[Intel-gfx] [PATCH] drm/i915: fix crash in error state readout on non-execlist platforms

[Yu Dai]

Jesse,

Will the patch here fix the issue? It should help other cases where 
LRC_PPHWSP_PN is referenced on non-execlist / guc platforms.

diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 4cc54b3..233a930 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -71,7 +71,7 @@ static inline void intel_logical_ring_emit(struct intel_ringbuffer *ringbuf,

  /* One extra page is added before LRC for GuC as shared data */
  #define LRC_GUCSHR_PN  (0)
-#define LRC_PPHWSP_PN  (LRC_GUCSHR_PN + 1)
+#define LRC_PPHWSP_PN  (LRC_GUCSHR_PN + i915.enable_guc_submission ? 1 : 0)
  #define LRC_STATE_PN   (LRC_PPHWSP_PN + 1)

  void intel_lr_context_free(struct intel_context *ctx);

Thanks,
Alex

On 09/10/2015 02:40 PM, Jesse Barnes wrote:
> Looks like this was introduced in:
> commit d1675198ed1f21aec6e036336e4340c40b726497
> Author: Alex Dai <yu.dai at intel.com>
> Date:   Wed Aug 12 15:43:43 2015 +0100
>
>      drm/i915: Integrate GuC-based command submission
>
> This patch assumed LRC contexts and HWS layout, which is incorrect on
> platforms without execlists.  This can lead to a crash in GPU error
> state readout on those platforms.
>
> I don't see a bug filed for this, but there may be one that I haven't
> found.
>
> Cc: Alex Dai <yu.dai at intel.com>
> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> ---
>   drivers/gpu/drm/i915/i915_gpu_error.c | 19 +++++++++++++------
>   1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index 3379f9c..d0822f8 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -457,17 +457,24 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
>   		}
>   
>   		if ((obj = error->ring[i].hws_page)) {
> +			u64 hws_offset = lower_32_bits(obj->gtt_offset);
> +			u32 *hws_page = &obj->pages[0][0];
> +
> +			if (i915.enable_execlists) {
> +				hws_offset = obj->gtt_offset + LRC_PPHWSP_PN *
> +					PAGE_SIZE;
> +				hws_page = &obj->pages[LRC_PPHWSP_PN][0];
> +			}
>   			err_printf(m, "%s --- HW Status = 0x%08llx\n",
> -				dev_priv->ring[i].name,
> -				obj->gtt_offset + LRC_PPHWSP_PN * PAGE_SIZE);
> +				   dev_priv->ring[i].name, hws_offset);
>   			offset = 0;
>   			for (elt = 0; elt < PAGE_SIZE/16; elt += 4) {
>   				err_printf(m, "[%04x] %08x %08x %08x %08x\n",
>   					   offset,
> -					   obj->pages[LRC_PPHWSP_PN][elt],
> -					   obj->pages[LRC_PPHWSP_PN][elt+1],
> -					   obj->pages[LRC_PPHWSP_PN][elt+2],
> -					   obj->pages[LRC_PPHWSP_PN][elt+3]);
> +					   hws_page[elt],
> +					   hws_page[elt+1],
> +					   hws_page[elt+2],
> +					   hws_page[elt+3]);
>   					offset += 16;
>   			}
>   		}