Qemu-upstream with Xen

[Roger Pau Monné <roger.pau%entel.upc.edu@localhost>]

Hello,

I'm trying to get qemu-upstream (present in xen-unstable) to work with
NetBSD, but there seems to be some problem with the vga shared memory
mapping. Qemu starts correctly and allocates vram memory, but it seems
like the call to xc_domain_add_to_physmap doesn't work correctly, and
when Qemu tries to write to that memory region after the mapping it
gets a segfault.

When debugging Qemu with gdb I've realized that after calling
xc_domain_add_to_physmap the memory region is no longer "available" to
Qemu, but the same happens with old Qemu and it works fine (gdb tells
me I cannot access the memory region, but Qemu seems to be able to
write to it without problems).

Qemu-upstream uses a different memory region for vram than the old
one, so I don't know if that might be the cause of the error, but I
cannot find any kind of limitation to the memory area/size one can map
using xc_domain_add_to_physmap at least on sys/arch/xen/xen/privcmd.c.

Maybe someone more experienced with this can give me a hand. Any help
on how to track/solve this is appreciated.

Thanks, Roger.