seltests/net: devlink port split failing in H-5.11 KVM kernels (Error sending command: devlink -j dev show)

Got the following selftests/net failure in Hirsute, cycle sru-20210531 :

03:28:51 DEBUG| [stdout] # selftests: net: devlink_port_split.py
03:28:51 DEBUG| [stdout] # Error sending command: devlink -j dev show
03:28:51 DEBUG| [stdout] #
03:28:51 DEBUG| [stdout] # Failed to connect to devlink Netlink
03:28:51 DEBUG| [stdout] #
03:28:51 DEBUG| [stdout] # Traceback (most recent call last):
03:28:51 DEBUG| [stdout] # File "/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/net/./devlink_port_split.py", line 277, in <module>
03:28:51 DEBUG| [stdout] # main()
03:28:51 DEBUG| [stdout] # File "/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/net/./devlink_port_split.py", line 239, in main
03:28:51 DEBUG| [stdout] # assert stderr == ""
03:28:51 DEBUG| [stdout] # AssertionError
03:28:51 DEBUG| [stdout] not ok 43 selftests: net: devlink_port_split.py # exit=1

Noticed that it also failed in previous cycles (I'm not sure why I couldn't find a report...)