(req->ring, req->tail);
>  }
>  
>  static const int gen8_render_emit_breadcrumb_sz = 8;
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 17ac44980d84..a82a0807f64d 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -529,6 +529,17 @@ intel_ring_offset(const struct drm_i915_gem_request *req, void *addr)
>  	return intel_ring_wrap(req->ring, offset);
>  }
>  
> +static inline void
> +assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail)
> +{
> +	/* We could combine these into a single tail operation, but keeping
> +	 * them as seperate tests will help identify the cause should one
> +	 * ever fire.
> +	 */
> +	GEM_BUG_ON(!IS_ALIGNED(tail, 8));
> +	GEM_BUG_ON(tail >= ring->size);
> +}
> +
>  void intel_ring_update_space(struct intel_ring *ring);
>  
>  void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno);
> -- 
> 2.11.0
>
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