I've replaced grubx64.efi from 16.04 with the one from 17.04 and problem went away. This means that problem is indeed in grub or grub in 16.04 doesn't have needed workarounds for faulty firmwares.
** Changed in: grub2 (Ubuntu) Status: Invalid => Confirmed ** Changed in: grub2 (Ubuntu) Importance: Undecided => High -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1437353 Title: UEFI network boot hangs at grub for adapter 82599ES 10-Gigabit SFI/SFP+ To manage notifications about this bug go to: https://bugs.launchpad.net/maas/+bug/1437353/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs