Intel X710 chips have an internal (on-chip) switch for various SDN purposes.
The internal switch used 0x88a8 to tag frames within the chip itself.
In order to keep the internal switch protected, the chip silently drops all packets with the currently used internal ethertype.
The ixl driver does already contain code to set the internally used ethertype, but this function is not called in any place.
This patch is a quick hack to change the internal switch_tag within the chip. It's only published to move things forward, to help people with run into the same problem (processing 802.1ad, or double tagged frames).
I'm unsure how move this into the normal ixl driver, but do not want to postphone this solution for a real world problem.