guests not starting properly on 7/amd64 dom0 freshly with xen45

["S.P.Zeidler" <spz%serpens.de@localhost>]

Hi,

symptom:
pkgbuild-DOM0# xl create -c /usr/pkg/etc/xen/amd64-nb7
Parsing config from /usr/pkg/etc/xen/amd64-nb7
Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
    2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015
    The NetBSD Foundation, Inc.  All rights reserved.
Copyright (c) 1982, 1986, 1989, 1991, 1993
    The Regents of the University of California.  All rights reserved.

NetBSD 7.0_STABLE (XEN3_DOMU) #1: Sun Dec 27 11:59:09 UTC 2015
	spz%franklin.NetBSD.org@localhost:/home/netbsd/7/amd64/obj/sys/arch/amd64/compile/XEN3_DOMU
total memory = 8192 MB
avail memory = 7923 MB
kern.module.path=/stand/amd64/7.0/modules
mainbus0 (root)
hypervisor0 at mainbus0: Xen version 4.5.1
vcpu0 at hypervisor0: Intel(R) Xeon(R) CPU           L5639  @ 2.13GHz, id 0x206c2
vcpu1 at hypervisor0: Intel(R) Xeon(R) CPU           L5639  @ 2.13GHz, id 0x206c2
vcpu2 at hypervisor0: Intel(R) Xeon(R) CPU           L5639  @ 2.13GHz, id 0x206c2
xenbus0 at hypervisor0: Xen Virtual Bus Interface
xencons0 at hypervisor0: Xen Virtual Console Driver
xenbus: can't get state for device/suspend/event-channel (2)
xbd0 at xenbus0 id 51712: Xen Virtual Block Device Interface
xennet0 at xenbus0 id 0: Xen Virtual Network Interface
xennet0: MAC address 00:16:3e:30:30:61
balloon0 at xenbus0 id 0: Xen Balloon driver
balloon0: current reservation: 8388608 KiB
xennet0: using RX copy mode
xenbus: can't get state for device/suspend/event-channel (2)
balloon0: current reservation: 2097152 pages => target: 2097152 pages
ignore shutdown request: 
xenbus: can't get state for device/suspend/event-channel (2)
[indefinite hang]

if I break into ddb I get:
curlwp 0xffffa0000e9b9860 pid 0.5 lowest kstack 0xffffa001650602c0
Stopped in pid 0.5 (system) at  netbsd:breakpoint+0x5:  leave
breakpoint() at netbsd:breakpoint+0x5
xencons_tty_input() at netbsd:xencons_tty_input+0xb2
xencons_handler() at netbsd:xencons_handler+0x65
intr_biglock_wrapper() at netbsd:intr_biglock_wrapper+0x19
Xresume_xenev6() at netbsd:Xresume_xenev6+0x47
--- interrupt ---
Xspllower() at netbsd:Xspllower+0xe
softint_thread() at netbsd:softint_thread+0x123
ds          5008
es          a09b
fs          53e8
gs          5030
rdi         ffffa0000fea90c0
rsi         ffffffff818e5004
rbp         ffffa00165062ca8
rbx         ffffffff818e5004
rdx         2b
rcx         2b
rax         1
r8          ffffa0000e9b5228
r9          0
r10         ffffa00165062e58
r11         e033
r12         ffffa0000feb5680
r13         ffffffff818e5005
r14         ffffa0000fea90c0
r15         1
rip         ffffffff8012e5bd    breakpoint+0x5
cs          e030
rflags      202
rsp         ffffa00165062ca8
ss          e02b
netbsd:breakpoint+0x5:  leave

I get the same behaviour for guest kernels of all permutations of
amd64/i386 and 6.0,6.1 and 7.0.

funny thing is I got amd64-nb7 to boot up -once- to test the 4.5 disk
specification syntax, but no more after that.

Do I interprete the messages correctly to say that network interface and
disk get found? Any idea how to find out why and where it hangs?

I've seen this hang behaviour previously (if not quite as stubbornly)
with xen 4.2, got the advice to use xm instead and that worked.
xm is not available in 4.5 and 4.2 has been eol'd, so we're a bit
hampered here now.

regards,
	spz
-- 
spz%serpens.de@localhost (S.P.Zeidler)