xbd and large sectors

[Greg Troxel <gdt%lexort.com@localhost>]

Over on netbsd-users@, we have been discussing a problem where a dom0
has a disk with 4K sectors and it is being provided to a domU.  Things
do not really work.  The problem is apparently that the xbd driver is
misrepresenting the sector size, for historical reasons.

The proposal is thus to have xbd represent the logical disk to the
kernel exactly matching how xen presents it, including the sector size.

I admit to not really being 100% clea, and yanking chains to make
progress.  (Yes, I used to be a manager at work....)

So:

  Does anybody think I have the basic facts about what's going on wrong?

  Does anybody think this way forward is a bad idea?

  Does anybody know the xen/xbd code well enough to come up with a
  patch?