[PATCH v2 1/2] drm/i915: Add perf property support for context HW id

[Lionel Landwerlin]

Just a small nit down there.

On 19/07/17 06:39, Zhenyu Wang wrote:
> In order to support profiling for special context e.g vGPU context,
> we can expose vGPU context hw id and enable i915 perf property to
> get target context for profiling. This adds new perf property to
> assign target context with hw id.
>
> Jiao Pengyuan has helped to fix context reference bug in original code.
>
> v2:
> - new function for context lookup with hw id
> - always require priviledged op
> - fix error return value
>
> Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jiao Pengyuan <pengyuan.jiao at intel.com>
> Cc: Niu Bing <bing.niu at intel.com>
> Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_perf.c | 83 ++++++++++++++++++++++++++++++++--------
>   include/uapi/drm/i915_drm.h      |  5 +++
>   2 files changed, 72 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 96682fd86f82..a80a3959bc3b 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -334,7 +334,9 @@ static struct i915_oa_format gen8_plus_oa_formats[I915_OA_FORMAT_MAX] = {
>    * struct perf_open_properties - for validated properties given to open a stream
>    * @sample_flags: `DRM_I915_PERF_PROP_SAMPLE_*` properties are tracked as flags
>    * @single_context: Whether a single or all gpu contexts should be monitored
> + * @single_context_hw: Set for special context with hw id e.g vGPU
>    * @ctx_handle: A gem ctx handle for use with @single_context
> + * @ctx_hw_id: A ctx hw id for use with @single_context_hw
>    * @metrics_set: An ID for an OA unit metric set advertised via sysfs
>    * @oa_format: An OA unit HW report format
>    * @oa_periodic: Whether to enable periodic OA unit sampling
> @@ -348,7 +350,9 @@ struct perf_open_properties {
>   	u32 sample_flags;
>   
>   	u64 single_context:1;
> +	u64 single_context_hw:1;
>   	u64 ctx_handle;
> +	u64 ctx_hw_id;
>   
>   	/* OA sampling state */
>   	int metrics_set;
> @@ -2482,6 +2486,29 @@ static const struct file_operations fops = {
>   	.unlocked_ioctl	= i915_perf_ioctl,
>   };
>   
> +static struct i915_gem_context *
> +lookup_context_hw_id(struct drm_i915_private *dev_priv, unsigned int hw_id)
> +{
> +	struct i915_gem_context *ctx;
> +	int ret;
> +
> +	ret = i915_mutex_lock_interruptible(&dev_priv->drm);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	list_for_each_entry(ctx, &dev_priv->contexts.list, link) {
> +		if (!i915_gem_context_is_default(ctx))
> +			continue;
> +
> +		if (ctx->hw_id == hw_id) {
> +			ret = 1;
> +			i915_gem_context_get(ctx);
> +			break;
> +		}
> +	}
> +	mutex_unlock(&dev_priv->drm.struct_mutex);
> +	return ret ? ctx : NULL;

I think you should replace NULL by ERR_PTR(-ENOENT) here, that would 
simplify the call to lookup_context_hw_id().

> +}
>   
>   /**
>    * i915_perf_open_ioctl_locked - DRM ioctl() for userspace to open a stream FD
> @@ -2531,24 +2558,35 @@ i915_perf_open_ioctl_locked(struct drm_i915_private *dev_priv,
>   			ret = -ENOENT;
>   			goto err;
>   		}
> +
> +		/*
> +		 * On Haswell the OA unit supports clock gating off for a specific
> +		 * context and in this mode there's no visibility of metrics for the
> +		 * rest of the system, which we consider acceptable for a
> +		 * non-privileged client.
> +		 *
> +		 * For Gen8+ the OA unit no longer supports clock gating off for a
> +		 * specific context and the kernel can't securely stop the counters
> +		 * from updating as system-wide / global values. Even though we can
> +		 * filter reports based on the included context ID we can't block
> +		 * clients from seeing the raw / global counter values via
> +		 * MI_REPORT_PERF_COUNT commands and so consider it a privileged op to
> +		 * enable the OA unit by default.
> +		 */
> +		if (IS_HASWELL(dev_priv) && specific_ctx)
> +			privileged_op = false;
>   	}
>   
> -	/*
> -	 * On Haswell the OA unit supports clock gating off for a specific
> -	 * context and in this mode there's no visibility of metrics for the
> -	 * rest of the system, which we consider acceptable for a
> -	 * non-privileged client.
> -	 *
> -	 * For Gen8+ the OA unit no longer supports clock gating off for a
> -	 * specific context and the kernel can't securely stop the counters
> -	 * from updating as system-wide / global values. Even though we can
> -	 * filter reports based on the included context ID we can't block
> -	 * clients from seeing the raw / global counter values via
> -	 * MI_REPORT_PERF_COUNT commands and so consider it a privileged op to
> -	 * enable the OA unit by default.
> -	 */
> -	if (IS_HASWELL(dev_priv) && specific_ctx)
> -		privileged_op = false;
> +	if (props->single_context_hw) {
> +		unsigned int hw_id = props->ctx_hw_id;
> +
> +		specific_ctx = lookup_context_hw_id(dev_priv, hw_id);
> +		if (IS_ERR_OR_NULL(specific_ctx)) {
> +			DRM_DEBUG("Failed to look up HW context id.\n");
> +			ret = -ENOENT;
> +			goto err;
> +		}

If you change lookup_context_hw_id() as indicated above, this can be 
turned into :

if (IS_ERR(specific_ctx)) {
    DRM_DEBUG(...);
    ret = PTR_ERR(specific_ctx);
    goto err;
}

> +	}
>   
>   	/* Similar to perf's kernel.perf_paranoid_cpu sysctl option
>   	 * we check a dev.i915.perf_stream_paranoid sysctl option
> @@ -2686,6 +2724,14 @@ static int read_properties_unlocked(struct drm_i915_private *dev_priv,
>   			props->single_context = 1;
>   			props->ctx_handle = value;
>   			break;
> +		case DRM_I915_PERF_PROP_CTX_HW_ID:
> +			if (value >= MAX_CONTEXT_HW_ID) {
> +				DRM_DEBUG("Invalid OA HW context ID\n");
> +				return -EINVAL;
> +			}
> +			props->single_context_hw = 1;
> +			props->ctx_hw_id = value;
> +			break;
>   		case DRM_I915_PERF_PROP_SAMPLE_OA:
>   			props->sample_flags |= SAMPLE_OA_REPORT;
>   			break;
> @@ -2757,6 +2803,11 @@ static int read_properties_unlocked(struct drm_i915_private *dev_priv,
>   		uprop += 2;
>   	}
>   
> +	if (props->single_context && props->single_context_hw) {
> +		DRM_DEBUG("Assign context handler and HW id simultaneously\n");
> +		return -EINVAL;
> +	}
> +
>   	return 0;
>   }
>   
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 7ccbd6a2bbe0..ddafa556e290 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1381,6 +1381,11 @@ enum drm_i915_perf_property_id {
>   	 */
>   	DRM_I915_PERF_PROP_OA_EXPONENT,
>   
> +	/**
> +	 * The value specifies ctx with hw_id
> +	 */
> +	DRM_I915_PERF_PROP_CTX_HW_ID,
> +
>   	DRM_I915_PERF_PROP_MAX /* non-ABI */
>   };
>