[Intel-gfx] [PATCH v5 18/18] drm/i915: Watchdog timeout: Export media reset count from GuC to debugfs

[Chris Wilson]

On Fri, Mar 24, 2017 at 06:30:10PM -0700, Michel Thierry wrote:
> From firmware v8.8, GuC provides the count of media engine resets
> (watchdog timeout). This information is available in the GuC shared
> context data struct, which resides in the first page of the default
> (kernel) lrc context.
> 
> Since GuC handled engine resets are transparent for kernel and user,
> provide a simple debugfs entry to see the number of times media reset
> has happened.
> 
> Signed-off-by: Michel Thierry <michel.thierry at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c   | 28 ++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_guc_fwif.h | 18 ++++++++++++++++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 8db850541e03..f40a2c84b423 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -1400,6 +1400,32 @@ static int i915_hangcheck_info(struct seq_file *m, void *unused)
>  	return 0;
>  }
>  
> +static u32 i915_watchdog_reset_count(struct drm_i915_private *dev_priv)
> +{
> +	struct drm_device *dev = &dev_priv->drm;
> +	struct i915_gem_context *ctx;
> +	struct page *page;
> +	struct guc_shared_ctx_data *guc_shared_data;
> +	u32 guc_media_reset_count;
> +
> +	if (!i915.enable_guc_submission)
> +		return 0;
> +
> +	if (mutex_lock_interruptible(&dev->struct_mutex))
> +		return 0;

Do you need the mutex?

> +	ctx = dev_priv->kernel_context;
> +	page = i915_gem_object_get_dirty_page(ctx->engine[RCS].state->obj,
> +					      LRC_GUCSHR_PN);

Are you writing?

> +	guc_shared_data = kmap_atomic(page);

Atomic?

> +	guc_media_reset_count = guc_shared_data->media_reset_count;

This is an unserialised access, mark it so (READ_ONCE).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre