[SeaBIOS] Bootorder Failover (Patch)

[Steve Goodrich]

> From: Kevin O'Connor [mailto:kevin at koconnor.net]
> If checking for an MBR is sufficient to determine if the drive is
> "bootable" then I'd suggest adding an option to read and validate the
> MBR in the POST phase prior to assigning a drive id to it.

I had looked into this, but could not trace out the functions/methods that
would allow me to read a single sector from the device.  Can you give me a
pointer on this?

> [...]
> > Why is it not safe to alter the IDMap in the boot phase?  Is it unsafe
to
> > allow it to change before the device has actually booted, or is it only
> > unsafe to change once the device has transferred execution to the OS?
> 
> The BIOS specs call for making the f-segment read-only after the POST
> phase ends.  This is implemented under QEMU (and only on QEMU).  The
> "IDMap" variable (along with all variables marked with VAR16) is
> stored in the f-segment.

What BIOS specs are you referring to?  I don't recall seeing those.

Also, since this is currently targeted at a production coreboot/SeaBIOS
environment, would it be sufficient to make the feature dependent upon the
BIOS being built for coreboot?

Regards,
	-- Steve G.