[SeaBIOS] Bootorder Failover (Patch)

[Gleb Natapov]

On Tue, Jul 17, 2012 at 06:43:01AM -0600, Steve Goodrich wrote:
> > 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?
> 
If it makes sense for QEMU why add the limitation?

--
			Gleb.