In the BIOS world, 99% of serial consoles were a hackish thing that mirrored the VGA text output to the serial console, hence lilo/grub "just worked", and then the kernel could DTRT with a console= given to it. I'm guessing EFI is doing things more correctly here, which leads to grub actually needing serial drivers all of a sudden.
If grub's detecting serial consoles based on the ACPI console node's setting, I see exactly zero danger in enabling this globally. In fact, if it's doing so, I suspect we can also go one better and propagate that detection down via a conditional in grub.cfg, if we really want to be clever (may require patches to upstream, may not be as simple as it sounds, YMMV, no promises, warranty void upon reading this comment).
In the BIOS world, 99% of serial consoles were a hackish thing that mirrored the VGA text output to the serial console, hence lilo/grub "just worked", and then the kernel could DTRT with a console= given to it. I'm guessing EFI is doing things more correctly here, which leads to grub actually needing serial drivers all of a sudden.
If grub's detecting serial consoles based on the ACPI console node's setting, I see exactly zero danger in enabling this globally. In fact, if it's doing so, I suspect we can also go one better and propagate that detection down via a conditional in grub.cfg, if we really want to be clever (may require patches to upstream, may not be as simple as it sounds, YMMV, no promises, warranty void upon reading this comment).