Re: [PATCH v2 2/3] drm/i915: Assert that the request->tail fits within the ring

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

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

> In addition to being qword-aligned, the RING_TAIL offset must be within
> the ring!
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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

> ---
>  drivers/gpu/drm/i915/intel_lrc.c        | 4 ++++
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
>  2 files changed, 7 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 32fb8ad3fd36..39cb84a5d4e4 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -327,6 +327,7 @@ static u64 execlists_update_context(struct drm_i915_gem_request *rq)
>  	u32 *reg_state = ce->lrc_reg_state;
>  
>  	GEM_BUG_ON(!IS_ALIGNED(rq->tail, 8));
> +	GEM_BUG_ON(rq->tail >= rq->ring->size);
>  	reg_state[CTX_RING_TAIL+1] = rq->tail;
>  
>  	/* True 32b PPGTT with dynamic page allocation: update PDP
> @@ -1282,6 +1283,7 @@ static void reset_common_ring(struct intel_engine_cs *engine,
>  		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);
>  }
>  
>  static int intel_logical_ring_emit_pdps(struct drm_i915_gem_request *req)
> @@ -1493,6 +1495,7 @@ static void gen8_emit_breadcrumb(struct drm_i915_gem_request *request, u32 *cs)
>  	*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);
>  
>  	gen8_emit_wa_tail(request, cs);
>  }
> @@ -1521,6 +1524,7 @@ static void gen8_emit_breadcrumb_render(struct drm_i915_gem_request *request,
>  	*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);
>  
>  	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 4729ac7ac122..47921dcbedb3 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -775,6 +775,7 @@ 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);
>  	I915_WRITE_TAIL(request->engine, request->tail);
>  }
>  
> @@ -787,6 +788,7 @@ static void i9xx_emit_breadcrumb(struct drm_i915_gem_request *req, u32 *cs)
>  
>  	req->tail = intel_ring_offset(req, cs);
>  	GEM_BUG_ON(!IS_ALIGNED(req->tail, 8));
> +	GEM_BUG_ON(req->tail >= req->ring->size);
>  }
>  
>  static const int i9xx_emit_breadcrumb_sz = 4;
> @@ -826,6 +828,7 @@ static void gen8_render_emit_breadcrumb(struct drm_i915_gem_request *req,
>  
>  	req->tail = intel_ring_offset(req, cs);
>  	GEM_BUG_ON(!IS_ALIGNED(req->tail, 8));
> +	GEM_BUG_ON(req->tail >= req->ring->size);
>  }
>  
>  static const int gen8_render_emit_breadcrumb_sz = 8;
> -- 
> 2.11.0
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