From 2146b7bcb7d9b47e4538f13f04ef3c94cd7076a3 Mon Sep 17 00:00:00 2001
From: Felix Kuehling <Felix.Kuehling@amd.com>
Date: Tue, 7 Dec 2021 21:04:06 -0500
Subject: drm/amdkfd: Don't split unchanged SVM ranges
Git-commit: 4853cbcd94bdd654e94aa40ae718efcf5b6ae57a
Patch-mainline: v5.17-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

If an existing SVM range overlaps an svm_range_set_attr call, we would
normally split it in order to update only the overlapping part.
However, if the attributes of the existing range would not be changed
splitting it is unnecessary.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 07342630740e..c178d56361d6 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -1855,18 +1855,24 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size,
 	node = interval_tree_iter_first(&svms->objects, start, last);
 	while (node) {
 		struct interval_tree_node *next;
-		struct svm_range *old;
 		unsigned long next_start;
 
 		pr_debug("found overlap node [0x%lx 0x%lx]\n", node->start,
 			 node->last);
 
-		old = container_of(node, struct svm_range, it_node);
+		prange = container_of(node, struct svm_range, it_node);
 		next = interval_tree_iter_next(node, start, last);
 		next_start = min(node->last, last) + 1;
 
-		if (node->start < start || node->last > last) {
-			/* node intersects the updated range, clone+split it */
+		if (svm_range_is_same_attrs(p, prange, nattr, attrs)) {
+			/* nothing to do */
+		} else if (node->start < start || node->last > last) {
+			/* node intersects the update range and its attributes
+			 * will change. Clone and split it, apply updates only
+			 * to the overlapping part
+			 */
+			struct svm_range *old = prange;
+
 			prange = svm_range_clone(old);
 			if (!prange) {
 				r = -ENOMEM;
@@ -1875,6 +1881,7 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size,
 
 			list_add(&old->remove_list, remove_list);
 			list_add(&prange->insert_list, insert_list);
+			list_add(&prange->update_list, update_list);
 
 			if (node->start < start) {
 				pr_debug("change old range start\n");
@@ -1894,16 +1901,12 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size,
 			/* The node is contained within start..last,
 			 * just update it
 			 */
-			prange = old;
-		}
-
-		if (!svm_range_is_same_attrs(p, prange, nattr, attrs))
 			list_add(&prange->update_list, update_list);
+		}
 
 		/* insert a new node if needed */
 		if (node->start > start) {
-			prange = svm_range_new(prange->svms, start,
-					       node->start - 1);
+			prange = svm_range_new(svms, start, node->start - 1);
 			if (!prange) {
 				r = -ENOMEM;
 				goto out;
-- 
2.38.1