Instability issues with NetBSD-9, xen-4.11 and the xbdb backend driver

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	hello.  I'm attempting to run some NetBSD-5.2 guests on a NetBSD-9
BETA xen server and I'm seeing errors from the xbdback_xenbus driver.
These errors cause the guest to panic with the message: 
panic: biodone2 already

This is with NetBSD-9 using xentools411 and xenkernel411

The domU disk is a zfs zvol accessed as a block device on the 
dom0 side of things.

The unknown operation error message is followed by various numbers, perhaps
sequence numbers?
	While this could be a zfs issue, I don't think it is.
Is anyone els seeing errors like these?  

-thanks
-Brian


[   148.550062] xbd backend domain 1 handle 0x1 (1) using event channel 20, protocol x86_64-abi
[   417.880101] xbdb1i1: unknown operation 10
(guest panics at this point...)
[   419.630059] xbd backend: detach device xendisks/viadev for domain 1
[   419.960058] xvif1i0: disconnecting