[PATCH v2 1/1] drm/amdkfd: Add TLB flush after MES queue eviction/suspension

MES (Micro Engine Scheduler) does not perform heavy-weight TLB invalidation
after unmapping queues, unlike HWS which does this automatically. This causes
a race condition where in-flight DMA descriptors can access memory that
has been unmapped, leading to page faults and GPU queue hangs during SVM
page migration.

The issue manifests as KFDSVMRangeTest.MultiThreadMigrationTest/1 failures
on gfx1151 (Ryzen AI MAX) with XNACK mode 1 enabled - the GPU compute queue
hangs with packets submitted but never consumed.

Add kfd_flush_tlb() with TLB_FLUSH_HEAVYWEIGHT in two MES code paths:
1. evict_process_queues_cpsch() - after MES removes queues
2. suspend_queues() - after MES suspends queues and mem_fence completes

This ensures all in-flight memory accesses from unmapped queues are flushed
before memory is freed or migrated.

Testing on gfx1151 shows this reduces failure rate from 100% to approximately
7-10%. The residual failures require further investigation.

Change-Id: Ia83e6af7a66fe2bff56cb62c741728e9a18883e8
Signed-off-by: Priya Hosur <[email protected]>
Reviewed-by: Felix Kuehling <[email protected]>
---
 .../gpu/drm/amd/amdkfd/kfd_device_queue_manager.c   | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
index a23384571193..71c60a42c581 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
@@ -1450,6 +1450,14 @@ static int evict_process_queues_cpsch(struct device_queue_manager *dqm,
 		dqm_evict_mqd_bo(dqm, q);
 	}
 
+	/*
+	 * Heavy-weight TLB flush after MES removes queues to ensure
+	 * in-flight memory accesses complete before memory is freed/migrated.
+	 * HWS does this automatically, MES does not.
+	 */
+	if (dqm->dev->kfd->shared_resources.enable_mes)
+		kfd_flush_tlb(pdd, TLB_FLUSH_HEAVYWEIGHT);
+
 	if (!dqm->dev->kfd->shared_resources.enable_mes) {
 		pdd->last_evict_timestamp = get_jiffies_64();
 		retval = execute_queues_cpsch(dqm,
@@ -3736,8 +3744,11 @@ int suspend_queues(struct kfd_process *p,
 		if (!per_device_suspended) {
 			dqm_unlock(dqm);
 			mutex_unlock(&p->event_mutex);
-			if (total_suspended)
+			if (total_suspended) {
 				amdgpu_amdkfd_debug_mem_fence(dqm->dev->adev);
+				/* Heavy-weight TLB flush after MES suspends queues */
+				kfd_flush_tlb(pdd, TLB_FLUSH_HEAVYWEIGHT);
+			}
 			continue;
 		}
 
-- 
2.43.0