drm/amdgpu: Update PDEs flush TLB if PTB/PDB moved

Flush TLBs when existing PDEs are updated because a PTB or PDB moved,
but avoids unnecessary TLB flushes when new PDBs or PTBs are added to
the page table, which commonly happens when memory is mapped for the
first time.
Suggested-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NPhilip Yang <Philip.Yang@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -679,6 +679,7 @@ int amdgpu_vm_update_pdes(struct amdgpu_device *adev,
 {
 	struct amdgpu_vm_update_params params;
 	struct amdgpu_vm_bo_base *entry;
+	bool flush_tlb_needed = false;
 	int r, idx;
 
 	if (list_empty(&vm->relocated))
@@ -697,6 +698,9 @@ int amdgpu_vm_update_pdes(struct amdgpu_device *adev,
 		goto error;
 
 	list_for_each_entry(entry, &vm->relocated, vm_status) {
+		/* vm_flush_needed after updating moved PDEs */
+		flush_tlb_needed |= entry->moved;
+
 		r = amdgpu_vm_pde_update(&params, entry);
 		if (r)
 			goto error;
@@ -706,8 +710,8 @@ int amdgpu_vm_update_pdes(struct amdgpu_device *adev,
 	if (r)
 		goto error;
 
-	/* vm_flush_needed after updating PDEs */
-	atomic64_inc(&vm->tlb_seq);
+	if (flush_tlb_needed)
+		atomic64_inc(&vm->tlb_seq);
 
 	while (!list_empty(&vm->relocated)) {
 		entry = list_first_entry(&vm->relocated,