drm/amdgpu: always flush the TLB on gfx8

The TLB on GFX8 stores each block of 8 PTEs where any of the valid bits
are set.

Fixes: 5255e14 ("drm/amdgpu: rework TLB flushing")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -793,6 +793,11 @@ int amdgpu_vm_update_range(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 	flush_tlb |= adev->gmc.xgmi.num_physical_nodes &&
 		     adev->ip_versions[GC_HWIP][0] == IP_VERSION(9, 4, 0);
 
+	/*
+	 * On GFX8 and older any 8 PTE block with a valid bit set enters the TLB
+	 */
+	flush_tlb |= adev->ip_versions[GC_HWIP][0] < IP_VERSION(9, 0, 0);
+
 	memset(&params, 0, sizeof(params));
 	params.adev = adev;
 	params.vm = vm;