> > The iBFT does not have to be contained within a ROM area.  I'm fairly sure 
> > that this change would break iSCSI-booting via either gPXE or via emBoot's 
> > products, since both will construct the iBFT in base memory (below 640kB).
> > 
> Hmm. We're start scanning an 512k. So the definition of ROM area is a bit
> sloppy here.

The spec states: "The iBFT can be located by:
1. The Low RAM Method. Scan for the table header signature in system memory 
between 512K and 1024K. The scan MUST be done starting at the lower address 
scanning forward to the higher address. When using the Low RAM Method the table 
header must be aligned on a 16-byte boundary."

> But the main point of this patch is that you _must_ _not_ scan the
> entire area. If you do that you crash with buggy BIOSses and with Xen.

I've solved this problem by moving the scanning of the IBFT in the kernel
via a module (look on lkml for 'Add iSCSI iBFT Support". 
I am not sure what you mean by crashing with Xen - that would seem like Xen
has bug in it? 
> And constructing an iBFT without a proper ROM expansion header is ...
> odd.

Yes/No. But unfortunatly this is how the spec is written. Keep also in mind
that the IBFT might be referenced from the ACPI table, which doesn't place
a requirement for a ROM expansion header.

> And as gPXE is open source you surely can add the proper ROM expansion
> header there; shouldn't be too hard to convince emBoot, too.
> Scanning the entire BIOS areas is a definite no-go.

Perhaps it might make sense to provide an argument '--scan-safe' which would
omit certain memory segments which have been found to crash certain buggy 

Thought all of this would become obsolete once the iBFT sysfs patch goes in 
and a variant of this patch would be accepted:


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