hw/xen: Add basic ring handling to xenstore

Extract requests, return ENOSYS to all of them. This is enough to allow
older Linux guests to boot, as they need *something* back but it doesn't
matter much what.

A full implementation of a single-tentant internal XenStore copy-on-write
tree with transactions and watches is waiting in the wings to be sent in
a subsequent round of patches along with hooking up the actual PV disk
back end in qemu, but this is enough to get guests booting for now.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
1 file changed