On 14/02/16 15:53, Michael S. Tsirkin wrote:
That's for execution of a PXE NBP, rather than a (SAN-booted) disk boot sector.
I actually thought the initial post was about iPXE calling NBP (starting at location 07C00h) with a non-zero DS, not about booting from disk.
The initial post mentioned a "boot sector which works just fine when loaded directly from BIOS, but doesn't work when loaded by iPXE". That can only be referring to a disk boot sector, not a PXE NBP. (For a start, the BIOS has no way to directly load a PXE NBP.)
Rephrasing the original question,
It's not a rephrasing; it's an entirely different question.
do you think %DS should be zeroed when NBP is called then?
Not according to the PXE spec.
As far as I can tell, the initial value of %ds is undefined for both a PXE NBP and a BIOS boot sector.
Michael