How to Debug read operation on hda

[Daniel Castro]

Greeting,

As part of the xen code for PV-Drivers in Seabios I am trying to boot
from a PV drive. The two ends are connected, and it should be working,
but when I try to boot from the harddrive it fails.
Inside the code I treat the cdrom as a drive, except I register it in
seabios with the cdrom function, but also it fails to boot from cdrom
with Error 003.
This could mean that maybe I am adding the drives incorrectly, or that
my read/write opertaion is wrong.

Since the operation runs in 16bit how can I debug it to see what is being done?

Thanks for the answers.

Daniel