drm/amdgpu: rework how we handle TLB fences

From Alex Deucher
f0d3bb6f5125c69ce872a7574afd6d9e1f7ea349 in linux-6.18.y/6.18.32
69c5fbd2b93b5ced77c6e79afe83371bca84c788 in mainline linux

sys/dev/pci/drm/amd/amdgpu/amdgpu_vm.c

@@ -1126,7 +1126,10 @@ amdgpu_vm_tlb_flush(struct amdgpu_vm_update_params *params,
 	}
 
 	/* Prepare a TLB flush fence to be attached to PTs */
-	if (!params->unlocked) {
+	/* The check for need_tlb_fence should be dropped once we
+	 * sort out the issues with KIQ/MES TLB invalidation timeouts.
+	 */
+	if (!params->unlocked && vm->need_tlb_fence) {
 		amdgpu_vm_tlb_fence_create(params->adev, vm, fence);
 
 		/* Makes sure no PD/PT is freed before the flush */
@@ -2672,6 +2675,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 	ttm_lru_bulk_move_init(&vm->lru_bulk_move);
 
 	vm->is_compute_context = false;
+	vm->need_tlb_fence = amdgpu_userq_enabled(&adev->ddev);
 
 	vm->use_cpu_for_update = !!(adev->vm_manager.vm_update_mode &
 				    AMDGPU_VM_USE_CPU_FOR_GFX);
@@ -2809,6 +2813,7 @@ int amdgpu_vm_make_compute(struct amdgpu_device *adev, struct amdgpu_vm *vm)
 	dma_fence_put(vm->last_update);
 	vm->last_update = dma_fence_get_stub();
 	vm->is_compute_context = true;
+	vm->need_tlb_fence = true;
 
 unreserve_bo:
 	amdgpu_bo_unreserve(vm->root.bo);

sys/dev/pci/drm/amd/amdgpu/amdgpu_vm.h

@@ -449,6 +449,8 @@ struct amdgpu_vm {
 	struct ttm_lru_bulk_move lru_bulk_move;
 	/* Flag to indicate if VM is used for compute */
 	bool			is_compute_context;
+	/* Flag to indicate if VM needs a TLB fence (KFD or KGD) */
+	bool			need_tlb_fence;
 
 	/* Memory partition number, -1 means any partition */
 	int8_t			mem_id;