On Sun, Feb 14, 2016 at 05:36:38PM +0000, Michael Brown wrote:
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.
True - I was just curious since there are similarities between NBP and boot sector (e.g. both are loaded at 7c00) so sometimes the same code can work as both a boot sector and an NBP.
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
Thanks,