[PATCH 2/2] drm/xe: skip resv fence wait in xe_svm_invalidate if no ranges are bound

[aquiles]

xe_svm_invalidate() waited on the VM's reservation object fences before
processing MMU notifier events, even when no range in the affected
address region had active GPU bindings (tile_present == 0).

Add a pre-scan over the affected ranges and skip dma_resv_wait_timeout()
entirely when none require invalidation. This avoids stalling CPU reclaim
for the common case where MMU notifier events fire on unbound SVM ranges,
which is frequent on UMA systems under memory pressure.

Signed-off-by: aquiles <achillezongo07@xxxxxxxxx>
---
 drivers/gpu/drm/xe/xe_svm.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
index e1651e70c..5d071bab3 100644
--- a/drivers/gpu/drm/xe/xe_svm.c
+++ b/drivers/gpu/drm/xe/xe_svm.c
@@ -233,6 +233,7 @@ static void xe_svm_invalidate(struct drm_gpusvm *gpusvm,
 	ktime_t start = xe_gt_stats_ktime_get();
 	u64 adj_start = mmu_range->start, adj_end = mmu_range->end;
 	u8 tile_mask = 0, id;
+	bool needs_inval = false;
 	long err;
 
 	xe_svm_assert_in_notifier(vm);
@@ -258,11 +259,22 @@ static void xe_svm_invalidate(struct drm_gpusvm *gpusvm,
 	if (xe_vm_is_closed(vm))
 		goto range_notifier_event_end;
 
-	/*
-	 * XXX: Less than ideal to always wait on VM's resv slots if an
-	 * invalidation is not required. Could walk range list twice to figure
-	 * out if an invalidations is need, but also not ideal.
-	 */
+	/* Pre-scan: skip fence wait if no range has active GPU bindings. */
+
+	r = first;
+	drm_gpusvm_for_each_range(r, notifier, adj_start, adj_end) {
+		struct xe_svm_range *range = to_xe_range(r);
+
+		if (!range->base.pages.flags.unmapped && range->tile_present) {
+			needs_inval = true;
+			break;
+		}
+
+	}
+	if (!needs_inval)
+		goto range_notifier_event_end;
+
+
 	err = dma_resv_wait_timeout(xe_vm_resv(vm),
 				    DMA_RESV_USAGE_BOOKKEEP,
 				    false, MAX_SCHEDULE_TIMEOUT);
-- 
2.54.0