Re: [Intel-gfx] [RFC PATCH 07/11] drm/i915: Expose PMU for Observation Architecture

On 7 May 2015 15:37, "Chris Wilson" chris@chris-wilson.co.uk wrote:

On Thu, May 07, 2015 at 03:15:50PM +0100, Robert Bragg wrote:

...

+static int init_oa_buffer(struct perf_event *event) +{

• struct drm_i915_private *dev_priv =
  

•         container_of(event->pmu, typeof(*dev_priv), oa_pmu.pmu);
  

• struct drm_i915_gem_object *bo;
  

• int ret;
  

• BUG_ON(!IS_HASWELL(dev_priv->dev));
  

• BUG_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
  

• BUG_ON(dev_priv->oa_pmu.oa_buffer.obj);
  

• spin_lock_init(&dev_priv->oa_pmu.oa_buffer.flush_lock);
  

• /* NB: We over allocate the OA buffer due to the way raw sample
  

data

...

•  * gets copied from the gpu mapped circular buffer into the perf
  

•  * circular buffer so that only one copy is required.
  

•  *
  

•  * For each perf sample (raw->size + 4) needs to be 8 byte
  

aligned,

...

•  * where the 4 corresponds to the 32bit raw->size member that's
  

•  * added to the sample header that userspace sees.
  

•  *
  

•  * Due to the + 4 for the size member: when we copy a report to
  

the

...

•  * userspace facing perf buffer we always copy an additional 4
  

bytes

...

•  * from the subsequent report to make up for the miss alignment,
  

but

...

•  * when a report is at the end of the gpu mapped buffer we need to
  

•  * read 4 bytes past the end of the buffer.
  

•  */
  

• bo = i915_gem_alloc_object(dev_priv->dev, OA_BUFFER_SIZE +
  

PAGE_SIZE);

...

• if (bo == NULL) {
  

•         DRM_ERROR("Failed to allocate OA buffer\n");
  

•         ret = -ENOMEM;
  

•         goto err;
  

• }
  

• dev_priv->oa_pmu.oa_buffer.obj = bo;
  

• ret = i915_gem_object_set_cache_level(bo, I915_CACHE_LLC);
  

• if (ret)
  

•         goto err_unref;
  

• /* PreHSW required 512K alignment, HSW requires 16M */
  

• ret = i915_gem_obj_ggtt_pin(bo, SZ_16M, 0);
  

• if (ret)
  

•         goto err_unref;
  

• dev_priv->oa_pmu.oa_buffer.gtt_offset =
  

i915_gem_obj_ggtt_offset(bo);

...

• dev_priv->oa_pmu.oa_buffer.addr = vmap_oa_buffer(bo);
  

You can look forward to both i915_gem_object_create_internal() and i915_gem_object_pin_vmap()

Okey, will do, thanks.

...

• /* Pre-DevBDW: OABUFFER must be set with counters off,
  

•  * before OASTATUS1, but after OASTATUS2 */
  

• I915_WRITE(GEN7_OASTATUS2, dev_priv->oa_pmu.oa_buffer.gtt_offset |
  

•            GEN7_OASTATUS2_GGTT); /* head */
  

• I915_WRITE(GEN7_OABUFFER, dev_priv->oa_pmu.oa_buffer.gtt_offset);
  

• I915_WRITE(GEN7_OASTATUS1, dev_priv->oa_pmu.oa_buffer.gtt_offset |
  

•            GEN7_OASTATUS1_OABUFFER_SIZE_16M); /* tail */
  

• DRM_DEBUG_DRIVER("OA Buffer initialized, gtt offset = 0x%x, vaddr
  

= %p",

...

•                  dev_priv->oa_pmu.oa_buffer.gtt_offset,
  

•                  dev_priv->oa_pmu.oa_buffer.addr);
  

• return 0;
  

+err_unref:

• drm_gem_object_unreference_unlocked(&bo->base);
  

But what I really what to say was: mutex deadlock^^^

Yikes, I've pushed an updated patch addressing this and can reply with a new patch here in a bit.

Thanks, - Robert

-Chris

-- Chris Wilson, Intel Open Source Technology Centre