drm/i915: Shadow default engine context image in the context

To enable adding override of the default engine context image let us start
shadowing the per engine state in the context.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Carlos Santa <carlos.santa@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Tvrtko Ursulin <tursulin@igalia.com>
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20240514145939.87427-1-tursulin@igalia.com

drivers/gpu/drm/i915/gt/intel_context_types.h

@@ -99,6 +99,8 @@ struct intel_context {
 	struct i915_address_space *vm;
 	struct i915_gem_context __rcu *gem_context;
 
+	struct file *default_state;
+
 	/*
 	 * @signal_lock protects the list of requests that need signaling,
 	 * @signals. While there are any requests that need signaling,

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -1017,9 +1017,8 @@ void lrc_init_state(struct intel_context *ce,
 
 	set_redzone(state, engine);
 
-	if (engine->default_state) {
-		shmem_read(engine->default_state, 0,
-			   state, engine->context_size);
+	if (ce->default_state) {
+		shmem_read(ce->default_state, 0, state, engine->context_size);
 		__set_bit(CONTEXT_VALID_BIT, &ce->flags);
 		inhibit = false;
 	}
@@ -1131,6 +1130,8 @@ int lrc_alloc(struct intel_context *ce, struct intel_engine_cs *engine)
 
 	GEM_BUG_ON(ce->state);
 
+	ce->default_state = engine->default_state;
+
 	vma = __lrc_alloc_state(ce, engine);
 	if (IS_ERR(vma))
 		return PTR_ERR(vma);

drivers/gpu/drm/i915/gt/intel_ring_submission.c

@@ -474,8 +474,7 @@ static int ring_context_init_default_state(struct intel_context *ce,
 	if (IS_ERR(vaddr))
 		return PTR_ERR(vaddr);
 
-	shmem_read(ce->engine->default_state, 0,
-		   vaddr, ce->engine->context_size);
+	shmem_read(ce->default_state, 0, vaddr, ce->engine->context_size);
 
 	i915_gem_object_flush_map(obj);
 	__i915_gem_object_release_map(obj);
@@ -491,7 +490,7 @@ static int ring_context_pre_pin(struct intel_context *ce,
 	struct i915_address_space *vm;
 	int err = 0;
 
-	if (ce->engine->default_state &&
+	if (ce->default_state &&
 	    !test_bit(CONTEXT_VALID_BIT, &ce->flags)) {
 		err = ring_context_init_default_state(ce, ww);
 		if (err)
@@ -570,6 +569,8 @@ static int ring_context_alloc(struct intel_context *ce)
 {
 	struct intel_engine_cs *engine = ce->engine;
 
+	ce->default_state = engine->default_state;
+
 	/* One ringbuffer to rule them all */
 	GEM_BUG_ON(!engine->legacy.ring);
 	ce->ring = engine->legacy.ring;