7.0_BETA crashes on some Amazon EC2 instances

[Jeff Rizzo <riz%NetBSD.org@localhost>]

I'm currently trying to get 7.0_BETA images up on Amazon EC2, but I'm 
seeing a very high rate of crashes.  (~50% during boot).  Has anyone 
else seen this?

Here's a crash:

NetBSD 7.0_BETA (XEN3_DOMU.201410252300Z)
total memory = 615 MB
avail memory = 586 MB
kern.module.path=/stand/amd64/7.0/modules
mainbus0 (root)
hypervisor0 at mainbus0: Xen version 3.4.3.amazon
vcpu0 at hypervisor0: Intel(R) Xeon(R) CPU E5-2650 0 @ 2.00GHz, id 0x206d7
xenbus0 at hypervisor0: Xen Virtual Bus Interface
xencons0 at hypervisor0: Xen Virtual Console Driver
xbd0 at xenbus0 id 2049: Xen Virtual Block Device Interface
xbd1 at xenbus0 id 2050: Xen Virtual Block Device Interface
xennet0 at xenbus0 id 0: Xen Virtual Network Interface
xennet0: MAC address 22:00:0a:5b:94:c4
balloon0 at xenbus0 id 0: Xen Balloon driver
balloon0: current reservation: 629760 KiB
xennet0: using RX copy mode
boot device: xbd1
root on xbd1a dumps on xbd1b
balloon0: current reservation: 157440 pages => target: 157440 pages
root file system type: ffs
fatal privileged instruction fault in supervisor mode
trap type 0 code 0 rip ffffffff8012e3a2 cs e030 rflags 10246 cr2 
7f7ff781db1c ilevel 8 rsp ffffa0001c7feec8
curlwp 0xffffa000017c4120 pid 14.1 lowest kstack 0xffffa0001c7fc2c0
kernel: privileged instruction fault trap, code=0
Stopped in pid 14.1 (ps) at     netbsd:xrstor+0xa:      fxsavel
xrstor() at netbsd:xrstor+0xa
ds          4120
es          95c0
fs          0
gs          d000
rdi         ffffa0001c7fc080
rsi         7
rbp         ffffa0001c7feef0
rbx         ffffa000017c4120
rdx         0
rcx         0
rax         7
r8          3ff
r9          7f7fffffdc50
r10         7f7ff7c0c19a
r11         246
r12         ffffffff805d4600    cpu_info_primary
r13         ffffa0001c7fc000
r14         0
r15         4001c8
rip         ffffffff8012e3a2    xrstor+0xa
cs          e030
rflags      10246
rsp         ffffa0001c7feec8
ss          e02b
netbsd:xrstor+0xa:      fxsavel
db{0}>

For comparison, here's a working boot:

NetBSD 7.0_BETA (XEN3_DOMU.201410252300Z)
total memory = 615 MB
avail memory = 586 MB
kern.module.path=/stand/amd64/7.0/modules
mainbus0 (root)
hypervisor0 at mainbus0: Xen version 3.4.3.amazon
vcpu0 at hypervisor0: Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz, 
id 0x206c2
xenbus0 at hypervisor0: Xen Virtual Bus Interface
xencons0 at hypervisor0: Xen Virtual Console Driver
xbd0 at xenbus0 id 2049: Xen Virtual Block Device Interface
xbd1 at xenbus0 id 2050: Xen Virtual Block Device Interface
xennet0 at xenbus0 id 0: Xen Virtual Network Interface
xennet0: MAC address 22:00:0a:f9:10:84
balloon0 at xenbus0 id 0: Xen Balloon driver
balloon0: current reservation: 629760 KiB
xennet0: using RX copy mode
boot device: xbd1
root on xbd1a dumps on xbd1b
balloon0: current reservation: 157440 pages => target: 157440 pages
root file system type: ffs
Mon Oct 27 21:17:35 UTC 2014
rcorder: Circular dependency on provision `LOGIN' in file `/etc/rc.d/sshd'.
rcorder exited with code 1
Starting root file system check:
/dev/rxbd1a: file system is clean; not checking

There seems to be some correlation between vcpu and crashes.  I've seen 
these vcpus boot to completion:

vcpu0 at hypervisor0: Intel(R) Xeon(R) CPU           E5645  @ 2.40GHz, 
id 0x206c2
vcpu0 at hypervisor0: Intel(R) Xeon(R) CPU E5-2670 v2 @ 2.50GHz, id 0x306e4

And these seem to always crash:

vcpu0 at hypervisor0: Intel(R) Xeon(R) CPU E5-2650 0 @ 2.00GHz, id 0x206d7


...does anyone have more info?

Thanks,
+j