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pmbr: Only load the first 545k rather than error out
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Authored by imp on Nov 25 2023, 6:52 PM.
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Summary

It would be nice to have larger boot partitions for ESPs to live in one
day. It's trivial to carve out 5M 10M or 200M when provisioning, but
logistical issues may make it hard to do it after the fact. So only warn
when the partition is > 545k. If we ever grow the boot loader larger
than that, then it will be responsible for loading the rest anyway.

Sponsored by: Netflix

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imp requested review of this revision.Nov 25 2023, 6:52 PM
This revision is now accepted and ready to land.Nov 25 2023, 6:59 PM
stand/i386/pmbr/pmbr.S
234

We're at 438 of 440 usable code bytes here. Better error message for this requires shaving elsewhere.

stand/i386/pmbr/pmbr.S
234

if the larger than 512k partitions are common, this message can just be dropped (and limit documented in gpart bootcode and handbook).

stand/i386/pmbr/pmbr.S
234

Yes indeed. It will be in newer installations....
Still not entirely sure, though, this is a good idea since maybe just have the installer make 2 partitions. Disk space is cheap, and the embedded market doesn't go through bsdinstall... and even if it did, we make 2 parts by default and it can be overridden... Though, there's not a huge amount in the embedded market that's x86, but too low end to have UEFI booting.