drm/i915: Extend I915_CONTEXT_PARAM_SSEU to support local ctx->engine[]

Allow the user to specify a local engine index (as opposed to
class:index) that they can use to refer to a preset engine inside the
ctx->engine[] array defined by an earlier I915_CONTEXT_PARAM_ENGINES.
This will be useful for setting SSEU parameters on virtual engines that
are local to the context and do not have a valid global class:instance
lookup.

Note that due to the ambiguity in using class:instance with
ctx->engines[], if a user supplied engine map is active the user must
specify the engine to alter by its index into the ctx->engines[].

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190521211134.16117-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_context.c

@@ -1363,6 +1363,7 @@ static int set_sseu(struct i915_gem_context *ctx,
 	struct drm_i915_gem_context_param_sseu user_sseu;
 	struct intel_context *ce;
 	struct intel_sseu sseu;
+	unsigned long lookup;
 	int ret;
 
 	if (args->size < sizeof(user_sseu))
@@ -1375,10 +1376,17 @@ static int set_sseu(struct i915_gem_context *ctx,
 			   sizeof(user_sseu)))
 		return -EFAULT;
 
-	if (user_sseu.flags || user_sseu.rsvd)
+	if (user_sseu.rsvd)
 		return -EINVAL;
 
-	ce = lookup_user_engine(ctx, 0, &user_sseu.engine);
+	if (user_sseu.flags & ~(I915_CONTEXT_SSEU_FLAG_ENGINE_INDEX))
+		return -EINVAL;
+
+	lookup = 0;
+	if (user_sseu.flags & I915_CONTEXT_SSEU_FLAG_ENGINE_INDEX)
+		lookup |= LOOKUP_USER_INDEX;
+
+	ce = lookup_user_engine(ctx, lookup, &user_sseu.engine);
 	if (IS_ERR(ce))
 		return PTR_ERR(ce);
 
@@ -1821,6 +1829,7 @@ static int get_sseu(struct i915_gem_context *ctx,
 {
 	struct drm_i915_gem_context_param_sseu user_sseu;
 	struct intel_context *ce;
+	unsigned long lookup;
 	int err;
 
 	if (args->size == 0)
@@ -1832,10 +1841,17 @@ static int get_sseu(struct i915_gem_context *ctx,
 			   sizeof(user_sseu)))
 		return -EFAULT;
 
-	if (user_sseu.flags || user_sseu.rsvd)
+	if (user_sseu.rsvd)
 		return -EINVAL;
 
-	ce = lookup_user_engine(ctx, 0, &user_sseu.engine);
+	if (user_sseu.flags & ~(I915_CONTEXT_SSEU_FLAG_ENGINE_INDEX))
+		return -EINVAL;
+
+	lookup = 0;
+	if (user_sseu.flags & I915_CONTEXT_SSEU_FLAG_ENGINE_INDEX)
+		lookup |= LOOKUP_USER_INDEX;
+
+	ce = lookup_user_engine(ctx, lookup, &user_sseu.engine);
 	if (IS_ERR(ce))
 		return PTR_ERR(ce);
 

include/uapi/drm/i915_drm.h

@@ -1576,9 +1576,10 @@ struct drm_i915_gem_context_param_sseu {
 	struct i915_engine_class_instance engine;
 
 	/*
-	 * Unused for now. Must be cleared to zero.
+	 * Unknown flags must be cleared to zero.
 	 */
 	__u32 flags;
+#define I915_CONTEXT_SSEU_FLAG_ENGINE_INDEX (1u << 0)
 
 	/*
 	 * Mask of slices to enable for the context. Valid values are a subset