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

[Zhenyu Wang]

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;
+}
 
 /**
  * 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;
+		}
+	}
 
 	/* 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 */
 };
 
-- 
2.13.2