[Intel-gfx] [PATCH 07/26] drm/i915/guc: Introduce context parent-child relationship

Matthew Brost
2021-10-04T22:11:52Z

Introduce context parent-child relationship. Once this relationship is
created all pinning / unpinning operations are directed to the parent
context. The parent context is responsible for pinning all of its'
children and itself.

This is a precursor to the full GuC multi-lrc implementation but aligns
to how GuC mutli-lrc interface is defined - a single H2G is used
register / deregister all of the contexts simultaneously.

Subsequent patches in the series will implement the pinning / unpinning
operations for parent / child contexts.

v2:
(Daniel Vetter)
- Add kernel doc, add wrapper to access parent to ensure safety
v3:
(John Harrison)
- Fix comment explaing GEM_BUG_ON in to_parent()
- Make variable names generic (non-GuC specific)

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
drivers/gpu/drm/i915/gt/intel_context.c | 29 +++++++++++++
drivers/gpu/drm/i915/gt/intel_context.h | 41 +++++++++++++++++++
drivers/gpu/drm/i915/gt/intel_context_types.h | 21 ++++++++++
3 files changed, 91 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index f601323b939f..c5bb7ccfb3f8 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -403,6 +403,8 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)

INIT_LIST_HEAD(&ce->destroyed_link);

+ INIT_LIST_HEAD(&ce->parallel.child_list);
+
/*
* Initialize fence to be complete as this is expected to be complete
* unless there is a pending schedule disable outstanding.
@@ -417,10 +419,17 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)

void intel_context_fini(struct intel_context *ce)
{
+ struct intel_context *child, *next;
+
if (ce->timeline)
intel_timeline_put(ce->timeline);
i915_vm_put(ce->vm);

+ /* Need to put the creation ref for the children */
+ if (intel_context_is_parent(ce))
+ for_each_child_safe(ce, child, next)
+ intel_context_put(child);
+
mutex_destroy(&ce->pin_mutex);
i915_active_fini(&ce->active);
i915_sw_fence_fini(&ce->guc_state.blocked);
@@ -537,6 +546,26 @@ struct i915_request *intel_context_find_active_request(struct intel_context *ce)
return active;
}

+void intel_context_bind_parent_child(struct intel_context *parent,
+ struct intel_context *child)
+{
+ /*
+ * Callers responsibility to validate that this function is used
+ * correctly but we use GEM_BUG_ON here ensure that they do.
+ */
+ GEM_BUG_ON(!intel_engine_uses_guc(parent->engine));
+ GEM_BUG_ON(intel_context_is_pinned(parent));
+ GEM_BUG_ON(intel_context_is_child(parent));
+ GEM_BUG_ON(intel_context_is_pinned(child));
+ GEM_BUG_ON(intel_context_is_child(child));
+ GEM_BUG_ON(intel_context_is_parent(child));
+
+ parent->parallel.number_children++;
+ list_add_tail(&child->parallel.child_link,
+ &parent->parallel.child_list);
+ child->parallel.parent = parent;
+}
+
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_context.c"
#endif
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index c41098950746..b63c10a144af 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -44,6 +44,47 @@ void intel_context_free(struct intel_context *ce);
int intel_context_reconfigure_sseu(struct intel_context *ce,
const struct intel_sseu sseu);

+static inline bool intel_context_is_child(struct intel_context *ce)
+{
+ return !!ce->parallel.parent;
+}
+
+static inline bool intel_context_is_parent(struct intel_context *ce)
+{
+ return !!ce->parallel.number_children;
+}
+
+static inline bool intel_context_is_pinned(struct intel_context *ce);
+
+static inline struct intel_context *
+intel_context_to_parent(struct intel_context *ce)
+{
+ if (intel_context_is_child(ce)) {
+ /*
+ * The parent holds ref count to the child so it is always safe
+ * for the parent to access the child, but the child has a
+ * pointer to the parent without a ref. To ensure this is safe
+ * the child should only access the parent pointer while the
+ * parent is pinned.
+ */
+ GEM_BUG_ON(!intel_context_is_pinned(ce->parallel.parent));
+
+ return ce->parallel.parent;
+ } else {
+ return ce;
+ }
+}
+
+void intel_context_bind_parent_child(struct intel_context *parent,
+ struct intel_context *child);
+
+#define for_each_child(parent, ce)\
+ list_for_each_entry(ce, &(parent)->parallel.child_list,\
+ parallel.child_link)
+#define for_each_child_safe(parent, ce, cn)\
+ list_for_each_entry_safe(ce, cn, &(parent)->parallel.child_list,\
+ parallel.child_link)
+
/**
* intel_context_lock_pinned - Stablises the 'pinned' status of the HW context
* @ce - the context
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index 4613d027cbc3..76dfca57cb45 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -220,6 +220,27 @@ struct intel_context {
*/
struct list_head destroyed_link;

+ /** @parallel: sub-structure for parallel submission members */
+ struct {
+ union {
+ /**
+ * @child_list: parent's list of children
+ * contexts, no protection as immutable after context
+ * creation
+ */
+ struct list_head child_list;
+ /**
+ * @child_link: child's link into parent's list of
+ * children
+ */
+ struct list_head child_link;
+ };
+ /** @parent: pointer to parent if child */
+ struct intel_context *parent;
+ /** @number_children: number of children if parent */
+ u8 number_children;
+ } parallel;
+
#ifdef CONFIG_DRM_I915_SELFTEST
/**
* @drop_schedule_enable: Force drop of schedule enable G2H for selftest
--
2.32.0