[PATCH 1/2] drm/amdgpu: guarantee bijective mapping of ring ids for LRU

[Andres Rodriguez]

Depending on usage patterns, the current LRU policy may create a
non-injective mapping between userspace ring ids and kernel rings.

This behaviour is undesired as apps that attempt to fill all HW blocks
would be unable to reach some of them.

This change forces the LRU policy to create bijective mappings only.

Signed-off-by: Andres Rodriguez <andresx7 at gmail.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_queue_mgr.c | 15 ++++++++++--
 drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c      | 33 +++++++++++++++++++++------
 drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h      |  4 ++--
 3 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_queue_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_queue_mgr.c
index 054d750..2cffb0e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_queue_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_queue_mgr.c
@@ -108,24 +108,35 @@ static enum amdgpu_ring_type amdgpu_hw_ip_to_ring_type(int hw_ip)
 		DRM_ERROR("Invalid HW IP specified %d\n", hw_ip);
 		return -1;
 	}
 }
 
 static int amdgpu_lru_map(struct amdgpu_device *adev,
 			  struct amdgpu_queue_mapper *mapper,
 			  int user_ring,
 			  struct amdgpu_ring **out_ring)
 {
-	int r;
+	int r, i;
 	int ring_type = amdgpu_hw_ip_to_ring_type(mapper->hw_ip);
+	int ring_blacklist[AMDGPU_MAX_RINGS];
+	struct amdgpu_ring *ring;
+
+	for (i = 0; i < AMDGPU_MAX_RINGS; i++) {
+		ring = mapper->queue_map[i];
+		if (!ring)
+			ring_blacklist[i] = -1;
+		else
+			ring_blacklist[i] = ring->idx;
+	}
 
-	r = amdgpu_ring_lru_get(adev, ring_type, out_ring);
+	r = amdgpu_ring_lru_get(adev, ring_type, ring_blacklist,
+				AMDGPU_MAX_RINGS, out_ring);
 	if (r)
 		return r;
 
 	return amdgpu_update_cached_map(mapper, user_ring, *out_ring);
 }
 
 /**
  * amdgpu_queue_mgr_init - init an amdgpu_queue_mgr struct
  *
  * @adev: amdgpu_device pointer
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
index ca41b3a..0db07b0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -393,46 +393,65 @@ void amdgpu_ring_fini(struct amdgpu_ring *ring)
 	ring->adev->rings[ring->idx] = NULL;
 }
 
 static void amdgpu_ring_lru_touch_locked(struct amdgpu_device *adev,
 					 struct amdgpu_ring *ring)
 {
 	/* list_move_tail handles the case where ring isn't part of the list */
 	list_move_tail(&ring->lru_list, &adev->ring_lru_list);
 }
 
+static bool amdgpu_ring_is_blacklisted(struct amdgpu_ring *ring,
+				       int *blacklist, int num_blacklist)
+{
+	int i;
+
+	for (i = 0; i < num_blacklist; i++) {
+		if (ring->idx == blacklist[i])
+			return true;
+	}
+
+	return false;
+}
+
 /**
  * amdgpu_ring_lru_get - get the least recently used ring for a HW IP block
  *
  * @adev: amdgpu_device pointer
  * @type: amdgpu_ring_type enum
+ * @blacklist: blacklisted ring ids array
+ * @num_blacklist: number of entries in @blacklist
  * @ring: output ring
  *
  * Retrieve the amdgpu_ring structure for the least recently used ring of
  * a specific IP block (all asics).
  * Returns 0 on success, error on failure.
  */
-int amdgpu_ring_lru_get(struct amdgpu_device *adev, int type,
-			struct amdgpu_ring **ring)
+int amdgpu_ring_lru_get(struct amdgpu_device *adev, int type, int *blacklist,
+			int num_blacklist, struct amdgpu_ring **ring)
 {
 	struct amdgpu_ring *entry;
 
 	/* List is sorted in LRU order, find first entry corresponding
 	 * to the desired HW IP */
 	*ring = NULL;
 	spin_lock(&adev->ring_lru_list_lock);
 	list_for_each_entry(entry, &adev->ring_lru_list, lru_list) {
-		if (entry->funcs->type == type) {
-			*ring = entry;
-			amdgpu_ring_lru_touch_locked(adev, *ring);
-			break;
-		}
+		if (entry->funcs->type != type)
+			continue;
+
+		if (amdgpu_ring_is_blacklisted(entry, blacklist, num_blacklist))
+			continue;
+
+		*ring = entry;
+		amdgpu_ring_lru_touch_locked(adev, *ring);
+		break;
 	}
 	spin_unlock(&adev->ring_lru_list_lock);
 
 	if (!*ring) {
 		DRM_ERROR("Ring LRU contains no entries for ring type:%d\n", type);
 		return -EINVAL;
 	}
 
 	return 0;
 }
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
index 2c801a5..811d76a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
@@ -195,15 +195,15 @@ void amdgpu_ring_generic_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib);
 void amdgpu_ring_commit(struct amdgpu_ring *ring);
 void amdgpu_ring_undo(struct amdgpu_ring *ring);
 int amdgpu_ring_priority_get(struct amdgpu_ring *ring,
 			     enum amd_sched_priority priority);
 void amdgpu_ring_priority_put(struct amdgpu_ring *ring,
 			      enum amd_sched_priority priority);
 int amdgpu_ring_init(struct amdgpu_device *adev, struct amdgpu_ring *ring,
 		     unsigned ring_size, struct amdgpu_irq_src *irq_src,
 		     unsigned irq_type);
 void amdgpu_ring_fini(struct amdgpu_ring *ring);
-int amdgpu_ring_lru_get(struct amdgpu_device *adev, int hw_ip,
-			struct amdgpu_ring **ring);
+int amdgpu_ring_lru_get(struct amdgpu_device *adev, int type, int *blacklist,
+			int num_blacklist, struct amdgpu_ring **ring);
 void amdgpu_ring_lru_touch(struct amdgpu_device *adev, struct amdgpu_ring *ring);
 
 #endif
-- 
2.9.3