[PATCH v3 4/5] drm/amdgpu: add SVM attr prefetch/force-trigger functionality

[Junhua Shen <Junhua.Shen@amd.com>]

Add attr_has_prefetch_loc() helper to detect prefetch-loc attributes
and use it to force-trigger migration even when the stored value has
not changed (prefetch is a one-shot command).

Refine attr_change_ctx_trigger() to only fire LOCATION_CHANGE on
prefetch_loc changes, not preferred_loc changes.

Signed-off-by: Junhua Shen <Junhua.Shen@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_svm_attr.c | 34 +++++++++++++++-----
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_attr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_attr.c
index cd972026f39b..52e402c18b0e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_attr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_attr.c
@@ -159,8 +159,7 @@ attr_change_ctx_trigger(const struct amdgpu_svm_attrs *prev_attrs,
 		trigger |= AMDGPU_SVM_ATTR_TRIGGER_PTE_FLAG_CHANGE;
 	if (changed_flags & AMDGPU_SVM_MAPPING_FLAG_MASK)
 		trigger |= AMDGPU_SVM_ATTR_TRIGGER_MAPPING_FLAG_CHANGE;
-	if (prev_attrs->preferred_loc != new_attrs->preferred_loc ||
-	    prev_attrs->prefetch_loc != new_attrs->prefetch_loc)
+	if (prev_attrs->prefetch_loc != new_attrs->prefetch_loc)
 		trigger |= AMDGPU_SVM_ATTR_TRIGGER_LOCATION_CHANGE;
 	if (prev_attrs->granularity != new_attrs->granularity)
 		trigger |= AMDGPU_SVM_ATTR_TRIGGER_GRANULARITY_CHANGE;
@@ -187,9 +186,22 @@ static bool attr_has_access(uint32_t nattr,
 	return false;
 }
 
+static bool attr_has_prefetch_loc(uint32_t nattr,
+				  const struct drm_amdgpu_svm_attribute *attrs)
+{
+	uint32_t i;
+
+	for (i = 0; i < nattr; i++) {
+		if (attrs[i].type == AMDGPU_SVM_ATTR_PREFETCH_LOC)
+			return true;
+	}
+
+	return false;
+}
+
 static struct amdgpu_svm_attr_range *
 attr_alloc_range(unsigned long start,
-			   unsigned long last,
+		   unsigned long last,
 		   const struct amdgpu_svm_attrs *attrs)
 {
 	struct amdgpu_svm_attr_range *range;
@@ -477,23 +489,29 @@ amdgpu_svm_attr_set_existing(struct amdgpu_svm_attr_tree *attr_tree,
 	struct amdgpu_svm_attrs old_attrs;
 	struct amdgpu_svm_attrs new_attrs;
 	uint32_t trigger;
-	bool force_trigger;
+	uint32_t force_trigger = 0;
 
 	lockdep_assert_held(&attr_tree->lock);
 
 	old_attrs = range->attrs;
 
-	/* The attr layer doesn't store the gpu mapped state, and for align with KFD,
-	 * need force trigger range layer to check if gpu mapped.
+	/*
+	 * Force the range layer to act even when the attr value is
+	 * unchanged: ACCESS needs re-check on xnack-off because the
+	 * attr layer has no gpu_mapped state; PREFETCH_LOC is one-shot
+	 * so repeated prefetch must always trigger migration.
 	 */
-	force_trigger = !attr_tree->svm->xnack_enabled && attr_has_access(nattr, attrs);
+	if (!attr_tree->svm->xnack_enabled && attr_has_access(nattr, attrs))
+		force_trigger |= AMDGPU_SVM_ATTR_TRIGGER_ACCESS_CHANGE;
+	if (attr_has_prefetch_loc(nattr, attrs))
+		force_trigger |= AMDGPU_SVM_ATTR_TRIGGER_LOCATION_CHANGE;
 
 	if (attr_same_attrs(range, nattr, attrs)) {
 		if (!force_trigger)
 			return 0;
 
 		amdgpu_svm_attr_change_ctx_set(change, start, last,
-						   AMDGPU_SVM_ATTR_TRIGGER_ACCESS_CHANGE,
+						   force_trigger,
 						   &old_attrs, &old_attrs);
 		return 0;
 	}
-- 
2.34.1