Re: [PATCH 18/27] drm/i915/gem: Optionally set SSEU in intel_context_set_gem

Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> · Wed, 5 May 2021 10:52:56 +0100

On 05/05/2021 10:47, Daniel Vetter wrote:
On Wed, May 05, 2021 at 10:28:59AM +0100, Tvrtko Ursulin wrote:

On 04/05/2021 20:00, Daniel Vetter wrote:
On Mon, May 03, 2021 at 10:57:39AM -0500, Jason Ekstrand wrote:
For now this is a no-op because everyone passes in a null SSEU but it
lets us get some of the error handling and selftest refactoring plumbed
through.

Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>

it is a bit icky that intel_context_set_gem also sets the sseu, feels a
bit like a layering violation, but welp I couldn't come up with a better
idea either.

Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

It is actually quite horrible. As you say it breaks separation of duties and
open codes stuff all over the place without transferring over the commentary
about why.

I didn't really see lost commentary anywhere? Can you pls point out what
got lost?

I glanced over two new places which check for RENDER_CLASS without any 
commentary while the existing code helpfully says:

	/* Only render engine supports RPCS configuration. */
	if (ce->engine->class != RENDER_CLASS) {
		ret = -ENODEV;
		goto out_ce;
	}

But really that is really just a symptom how mixed up the flows end up 
with this patch. In other words I am not suggesting those two new sites 
should have the same comment, just highlighting that the design is not good.

Regards,

Tvrtko

 -Daniel


Regards,

Tvrtko

---
   drivers/gpu/drm/i915/gem/i915_gem_context.c   | 41 +++++++++++++++----
   .../gpu/drm/i915/gem/selftests/mock_context.c |  6 ++-
   2 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index ce729e640bbf7..6dd50d669c5b9 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -320,9 +320,12 @@ context_get_vm_rcu(struct i915_gem_context *ctx)
   	} while (1);
   }
-static void intel_context_set_gem(struct intel_context *ce,
-				  struct i915_gem_context *ctx)
+static int intel_context_set_gem(struct intel_context *ce,
+				 struct i915_gem_context *ctx,
+				 struct intel_sseu sseu)
   {
+	int ret = 0;
+
   	GEM_BUG_ON(rcu_access_pointer(ce->gem_context));
   	RCU_INIT_POINTER(ce->gem_context, ctx);
@@ -349,6 +352,12 @@ static void intel_context_set_gem(struct intel_context *ce,
   		intel_context_set_watchdog_us(ce, (u64)timeout_ms * 1000);
   	}
+
+	/* A valid SSEU has no zero fields */
+	if (sseu.slice_mask && !WARN_ON(ce->engine->class != RENDER_CLASS))
+		ret = intel_context_reconfigure_sseu(ce, sseu);
+
+	return ret;
   }
   static void __free_engines(struct i915_gem_engines *e, unsigned int count)
@@ -416,7 +425,8 @@ static struct i915_gem_engines *alloc_engines(unsigned int count)
   	return e;
   }
-static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
+static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx,
+						struct intel_sseu rcs_sseu)
   {
   	const struct intel_gt *gt = &ctx->i915->gt;
   	struct intel_engine_cs *engine;
@@ -429,6 +439,8 @@ static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
   	for_each_engine(engine, gt, id) {
   		struct intel_context *ce;
+		struct intel_sseu sseu = {};
+		int ret;
   		if (engine->legacy_idx == INVALID_ENGINE)
   			continue;
@@ -442,10 +454,18 @@ static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
   			goto free_engines;
   		}
-		intel_context_set_gem(ce, ctx);
-
   		e->engines[engine->legacy_idx] = ce;
   		e->num_engines = max(e->num_engines, engine->legacy_idx + 1);
+
+		if (engine->class == RENDER_CLASS)
+			sseu = rcs_sseu;
+
+		ret = intel_context_set_gem(ce, ctx, sseu);
+		if (ret) {
+			err = ERR_PTR(ret);
+			goto free_engines;
+		}
+
   	}
   	return e;
@@ -759,6 +779,7 @@ __create_context(struct drm_i915_private *i915,
   {
   	struct i915_gem_context *ctx;
   	struct i915_gem_engines *e;
+	struct intel_sseu null_sseu = {};
   	int err;
   	int i;
@@ -776,7 +797,7 @@ __create_context(struct drm_i915_private *i915,
   	INIT_LIST_HEAD(&ctx->stale.engines);
   	mutex_init(&ctx->engines_mutex);
-	e = default_engines(ctx);
+	e = default_engines(ctx, null_sseu);
   	if (IS_ERR(e)) {
   		err = PTR_ERR(e);
   		goto err_free;
@@ -1544,6 +1565,7 @@ set_engines__load_balance(struct i915_user_extension __user *base, void *data)
   	struct intel_engine_cs *stack[16];
   	struct intel_engine_cs **siblings;
   	struct intel_context *ce;
+	struct intel_sseu null_sseu = {};
   	u16 num_siblings, idx;
   	unsigned int n;
   	int err;
@@ -1616,7 +1638,7 @@ set_engines__load_balance(struct i915_user_extension __user *base, void *data)
   		goto out_siblings;
   	}
-	intel_context_set_gem(ce, set->ctx);
+	intel_context_set_gem(ce, set->ctx, null_sseu);
   	if (cmpxchg(&set->engines->engines[idx], NULL, ce)) {
   		intel_context_put(ce);
@@ -1724,6 +1746,7 @@ set_engines(struct i915_gem_context *ctx,
   	struct drm_i915_private *i915 = ctx->i915;
   	struct i915_context_param_engines __user *user =
   		u64_to_user_ptr(args->value);
+	struct intel_sseu null_sseu = {};
   	struct set_engines set = { .ctx = ctx };
   	unsigned int num_engines, n;
   	u64 extensions;
@@ -1733,7 +1756,7 @@ set_engines(struct i915_gem_context *ctx,
   		if (!i915_gem_context_user_engines(ctx))
   			return 0;
-		set.engines = default_engines(ctx);
+		set.engines = default_engines(ctx, null_sseu);
   		if (IS_ERR(set.engines))
   			return PTR_ERR(set.engines);
@@ -1790,7 +1813,7 @@ set_engines(struct i915_gem_context *ctx,
   			return PTR_ERR(ce);
   		}
-		intel_context_set_gem(ce, ctx);
+		intel_context_set_gem(ce, ctx, null_sseu);
   		set.engines->engines[n] = ce;
   	}
diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_context.c b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
index e0f512ef7f3c6..cbeefd060e97b 100644
--- a/drivers/gpu/drm/i915/gem/selftests/mock_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
@@ -14,6 +14,7 @@ mock_context(struct drm_i915_private *i915,
   {
   	struct i915_gem_context *ctx;
   	struct i915_gem_engines *e;
+	struct intel_sseu null_sseu = {};
   	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
   	if (!ctx)
@@ -31,7 +32,7 @@ mock_context(struct drm_i915_private *i915,
   	i915_gem_context_set_persistence(ctx);
   	mutex_init(&ctx->engines_mutex);
-	e = default_engines(ctx);
+	e = default_engines(ctx, null_sseu);
   	if (IS_ERR(e))
   		goto err_free;
   	RCU_INIT_POINTER(ctx->engines, e);
@@ -112,6 +113,7 @@ live_context_for_engine(struct intel_engine_cs *engine, struct file *file)
   {
   	struct i915_gem_engines *engines;
   	struct i915_gem_context *ctx;
+	struct intel_sseu null_sseu = {};
   	struct intel_context *ce;
   	engines = alloc_engines(1);
@@ -130,7 +132,7 @@ live_context_for_engine(struct intel_engine_cs *engine, struct file *file)
   		return ERR_CAST(ce);
   	}
-	intel_context_set_gem(ce, ctx);
+	intel_context_set_gem(ce, ctx, null_sseu);
   	engines->engines[0] = ce;
   	engines->num_engines = 1;
--
2.31.1

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