Large file copy seems to cause dom0 kernel panic

["Stephen M. Jones" <smj%cirr.com@localhost>]

I am able to get a consistent dom0 kernel panic while copying large files
across local disks (2-5GB in size).  The files are not associated with any
running domu.  If the dom0 is in single user mode I am able to copy the 
same files without causing a kernel panic.

xenkernel33-3.3.2nb4 Xen 3.3.2 Kernel
NetBSD vps 5.1.0_PATCH NetBSD 5.1.0_PATCH (XEN3_DOM0) #0: Wed Sep 28 05:40:32 
UTC 2011  root@:/var/netbsd/usr/src/sys/arch/amd64/compile/XEN3_DOM0 amd64

here are a couple of panics:

xenbus: can't get state for backend/vbd/5/51712 (2)
uvm_fault(0xffffffff80c03fc0, 0xffffffff81400000, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff804fb653 cs e030 rflags 10286 cr2  
ffffffff81400078 cpl 0 rsp ffffa0006a873110
panic: trap
Begin traceback...
uvm_fault(0xffffa0006a8485d8, 0x0, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff804f53bc cs e030 rflags 10246 cr2  0 cpl 0 rsp 
ffffa0006a872cc0
panic: trap
Faulted in mid-traceback; aborting...
dump to dev 0,1 not possible
panic: wdc_exec_command: polled command not done
Faulted in mid-traceback; aborting...
dump to dev 0,1 not possible
panic: wdc_exec_command: polled command not done
Faulted in mid-traceback; aborting...
dump to dev 0,1 not possible


xbd backend: detach device vnd30d for domain 5
xbd backend: detach device vnd50d for domain 5
Sep 29 04:56:01 vps xenbackendd[318]: Failed to read 
/local/domain/0/backend/console/5/0/script (No such file or directory)
uvm_fault(0xffffffff80c03fc0, 0xffffffff81400000, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff804fb653 cs e030 rflags 10282 cr2  
ffffffff81400058 cpl 0 rsp ffffa0006aaef110
panic: trap
Begin traceback...
uvm_fault(0xffffa0006a91e8c0, 0x0, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff804f53bc cs e030 rflags 10246 cr2  0 cpl 0 rsp 
ffffa0006aaeecc0
panic: trap
Faulted in mid-traceback; aborting...
dump to dev 0,1 not possible
panic: wdc_exec_command: polled command not done
Faulted in mid-traceback; aborting...
dump to dev 0,1 not possible
panic: wdc_exec_command: polled command not done
Faulted in mid-traceback; aborting...
dump to dev 0,1 not possible
rebooting...
(XEN) Domain 0 shutdown: rebooting machine.