Panic when connecting USB drive to amd64

Hi,

Excuse the crosspost, I don't know if this is amd64 specific or not.

I have a consistent panic when I connect a 2.5" LaCie 250 GB drive to  
a SuperMicro 6015P-TR. This server is running amd64 with ZFS and I  
want to investigate a way to use ZFS send/receive to external USB  
drives for backup.

Here is the panic message:

Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address	= 0x290
fault code		= supervisor read data, page not present
instruction pointer	= 0x8:0xffffffff803ff8aa
stack pointer	        = 0x10:0xffffffffd72eed70
frame pointer	        = 0x10:0xffffffffd72eedb0
code segment		= base 0x0, limit 0xfffff, type 0x1b
			= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags	= interrupt enabled, resume, IOPL = 0
current process		= 48 (usb3)
[thread pid 48 tid 100047 ]
Stopped at      usb_transfer_complete+0x10a:    movq    0x290(%rax),%rax
db> tr
Tracing pid 48 tid 100047 td 0xffffff00034fe350
usb_transfer_complete() at usb_transfer_complete+0x10a
usbd_start_transfer() at usbd_start_transfer+0x1a1
bus_dmamap_load() at bus_dmamap_load+0x453
usbd_transfer() at usbd_transfer+0xae
usbd_sync_transfer() at usbd_sync_transfer+0xe
usbd_do_request_flags_pipe() at usbd_do_request_flags_pipe+0x96
usbd_do_request_flags() at usbd_do_request_flags+0x25
usbd_get_string_desc() at usbd_get_string_desc+0x88
usbd_get_string() at usbd_get_string+0xcd
usbd_devinfo_vp() at usbd_devinfo_vp+0x80
usbd_devinfo() at usbd_devinfo+0x46
usbd_new_device() at usbd_new_device+0x68b
uhub_explore() at uhub_explore+0x295
usb_discover() at usb_discover+0x38
usb_event_thread() at usb_event_thread+0x9f
fork_exit() at fork_exit+0x12b
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffffffd72efd30, rbp = 0 ---

Here is the dmesg:

Copyright (c) 1992-2008 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
	The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 7.0-PRERELEASE #15: Wed Feb  6 16:07:55 CET 2008
     root_at_mars.altus-escon.com:/usr/obj/usr/src/sys/MARS
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Xeon(R) CPU           E5335  _at_ 2.00GHz (2000.08-MHz K8- 
class CPU)
   Origin = "GenuineIntel"  Id = 0x6f7  Stepping = 7
    
Features 
= 
0xbfebfbff 
< 
FPU 
,VME 
,DE 
,PSE 
,TSC 
,MSR 
,PAE 
,MCE 
,CX8 
,APIC 
,SEP 
,MTRR 
,PGE 
,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
    
Features2 
=0x4e33d<SSE3,RSVD2,MON,DS_CPL,VMX,TM2,SSSE3,CX16,xTPR,PDCM,DCA>
   AMD Features=0x20100800<SYSCALL,NX,LM>
   AMD Features2=0x1<LAHF>
   Cores per package: 4
usable memory = 4280487936 (4082 MB)
avail memory  = 4117889024 (3927 MB)
ACPI APIC Table: <PTLTD  	 APIC  >
FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
  cpu0 (BSP): APIC ID:  0
  cpu1 (AP): APIC ID:  1
  cpu2 (AP): APIC ID:  2
  cpu3 (AP): APIC ID:  3
  cpu4 (AP): APIC ID:  4
  cpu5 (AP): APIC ID:  5
  cpu6 (AP): APIC ID:  6
  cpu7 (AP): APIC ID:  7
ioapic0 <Version 2.0> irqs 0-23 on motherboard
ioapic1 <Version 2.0> irqs 24-47 on motherboard
kbd1 at kbdmux0
ath_hal: 0.9.20.3 (AR5210, AR5211, AR5212, RF5111, RF5112, RF2413,  
RF5413)
acpi0: <PTLTD   RSDT> on motherboard
acpi0: [ITHREAD]
acpi0: Power Button (fixed)
Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
acpi_timer0: <24-bit timer at 3.579545MHz> port 0x1008-0x100b on acpi0
cpu0: <ACPI CPU> on acpi0
p4tcc0: <CPU Frequency Thermal Control> on cpu0
cpu1: <ACPI CPU> on acpi0
p4tcc1: <CPU Frequency Thermal Control> on cpu1
cpu2: <ACPI CPU> on acpi0
p4tcc2: <CPU Frequency Thermal Control> on cpu2
cpu3: <ACPI CPU> on acpi0
p4tcc3: <CPU Frequency Thermal Control> on cpu3
cpu4: <ACPI CPU> on acpi0
p4tcc4: <CPU Frequency Thermal Control> on cpu4
cpu5: <ACPI CPU> on acpi0
p4tcc5: <CPU Frequency Thermal Control> on cpu5
cpu6: <ACPI CPU> on acpi0
p4tcc6: <CPU Frequency Thermal Control> on cpu6
cpu7: <ACPI CPU> on acpi0
p4tcc7: <CPU Frequency Thermal Control> on cpu7
pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
pcib1: <ACPI PCI-PCI bridge> at device 2.0 on pci0
pci1: <ACPI PCI bus> on pcib1
pcib2: <ACPI PCI-PCI bridge> irq 16 at device 0.0 on pci1
pci2: <ACPI PCI bus> on pcib2
pcib3: <ACPI PCI-PCI bridge> irq 16 at device 0.0 on pci2
pci3: <ACPI PCI bus> on pcib3
pcib4: <ACPI PCI-PCI bridge> at device 0.0 on pci3
pci4: <ACPI PCI bus> on pcib4
pcib5: <ACPI PCI-PCI bridge> irq 18 at device 2.0 on pci2
pci5: <ACPI PCI bus> on pcib5
em0: <Intel(R) PRO/1000 Network Connection Version - 6.7.3> port  
0x2000-0x201f mem 0xd8000000-0xd801ffff irq 18 at device 0.0 on pci5
em0: Using MSI interrupt
em0: Ethernet address: 00:30:48:7b:88:7e
em0: [FILTER]
em1: <Intel(R) PRO/1000 Network Connection Version - 6.7.3> port  
0x2020-0x203f mem 0xd8020000-0xd803ffff irq 19 at device 0.1 on pci5
em1: Using MSI interrupt
em1: Ethernet address: 00:30:48:7b:88:7f
em1: [FILTER]
pcib6: <ACPI PCI-PCI bridge> at device 0.3 on pci1
pci6: <ACPI PCI bus> on pcib6
puc0: <NetMos NM9835 Dual UART and 1284 Printer port> port  
0x3030-0x3037,0x3028-0x302f,0x3020-0x3027,0x3018-0x301f, 
0x3010-0x3017,0x3000-0x300f irq 24 at device 1.0 on pci6
puc0: [FILTER]
uart0: <Non-standard ns8250 class UART with FIFOs> on puc0
uart0: [FILTER]
uart1: <Non-standard ns8250 class UART with FIFOs> on puc0
uart1: [FILTER]
ppc0: <Parallel port> on puc0
ppc0: Generic chipset (EPP/NIBBLE) in COMPATIBLE mode
ppbus0: <Parallel port bus> on ppc0
plip0: cannot reserve interrupt, failed.
lpt0: <Printer> on ppbus0
lpt0: Polled port
ppi0: <Parallel I/O> on ppbus0
pcib7: <ACPI PCI-PCI bridge> at device 4.0 on pci0
pci7: <ACPI PCI bus> on pcib7
pcib8: <ACPI PCI-PCI bridge> at device 6.0 on pci0
pci8: <ACPI PCI bus> on pcib8
pci0: <base peripheral> at device 8.0 (no driver attached)
uhci0: <Intel 631XESB/632XESB/3100 USB controller USB-1> port  
0x1800-0x181f irq 17 at device 29.0 on pci0
uhci0: [GIANT-LOCKED]
uhci0: [ITHREAD]
usb0: <Intel 631XESB/632XESB/3100 USB controller USB-1> on uhci0
usb0: USB revision 1.0
uhub0: <Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb0
uhub0: 2 ports with 2 removable, self powered
uhci1: <Intel 631XESB/632XESB/3100 USB controller USB-2> port  
0x1820-0x183f irq 19 at device 29.1 on pci0
uhci1: [GIANT-LOCKED]
uhci1: [ITHREAD]
usb1: <Intel 631XESB/632XESB/3100 USB controller USB-2> on uhci1
usb1: USB revision 1.0
uhub1: <Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb1
uhub1: 2 ports with 2 removable, self powered
uhci2: <Intel 631XESB/632XESB/3100 USB controller USB-3> port  
0x1840-0x185f irq 18 at device 29.2 on pci0
uhci2: [GIANT-LOCKED]
uhci2: [ITHREAD]
usb2: <Intel 631XESB/632XESB/3100 USB controller USB-3> on uhci2
usb2: USB revision 1.0
uhub2: <Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb2
uhub2: 2 ports with 2 removable, self powered
ehci0: <Intel 63XXESB USB 2.0 controller> mem 0xd8500000-0xd85003ff  
irq 17 at device 29.7 on pci0
ehci0: [GIANT-LOCKED]
ehci0: [ITHREAD]
usb3: EHCI version 1.0
usb3: companion controllers, 2 ports each: usb0 usb1 usb2
usb3: <Intel 63XXESB USB 2.0 controller> on ehci0
usb3: USB revision 2.0
uhub3: <Intel EHCI root hub, class 9/0, rev 2.00/1.00, addr 1> on usb3
uhub3: 6 ports with 6 removable, self powered
umass0: <Peppercon AG Multidevice, class 0/0, rev 2.00/0.01, addr 2>  
on uhub3
uhid0: <Peppercon AG Multidevice, class 0/0, rev 2.00/0.01, addr 2> on  
uhub3
ukbd0: <Peppercon AG Multidevice, class 0/0, rev 2.00/0.01, addr 2> on  
uhub3
kbd2 at ukbd0
pcib9: <ACPI PCI-PCI bridge> at device 30.0 on pci0
pci9: <ACPI PCI bus> on pcib9
vgapci0: <VGA-compatible display> port 0x4000-0x40ff mem  
0xd0000000-0xd7ffffff,0xd8220000-0xd822ffff irq 18 at device 1.0 on pci9
em2: <Intel(R) PRO/1000 Network Connection Version - 6.7.3> port  
0x4400-0x443f mem 0xd8200000-0xd821ffff irq 16 at device 2.0 on pci9
em2: Ethernet address: 00:30:48:44:1a:ab
em2: [FILTER]
isab0: <PCI-ISA bridge> at device 31.0 on pci0
isa0: <ISA bus> on isab0
atapci0: <Intel 63XXESB2 UDMA100 controller> port  
0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0x1860-0x186f at device 31.1 on pci0
ata0: <ATA channel 0> on atapci0
ata0: [ITHREAD]
ata1: <ATA channel 1> on atapci0
ata1: [ITHREAD]
atapci1: <Intel 63XXESB2 SATA300 controller> port  
0x1890-0x1897,0x1884-0x1887,0x1888-0x188f,0x1880-0x1883,0x1870-0x187f  
mem 0xd8500400-0xd85007ff irq 19 at device 31.2 on pci0
atapci1: [ITHREAD]
ata2: <ATA channel 0> on atapci1
ata2: [ITHREAD]
ata3: <ATA channel 1> on atapci1
ata3: [ITHREAD]
pci0: <serial bus, SMBus> at device 31.3 (no driver attached)
acpi_button0: <Power Button> on acpi0
atkbdc0: <Keyboard controller (i8042)> port 0x60,0x64 irq 1 on acpi0
atkbd0: <AT Keyboard> irq 1 on atkbdc0
kbd0 at atkbd0
atkbd0: [GIANT-LOCKED]
atkbd0: [ITHREAD]
sio0: configured irq 4 not in bitmap of probed irqs 0
sio0: port may not be enabled
sio0: configured irq 4 not in bitmap of probed irqs 0
sio0: port may not be enabled
sio0: <16550A-compatible COM port> port 0x3f8-0x3ff irq 4 flags 0x10  
on acpi0
sio0: type 16550A, console
sio0: [FILTER]
sio1: configured irq 3 not in bitmap of probed irqs 0
sio1: port may not be enabled
sio1: configured irq 3 not in bitmap of probed irqs 0
sio1: port may not be enabled
sio1: <16550A-compatible COM port> port 0x2f8-0x2ff irq 3 on acpi0
sio1: type 16550A
sio1: [FILTER]
fdc0: <floppy drive controller> port 0x3f0-0x3f5,0x3f7 irq 6 drq 2 on  
acpi0
fdc0: [FILTER]
fd0: <1440-KB 3.5" drive> on fdc0 drive 0
orm0: <ISA Option ROM> at iomem 0xc0000-0xcafff on isa0
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x100>
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on  
isa0
WARNING: ZFS is considered to be an experimental feature in FreeBSD.
Timecounters tick every 1.000 msec
ipfw2 (+ipv6) initialized, divert enabled, rule-based forwarding  
disabled, default to deny, logging limited to 50 packets/entry by  
default
ZFS filesystem version 6
ZFS storage pool version 6
acd0: DMA limited to UDMA33, controller found non-ATA66 cable
acd0: DVDROM <MATSHITADVD-ROM SR-8178/PZ16> at ata0-slave UDMA33
ad4: 143089MB <WDC WD1500ADFD-00NLR5 21.07QR5> at ata2-master SATA150
ad6: 143089MB <WDC WD1500ADFD-00NLR5 21.07QR5> at ata3-master SATA150
SMP: AP CPU #1 Launched!
SMP: AP CPU #3 Launched!
SMP: AP CPU #2 Launched!
SMP: AP CPU #5 Launched!
SMP: AP CPU #4 Launched!
SMP: AP CPU #6 Launched!
SMP: AP CPU #7 Launched!
da0 at umass-sim0 bus 0 target 0 lun 0
da0: <PepperC Virtual Disc 1 0.01> Removable Direct Access SCSI-3 device
da0: 40.000MB/s transfers
da0: Attempt to query device size failed: NOT READY, Medium not present
Trying to mount root from zfs:tank

Please let me know if there is anything I can do to help debug this.  
This is not (yet) a production server, so I can try out various things  
if needed.

With kind regards,
Ben