As has been mentioned earlier, the xhci driver causes the boot process to hang on some machines, including mine. However, it turns out that a single keystroke on the PS/2 keyboard (the USB one had not been probed yet) allowed the boot to continue, and I successfully accessed a USB2 flash drive connected to one of my USB3 ports. I'm guessing then that there is an interrupt being lost somewhere, or perhaps a missing timeout. The hang was occurring shortly after attaching uhub0, as indicated in the dmesg.boot below, and you can see the umass0 device attaching to it afterwards.
Gary Duzan p.s. In the unlikely event that it matters, the kernel is GENERIC, but with IPSEC and IPSEC_ESP enabled in GENERIC.local. === Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 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 6.99.25 (GENERIC) #3: Sat Nov 9 11:08:52 EST 2013 r...@nbsd.xnet.duzan.org:/usr/build/netbsd-current/obj/usr/build/netbsd-current/src/sys/arch/amd64/compile/GENERIC total memory = 12028 MB avail memory = 11663 MB timecounter: Timecounters tick every 10.000 msec timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100 Gigabyte Technology Co., Ltd. GA-880GMA-UD2H ( ) mainbus0 (root) cpu0 at mainbus0 apid 0: AMD Athlon(tm) II X4 640 Processor, id 0x100f53 cpu1 at mainbus0 apid 1: AMD Athlon(tm) II X4 640 Processor, id 0x100f53 cpu2 at mainbus0 apid 2: AMD Athlon(tm) II X4 640 Processor, id 0x100f53 cpu3 at mainbus0 apid 3: AMD Athlon(tm) II X4 640 Processor, id 0x100f53 ioapic0 at mainbus0 apid 2: pa 0xfec00000, version 0x21, 24 pins acpi0 at mainbus0: Intel ACPICA 20110623 acpi0: X/RSDT: OemId <GBT ,GBTUACPI,42302e31>, AslId <GBTU,01010101> acpi0: SCI interrupting at int 9 timecounter: Timecounter "ACPI-Fast" frequency 3579545 Hz quality 1000 hpet0 at acpi0: high precision event timer (mem 0xfed00000-0xfed00400) timecounter: Timecounter "hpet0" frequency 14318180 Hz quality 2000 acpibut0 at acpi0 (PWRB, PNP0C0C): ACPI Power Button SYSR (PNP0C02) at acpi0 not configured PMIO (PNP0C02) at acpi0 not configured attimer1 at acpi0 (TMR, PNP0100): io 0x40-0x43 irq 0 pcppi1 at acpi0 (SPKR, PNP0800): io 0x61 midi0 at pcppi1: PC speaker sysbeep0 at pcppi1 FDC0 (PNP0700) at acpi0 not configured pckbc1 at acpi0 (PS2K, PNP0303) (kbd port): io 0x60,0x64 irq 1 EXPL (PNP0C02) at acpi0 not configured MEM (PNP0C01) at acpi0 not configured acpiwmi0 at acpi0 (AOD, PNP0C14-0): ACPI WMI Interface acpiwmibus at acpiwmi0 not configured attimer1: attached to pcppi1 pckbd0 at pckbc1 (kbd slot) pckbc1: using irq 1 for kbd slot wskbd0 at pckbd0: console keyboard pci0 at mainbus0 bus 0: configuration mode 1 pci0: i/o space, memory space enabled, rd/line, rd/mult, wr/inv ok pchb0 at pci0 dev 0 function 0: vendor 0x1022 product 0x9601 (rev. 0x00) ppb0 at pci0 dev 1 function 0: vendor 0x1022 product 0x9602 (rev. 0x00) pci1 at ppb0 bus 1 pci1: i/o space, memory space enabled vga0 at pci1 dev 5 function 0: vendor 0x1002 product 0x9715 (rev. 0x00) wsdisplay0 at vga0 kbdmux 1: console (80x25, vt100 emulation), using wskbd0 wsmux1: connecting to wsdisplay0 radeondrm0 at vga0: ATI Radeon HD 4250 radeondrm0: Initialized radeon 1.29.0 20080613 hdaudio0 at pci1 dev 5 function 1: HD Audio Controller hdaudio0: interrupting at ioapic0 pin 19 hdafg0 at hdaudio0: ATI RS690/780 HDMI hdafg0: HDMI00 2ch: Digital Out [Jack] hdafg0: 2ch/0ch 44100Hz 48000Hz PCM16 AC3 ppb1 at pci0 dev 9 function 0: vendor 0x1022 product 0x9608 (rev. 0x00) ppb1: PCI Express 2.0 <Root Port of PCI-E Root Complex> x1 @ 5.0Gb/s pci2 at ppb1 bus 2 pci2: i/o space, memory space enabled, rd/line, wr/inv ok xhci0 at pci2 dev 0 function 0: vendor 0x1033 product 0x0194 (rev. 0x03) xhci0: interrupting at ioapic0 pin 17 xhci0: xHCI version 0.96 xhci0: ac64 1 ctxsz 32 xhci0: xECP 500 xhci0: ECR 500: 00000401 xhci0: ECR 510: 03000402 xhci0: SP: 03000402 20425355 00000201 xhci0: ECR 520: 02000002 xhci0: SP: 02000002 20425355 00000203 xhci0: PAGESIZE 0x00000001 xhci0: sc_pgsz 0x00001000 xhci0: sc_maxslots 0x00000020 xhci0: sc_maxspbuf 0 xhci0: eventst: NORMAL_COMPLETION 0000000115822fc0 0xffff8000d291bfc0 1000 xhci0: dcbaa: NORMAL_COMPLETION 0000000115823000 0xffff8000d291c000 1000 xhci0: USBCMD 00000005 usb0 at xhci0: USB revision 2.0 ppb2 at pci0 dev 10 function 0: vendor 0x1022 product 0x9609 (rev. 0x00) ppb2: PCI Express 2.0 <Root Port of PCI-E Root Complex> x1 @ 5.0Gb/s ppb2: link is x1 @ 2.5Gb/s pci3 at ppb2 bus 3 pci3: i/o space, memory space enabled, rd/line, wr/inv ok re0 at pci3 dev 0 function 0: RealTek 8168/8111 PCIe Gigabit Ethernet (rev. 0x06) re0: interrupting at ioapic0 pin 18 re0: Ethernet address xx:xx:xx:xx:xx:xx re0: using 256 tx descriptors rgephy0 at re0 phy 7: RTL8169S/8110S/8211 1000BASE-T media interface, rev. 4 rgephy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT, 1000baseT-FDX, auto ahcisata0 at pci0 dev 17 function 0: vendor 0x1002 product 0x4391 (rev. 0x40) ahcisata0: interrupting at ioapic0 pin 19 ahcisata0: 64-bit DMA ahcisata0: AHCI revision 1.20, 6 ports, 32 slots, CAP 0xf732ff05<PSC,SSC,PMD,SPM,ISS=0x3=Gen3,SCLO,SAL,SALP,SMPS,SSNTF,SNCQ,S64A> atabus0 at ahcisata0 channel 0 atabus1 at ahcisata0 channel 1 atabus2 at ahcisata0 channel 2 atabus3 at ahcisata0 channel 3 atabus4 at ahcisata0 channel 4 atabus5 at ahcisata0 channel 5 ohci0 at pci0 dev 18 function 0: vendor 0x1002 product 0x4397 (rev. 0x00) ohci0: interrupting at ioapic0 pin 18 ohci0: OHCI version 1.0, legacy support usb1 at ohci0: USB revision 1.0 ehci0 at pci0 dev 18 function 2: vendor 0x1002 product 0x4396 (rev. 0x00) ehci0: interrupting at ioapic0 pin 17 ehci0: dropped intr workaround enabled ehci0: EHCI version 1.0 ehci0: companion controller, 5 ports each: ohci0 usb2 at ehci0: USB revision 2.0 ohci1 at pci0 dev 19 function 0: vendor 0x1002 product 0x4397 (rev. 0x00) ohci1: interrupting at ioapic0 pin 18 ohci1: OHCI version 1.0, legacy support usb3 at ohci1: USB revision 1.0 ehci1 at pci0 dev 19 function 2: vendor 0x1002 product 0x4396 (rev. 0x00) ehci1: interrupting at ioapic0 pin 17 ehci1: dropped intr workaround enabled ehci1: EHCI version 1.0 ehci1: companion controller, 5 ports each: ohci1 usb4 at ehci1: USB revision 2.0 piixpm0 at pci0 dev 20 function 0: vendor 0x1002 product 0x4385 (rev. 0x42) piixpm0: polling (SB800) iic0 at piixpm0: I2C bus iic1 at piixpm0: I2C bus iic2 at piixpm0: I2C bus iic3 at piixpm0: I2C bus hdaudio1 at pci0 dev 20 function 2: HD Audio Controller hdaudio1: interrupting at ioapic0 pin 16 hdafg1 at hdaudio1: Realtek ALC892 hdafg1: DAC00 8ch: Speaker [Jack] hdafg1: DAC01 2ch: HP Out [Jack] hdafg1: DIG02 2ch: SPDIF Out [Jack] hdafg1: DIG03 2ch: SPDIF Out [Built-In] hdafg1: ADC04 2ch: Line In [Jack], Mic In [Jack] hdafg1: ADC05 2ch: Mic In [Jack] hdafg1: DIG-In06 2ch: SPDIF In [Jack] hdafg1: 8ch/2ch 32000Hz 44100Hz 48000Hz 88200Hz 96000Hz 192000Hz PCM16 PCM20 PCM24 AC3 audio0 at hdafg1: full duplex, playback, capture, independent pcib0 at pci0 dev 20 function 3: vendor 0x1002 product 0x439d (rev. 0x40) ppb3 at pci0 dev 20 function 4: vendor 0x1002 product 0x4384 (rev. 0x40) pci4 at ppb3 bus 4 pci4: i/o space, memory space enabled fwohci0 at pci4 dev 14 function 0: vendor 0x104c product 0x8024 (rev. 0x00) fwohci0: interrupting at ioapic0 pin 22 fwohci0: OHCI version 1.10 (ROM=0) fwohci0: No. of Isochronous channels is 4. fwohci0: EUI64 00:19:8f:c8:00:1c:6f:65 fwohci0: Phy 1394a available S400, 3 ports. fwohci0: Link S400, max_rec 2048 bytes. ieee1394if0 at fwohci0: IEEE1394 bus fwip0 at ieee1394if0: IP over IEEE1394 fwohci0: Initiate bus reset ohci2 at pci0 dev 20 function 5: vendor 0x1002 product 0x4399 (rev. 0x00) ohci2: interrupting at ioapic0 pin 18 ohci2: OHCI version 1.0, legacy support usb5 at ohci2: USB revision 1.0 ppb4 at pci0 dev 21 function 0: vendor 0x1002 product 0x43a0 (rev. 0x00) ppb4: PCI Express 2.0 <Root Port of PCI-E Root Complex> x1 @ 2.5Gb/s pci5 at ppb4 bus 5 pci5: i/o space, memory space enabled, rd/line, wr/inv ok jmide0 at pci5 dev 0 function 0: vendor 0x197b product 0x2368 (rev. 0x00) jmide0: 1 PATA port jmide0: interrupting at ioapic0 pin 17 jmide0: PCI IDE interface used jmide0: bus-master DMA support present jmide0: primary channel wired to native-PCI mode jmide0: primary channel is PATA atabus6 at jmide0 channel 0 jmide0: secondary channel wired to native-PCI mode jmide0: secondary channel is unused ppb5 at pci0 dev 21 function 1: vendor 0x1002 product 0x43a1 (rev. 0x00) ppb5: PCI Express 2.0 <Root Port of PCI-E Root Complex> x1 @ 2.5Gb/s pci6 at ppb5 bus 6 pci6: i/o space, memory space enabled, rd/line, wr/inv ok ohci3 at pci0 dev 22 function 0: vendor 0x1002 product 0x4397 (rev. 0x00) ohci3: interrupting at ioapic0 pin 18 ohci3: OHCI version 1.0, legacy support usb6 at ohci3: USB revision 1.0 ehci2 at pci0 dev 22 function 2: vendor 0x1002 product 0x4396 (rev. 0x00) ehci2: interrupting at ioapic0 pin 17 ehci2: dropped intr workaround enabled ehci2: EHCI version 1.0 ehci2: companion controller, 4 ports each: ohci3 usb7 at ehci2: USB revision 2.0 pchb1 at pci0 dev 24 function 0: vendor 0x1022 product 0x1200 (rev. 0x00) pchb2 at pci0 dev 24 function 1: vendor 0x1022 product 0x1201 (rev. 0x00) pchb3 at pci0 dev 24 function 2: vendor 0x1022 product 0x1202 (rev. 0x00) amdnb_misc0 at pci0 dev 24 function 3: AMD NB Misc Configuration amdtemp0 at amdnb_misc0: AMD CPU Temperature Sensors (Family10h) pchb4 at pci0 dev 24 function 4: vendor 0x1022 product 0x1204 (rev. 0x00) isa0 at pcib0 fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2 acpicpu0 at cpu0: ACPI CPU acpicpu0: C1: HLT, lat 0 us, pow 0 mW acpicpu0: P0: FFH, lat 4 us, pow 26460 mW, 3000 MHz acpicpu0: P1: FFH, lat 4 us, pow 18590 mW, 2300 MHz acpicpu0: P2: FFH, lat 4 us, pow 15360 mW, 1800 MHz acpicpu0: P3: FFH, lat 4 us, pow 8715 mW, 800 MHz acpicpu1 at cpu1: ACPI CPU acpicpu2 at cpu2: ACPI CPU acpicpu3 at cpu3: ACPI CPU fwohci0: BUS reset fwohci0: node_id=0xc800ffc0, gen=1, CYCLEMASTER mode ieee1394if0: 1 nodes, maxhop <= 0 cable IRM irm(0) (me) ieee1394if0: bus manager 0 xhci0: port 3 status change timecounter: Timecounter "clockinterrupt" frequency 100 Hz quality 0 timecounter: Timecounter "TSC" frequency 3013945600 Hz quality 3000 xhci0: xhci_new_device up 0xfffffe811575c710 portno 0 xhci0: xhci_new_device hub 0xfffffe8115a5f008 xhci0: xhci_new_device hub 0x0 xhci0: xhci_new_device rhport 2 xhci0: xhci_open addr 0 depth 0 port 0 speed 3 uhub0 at usb0: NetBSD xHCI Root Hub, class 9/0, rev 2.00/1.00, addr 0 uhub0: 2 ports with 2 removable, self powered xhci0: xhci_open addr 0 depth 0 port 0 speed 3 # # Hang here until keypress # IPsec: Initialized Security Association Processing. uhub1 at usb1: vendor 0x1002 OHCI root hub, class 9/0, rev 1.00/1.00, addr 1 uhub1: 5 ports with 5 removable, self powered uhub2 at usb2: vendor 0x1002 EHCI root hub, class 9/0, rev 2.00/1.00, addr 1 uhub2: 5 ports with 5 removable, self powered uhub3 at usb3: vendor 0x1002 OHCI root hub, class 9/0, rev 1.00/1.00, addr 1 uhub3: 5 ports with 5 removable, self powered uhub4 at usb4: vendor 0x1002 EHCI root hub, class 9/0, rev 2.00/1.00, addr 1 uhub4: 5 ports with 5 removable, self powered uhub5 at usb5: vendor 0x1002 OHCI root hub, class 9/0, rev 1.00/1.00, addr 1 uhub5: 2 ports with 2 removable, self powered uhub6 at usb6: vendor 0x1002 OHCI root hub, class 9/0, rev 1.00/1.00, addr 1 uhub6: 4 ports with 4 removable, self powered uhub7 at usb7: vendor 0x1002 EHCI root hub, class 9/0, rev 2.00/1.00, addr 1 uhub7: 4 ports with 4 removable, self powered ahcisata0 port 0: device present, speed: 3.0Gb/s ahcisata0 port 1: device present, speed: 1.5Gb/s ahcisata0 port 4: device present, speed: 1.5Gb/s xhci0: root_hub 0x0 fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec xhci0: port 3 status change xhci0: hs port 1 status change ehci0: handing over full speed device on port 1 to ohci0 xhci0: xhci_new_device up 0xfffffe81157934c0 portno 1 xhci0: xhci_new_device hub 0xfffffe8115b81108 xhci0: xhci_new_device hub 0xfffffe8115a5f008 xhci0: xhci_new_device hub 0x0 xhci0: xhci_new_device rhport 3 xhci0: xhci_open addr 0 depth 1 port 1 speed 3 xhci0: xhci_do_command input: 0x0000000000000000 0x00000000 0x00002400 xhci0: xhci_do_command output: 0x0000000115818000 0x01000000 0x01008401 xhci0: dcbaa 0xffff8000d291c008 dc 0000000115c2c000 slot 1 xhci0: xhci_do_command input: 0x0000000115c2e000 0x00000000 0x01002c00 xhci0: xhci_do_command output: 0x0000000115818010 0x01000000 0x01008401 xhci0: xhci_new_device device address 1 wd0 at atabus0 drive 0 wd0: <WDC WD6401AALS-00J7B0> wd0: drive supports 16-sector PIO transfers, LBA48 addressing wd0: 596 GB, 1240341 cyl, 16 head, 63 sec, 512 bytes/sect x 1250263728 sectors xhci0: xhci_new_device bMaxPacketSize 64 xhci0: xhci_update_ep0_mps xhci0: xhci_do_command input: 0x0000000115c2e000 0x00000000 0x01003400 xhci0: xhci_do_command output: 0x0000000115818020 0x01000000 0x01008401 xhci0: xhci_open addr 1 depth 1 port 1 speed 3 umass0 at uhub0 port 1 configuration 1 interface 0 umass0: HP v125w, rev 2.00/1.00, addr 1 umass0: using SCSI over Bulk-Only xhci0: xhci_open addr 1 depth 1 port 1 speed 3 xhci0: xhci_configure_endpoint dci 4 (0x2) xhci0: xhci_do_command input: 0x0000000115c2e000 0x00000000 0x01003000 xhci0: xhci_do_command output: 0x0000000115818030 0x01000000 0x01008401 xhci0: xhci_open addr 1 depth 1 port 1 speed 3 xhci0: xhci_configure_endpoint dci 3 (0x81) xhci0: xhci_do_command input: 0x0000000115c2e000 0x00000000 0x01003000 xhci0: xhci_do_command output: 0x0000000115818040 0x01000000 0x01008401 scsibus0 at umass0: 2 targets, 1 lun per target sd0 at scsibus0 target 0 lun 0: <hp, v125w, 1.00> disk removable wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) wd0(ahcisata0:0:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) (using DMA) wd1 at atabus1 drive 0 sd0: fabricating a geometry sd0: 3819 MB, 3819 cyl, 64 head, 32 sec, 512 bytes/sect x 7823296 sectors sd0: fabricating a geometry wd1: <HITACHI HTS722016K9SA00> wd1: drive supports 16-sector PIO transfers, LBA48 addressing wd1: 149 GB, 310101 cyl, 16 head, 63 sec, 512 bytes/sect x 312581808 sectors wd1: GPT GUID: 15dc2ee4-a0ce-4749-a8b8-b12f351ace02 wd1: bad GPT partition array CRC wd1: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) wd1(ahcisata0:1:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) (using DMA) atapibus0 at atabus4: 1 targets cd0 at atapibus0 drive 0: <ASUS DRW-24B1ST, , 1.01> cdrom removable cd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100) cd0(ahcisata0:4:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100) (using DMA) ehci0: handing over full speed device on port 2 to ohci0 uhub8 at uhub4 port 1: vendor 0x05e3 USB2.0 Hub, class 9/0, rev 2.00/77.63, addr 2 uhub8: single transaction translator uhub8: 4 ports with 4 removable, self powered uscanner0 at uhub1 port 1 uscanner0: Hewlett-Packard HP ScanJet 5200C, rev 1.00/1.00, addr 2 uhub9 at uhub2 port 5: vendor 0x05e3 USB2.0 Hub, class 9/0, rev 2.00/7.02, addr 2 uhub9: single transaction translator uhub9: 4 ports with 4 removable, self powered uhub10 at uhub8 port 4: vendor 0x05e3 USB2.0 Hub, class 9/0, rev 2.00/77.63, addr 3 uhub10: single transaction translator uhub10: 4 ports with 4 removable, self powered uhidev0 at uhub9 port 3 configuration 1 interface 0 uhidev0: vendor 0x0461 USB Optical Mouse, rev 2.00/2.00, addr 3, iclass 3/1 ums0 at uhidev0: 3 buttons, W and Z dirs wsmouse0 at ums0 mux 0 umass1 at uhub10 port 1 configuration 1 interface 0 umass1: Kingston FCR-HS219/1 Mobile Reader, rev 2.00/97.38, addr 4 umass1: using SCSI over Bulk-Only scsibus1 at umass1: 2 targets, 4 luns per target sd1 at scsibus1 target 0 lun 0: <Kingston, FCR-HS219/1, 9738> disk removable sd1: drive offline sd2 at scsibus1 target 0 lun 1: <Kingston, FCR-HS219/1, 9738> disk removable sd2: drive offline sd3 at scsibus1 target 0 lun 2: <Kingston, FCR-HS219/1, 9738> disk removable sd3: drive offline sd4 at scsibus1 target 0 lun 3: <Kingston, FCR-HS219/1, 9738> disk removable sd4: drive offline uhidev1 at uhub9 port 4 configuration 1 interface 0 uhidev1: Unicomp Endura Keyboard, rev 1.10/2.0c, addr 4, iclass 3/1 ukbd0 at uhidev1: 8 modifier keys, 6 key codes umass2 at uhub10 port 4 configuration 1 interface 0 umass2: Sunplus Innovation Technology. USB to Serial-ATA bridge, rev 2.00/1.0f, addr 5 umass2: using SCSI over Bulk-Only scsibus2 at umass2: 2 targets, 1 lun per target sd5 at scsibus2 target 0 lun 0: <SPIF301, USB2SATA Bridge, 0108> disk removable sd5: drive offline wskbd1 at ukbd0 mux 1 wskbd1: connecting to wsdisplay0 Kernelized RAIDframe activated pad0: outputs: 44100Hz, 16-bit, stereo audio1 at pad0: half duplex, playback, capture boot device: wd1 root on wd1a dumps on wd1b root file system type: ffs wsdisplay0: screen 1 added (80x25, vt100 emulation) wsdisplay0: screen 2 added (80x25, vt100 emulation) wsdisplay0: screen 3 added (80x25, vt100 emulation) wsdisplay0: screen 4 added (80x25, vt100 emulation)