Bug 859829

(In reply to comment #0)
> Description of problem:
> 
> guestmount on centos 6.2 hand on when execute this command:
> guestmount --ro -a /var/lib/nova/instances/instance-0000000d/disk -m
> /dev/vda1 /tmp/tmpssRjL9ln -v
> 
> Version-Release number of selected component (if applicable):
> rpm -qa | grep libguest
> libguestfs-tools-c-1.16.19-1.el6.x86_64
> libguestfs-tools-1.16.19-1.el6.x86_64
> libguestfs-winsupport-1.0-7.el6.x86_64
> libguestfs-1.16.19-1.el6.x86_64
> 
> 
> here is all output of libguestfs-test-tool:
> ===== Test starts here =====
> LIBGUESTFS_DEBUG=1
> TMPDIR=(not set)
> libguestfs: new guestfs handle 0x73c700
> library version: 1.16.19rhel=6,release=1.el6
> guestfs_get_append: (null)
> guestfs_get_attach_method: appliance
> guestfs_get_autosync: 1
> guestfs_get_direct: 0
> guestfs_get_memsize: 500
> guestfs_get_network: 0
> guestfs_get_path: /usr/lib64/guestfs
> guestfs_get_pgroup: 0
> guestfs_get_qemu: /usr/libexec/qemu-kvm
> guestfs_get_recovery_proc: 1
> guestfs_get_selinux: 0
> guestfs_get_smp: 1
> guestfs_get_trace: 0
> guestfs_get_verbose: 1
> host_cpu: x86_64
> Launching appliance, timeout set to 600 seconds.
> libguestfs: [00000ms] febootstrap-supermin-helper --verbose -f checksum
> '/usr/lib64/guestfs/supermin.d' x86_64
> supermin helper [00000ms] whitelist = (not specified), host_cpu = x86_64,
> kernel = (null), initrd = (null), appliance = (null)
> supermin helper [00000ms] inputs[0] = /usr/lib64/guestfs/supermin.d
> checking modpath /lib/modules/2.6.32-220.el6.x86_64 is a directory
> picked vmlinuz-2.6.32-220.el6.x86_64 because modpath
> /lib/modules/2.6.32-220.el6.x86_64 exists
> supermin helper [00000ms] finished creating kernel
> supermin helper [00000ms] visiting /usr/lib64/guestfs/supermin.d
> supermin helper [00000ms] visiting /usr/lib64/guestfs/supermin.d/base.img
> supermin helper [00000ms] visiting /usr/lib64/guestfs/supermin.d/daemon.img
> supermin helper [00000ms] visiting /usr/lib64/guestfs/supermin.d/hostfiles
> supermin helper [00029ms] visiting /usr/lib64/guestfs/supermin.d/init.img
> supermin helper [00029ms] visiting
> /usr/lib64/guestfs/supermin.d/ntfs.hostfiles
> supermin helper [00029ms] visiting /usr/lib64/guestfs/supermin.d/ntfs.img
> supermin helper [00029ms] adding kernel modules
> supermin helper [00162ms] finished creating appliance
> libguestfs: [00168ms] begin building supermin appliance
> libguestfs: [00168ms] run febootstrap-supermin-helper
> libguestfs: [00168ms] febootstrap-supermin-helper --verbose -f ext2
> /usr/lib64/guestfs/supermin.d x86_64 /var/tmp/guestfs.uvRdty/kernel
> /var/tmp/guestfs.uvRdty/initrd /var/tmp/guestfs.uvRdty/root
> supermin helper [00000ms] whitelist = (not specified), host_cpu = x86_64,
> kernel = /var/tmp/guestfs.uvRdty/kernel, initrd =
> /var/tmp/guestfs.uvRdty/initrd, appliance = /var/tmp/guestfs.uvRdty/root
> supermin helper [00000ms] inputs[0] = /usr/lib64/guestfs/supermin.d
> checking modpath /lib/modules/2.6.32-220.el6.x86_64 is a directory
> picked vmlinuz-2.6.32-220.el6.x86_64 because modpath
> /lib/modules/2.6.32-220.el6.x86_64 exists
> supermin helper [00000ms] finished creating kernel
> supermin helper [00238ms] finished mke2fs
> supermin helper [00239ms] visiting /usr/lib64/guestfs/supermin.d
> supermin helper [00239ms] visiting /usr/lib64/guestfs/supermin.d/base.img
> supermin helper [03016ms] visiting /usr/lib64/guestfs/supermin.d/daemon.img
> supermin helper [03019ms] visiting /usr/lib64/guestfs/supermin.d/hostfiles
> supermin helper [04939ms] visiting /usr/lib64/guestfs/supermin.d/init.img
> supermin helper [04940ms] visiting
> /usr/lib64/guestfs/supermin.d/ntfs.hostfiles
> supermin helper [04942ms] visiting /usr/lib64/guestfs/supermin.d/ntfs.img
> supermin helper [04981ms] adding kernel modules
> supermin helper [06591ms] closing ext2 filesystem
> supermin helper [07255ms] finished creating appliance
> libguestfs: [07427ms] finished building supermin appliance
> libguestfs: [07546ms] begin testing qemu features
> libguestfs: [07562ms] finished testing qemu features
> libguestfs: accept_from_daemon: 0x73c700 g->state = 1
> [07563ms] /usr/libexec/qemu-kvm \
>     -global virtio-blk-pci.scsi=off \
>     -drive
> file=/tmp/libguestfs-test-tool-sda-KfSUZ2,cache=off,format=raw,if=virtio \
>     -nodefconfig \
>     -machine accel=kvm:tcg \
>     -nodefaults \
>     -nographic \
>     -m 500 \
>     -no-reboot \
>     -no-hpet \
>     -device virtio-serial \
>     -serial stdio \
>     -chardev socket,path=/tmp/libguestfsSNkayN/guestfsd.sock,id=channel0 \
>     -device virtserialport,chardev=channel0,name=org.libguestfs.channel.0 \
>     -kernel /var/tmp/.guestfs-0/kernel.13092 \
>     -initrd /var/tmp/.guestfs-0/initrd.13092 \
>     -append 'panic=1 console=ttyS0 udevtimeout=300 no_timer_check acpi=off
> printk.time=1 cgroup_disable=memory selinux=0 guestfs_verbose=1 TERM=xterm '
> \
>     -drive
> file=/var/tmp/.guestfs-0/root.13092,snapshot=on,if=virtio,
> cache=unsafeInitializing cgroup subsys cpuset
> Initializing cgroup subsys cpu
> Linux version 2.6.32-220.el6.x86_64 (mockbuild.dev.centos.org)
> (gcc version 4.4.6 20110731 (Red Hat 4.4.6-3) (GCC) ) #1 SMP Tue Dec 6
> 19:48:22 GMT 2011
> Command line: panic=1 console=ttyS0 udevtimeout=300 no_timer_check acpi=off
> printk.time=1 cgroup_disable=memory selinux=0 guestfs_verbose=1 TERM=xterm 
> KERNEL supported cpus:
>   Intel GenuineIntel
>   AMD AuthenticAMD
>   Centaur CentaurHauls
> BIOS-provided physical RAM map:
>  BIOS-e820: 0000000000000000 - 000000000009bc00 (usable)
>  BIOS-e820: 000000000009bc00 - 00000000000a0000 (reserved)
>  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
>  BIOS-e820: 0000000000100000 - 000000001f3fd000 (usable)
>  BIOS-e820: 000000001f3fd000 - 000000001f400000 (reserved)
>  BIOS-e820: 00000000feffc000 - 00000000ff000000 (reserved)
>  BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
> DMI 2.4 present.
> SMBIOS version 2.4 @ 0xFDA50
> last_pfn = 0x1f3fd max_arch_pfn = 0x400000000
> PAT not supported by CPU.
> init_memory_mapping: 0000000000000000-000000001f3fd000
> RAMDISK: 1f1b2000 - 1f3ef800
> No NUMA configuration found
> Faking a node at 0000000000000000-000000001f3fd000
> Bootmem setup node 0 0000000000000000-000000001f3fd000
>   NODE_DATA [0000000000009000 - 000000000003cfff]
>   bootmap [000000000003d000 -  0000000000040e7f] pages 4
> (7 early reservations) ==> bootmem [0000000000 - 001f3fd000]
>   #0 [0000000000 - 0000001000]   BIOS data page ==> [0000000000 - 0000001000]
>   #1 [0000006000 - 0000008000]       TRAMPOLINE ==> [0000006000 - 0000008000]
>   #2 [0001000000 - 000200c7e4]    TEXT DATA BSS ==> [0001000000 - 000200c7e4]
>   #3 [001f1b2000 - 001f3ef800]          RAMDISK ==> [001f1b2000 - 001f3ef800]
>   #4 [000009bc00 - 0000100000]    BIOS reserved ==> [000009bc00 - 0000100000]
>   #5 [000200d000 - 000200d051]              BRK ==> [000200d000 - 000200d051]
>   #6 [0000008000 - 0000009000]          PGTABLE ==> [0000008000 - 0000009000]
> found SMP MP-table at [ffff8800000fda70] fda70
> kvm-clock: Using msrs 4b564d01 and 4b564d00
> kvm-clock: cpu 0, msr 0:1c1df41, boot clock
> Zone PFN ranges:
>   DMA      0x00000001 -> 0x00001000
>   DMA32    0x00001000 -> 0x00100000
>   Normal   0x00100000 -> 0x00100000
> Movable zone start PFN for each node
> early_node_map[2] active PFN ranges
>     0: 0x00000001 -> 0x0000009b
>     0: 0x00000100 -> 0x0001f3fd
> SFI: Simple Firmware Interface v0.7 http://simplefirmware.org
> Intel MultiProcessor Specification v1.4
> MPTABLE: OEM ID: BOCHSCPU
> MPTABLE: Product ID: 0.1         
> MPTABLE: APIC at: 0xFEE00000
> Processor #0 (Bootup-CPU)
> I/O APIC #1 Version 17 at 0xFEC00000.
> Processors: 1
> SMP: Allowing 1 CPUs, 0 hotplug CPUs
> PM: Registered nosave memory: 000000000009b000 - 000000000009c000
> PM: Registered nosave memory: 000000000009c000 - 00000000000a0000
> PM: Registered nosave memory: 00000000000a0000 - 00000000000f0000
> PM: Registered nosave memory: 00000000000f0000 - 0000000000100000
> Allocating PCI resources starting at 1f400000 (gap: 1f400000:dfbfc000)
> Booting paravirtualized kernel on KVM
> NR_CPUS:4096 nr_cpumask_bits:1 nr_cpu_ids:1 nr_node_ids:1
> PERCPU: Embedded 30 pages/cpu @ffff880002200000 s92696 r8192 d21992 u2097152
> pcpu-alloc: s92696 r8192 d21992 u2097152 alloc=1*2097152
> pcpu-alloc: [0] 0 
> kvm-clock: cpu 0, msr 0:2215f41, primary cpu clock
> Built 1 zonelists in Node order, mobility grouping on.  Total pages: 126041
> Policy zone: DMA32
> Kernel command line: panic=1 console=ttyS0 udevtimeout=300 no_timer_check
> acpi=off printk.time=1 cgroup_disable=memory selinux=0 guestfs_verbose=1
> TERM=xterm 
> [    0.000000] Disabling memory control group subsystem
> [    0.000000] PID hash table entries: 2048 (order: 2, 16384 bytes)
> [    0.000000] Checking aperture...
> [    0.000000] No AGP bridge found
> [    0.000000] Memory: 484048k/511988k available (5084k kernel code, 408k
> absent, 27532k reserved, 7229k data, 1244k init)
> [    0.000000] Hierarchical RCU implementation.
> [    0.000000] NR_IRQS:33024 nr_irqs:256
> [    0.000000] Console: colour *CGA 80x25
> [    0.000000] console [ttyS0] enabled
> [    0.000000] Detected 1999.956 MHz processor.
> [    0.001999] Calibrating delay loop (skipped) preset value.. 3999.91
> BogoMIPS (lpj=1999956)
> [    0.002382] pid_max: default: 32768 minimum: 301
> [    0.003294] Security Framework initialized
> [    0.004020] SELinux:  Disabled at boot.
> [    0.005157] Dentry cache hash table entries: 65536 (order: 7, 524288
> bytes)
> [    0.007030] Inode-cache hash table entries: 32768 (order: 6, 262144 bytes)
> [    0.008103] Mount-cache hash table entries: 256
> [    0.009193] Initializing cgroup subsys ns
> [    0.010018] Initializing cgroup subsys cpuacct
> [    0.010588] Initializing cgroup subsys memory
> [    0.011033] Initializing cgroup subsys devices
> [    0.012014] Initializing cgroup subsys freezer
> [    0.012607] Initializing cgroup subsys net_cls
> [    0.013012] Initializing cgroup subsys blkio
> [    0.014021] Initializing cgroup subsys perf_event
> [    0.015407] mce: CPU supports 10 MCE banks
> [    0.016055] alternatives: switching to unfair spinlock
> [    0.021769] SMP alternatives: switching to UP code
> [    0.049574] Freeing SMP alternatives: 33k freed
> [    0.050052] ftrace: converting mcount calls to 0f 1f 44 00 00
> [    0.051015] ftrace: allocating 20776 entries in 82 pages
> [    0.053046] Setting APIC routing to flat
> [    0.054999] ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
> [    0.055002] CPU0: Intel QEMU Virtual CPU version 1.0,1 stepping 03
> [    0.158330] Performance Events: unsupported p6 CPU model 2 no PMU driver,
> software events only.
> [    0.158999] NMI watchdog disabled (cpu0): hardware events not enabled
> [    0.159014] Brought up 1 CPUs
> [    0.159242] Total of 1 processors activated (3999.91 BogoMIPS).
> [    0.160201] devtmpfs: initialized
> [    0.163136] regulator: core version 0.5
> [    0.163467] NET: Registered protocol family 16
> [    0.164881] PCI: Using configuration type 1 for base access
> [    0.166024] bio: create slab <bio-0> at 0
> [    0.166393] ACPI: Interpreter disabled.
> [    0.166682] vgaarb: loaded
> [    0.167076] SCSI subsystem initialized
> [    0.167401] usbcore: registered new interface driver usbfs
> [    0.168014] usbcore: registered new interface driver hub
> [    0.168398] usbcore: registered new device driver usb
> [    0.169017] PCI: Probing PCI hardware
> [    0.170074] pci 0000:00:01.3: quirk: region b000-b03f claimed by PIIX4
> ACPI
> [    0.170606] pci 0000:00:01.3: quirk: region b100-b10f claimed by PIIX4 SMB
> [    0.178455] pci 0000:00:01.0: PIIX/ICH IRQ router [8086:7000]
> [    0.179464] NetLabel: Initializing
> [    0.180007] NetLabel:  domain hash size = 128
> [    0.181005] NetLabel:  protocols = UNLABELED CIPSOv4
> [    0.181717] NetLabel:  unlabeled traffic allowed by default
> [    0.182110] Switching to clocksource kvm-clock
> [    0.200540] pnp: PnP ACPI: disabled
> [    0.201565] NET: Registered protocol family 2
> [    0.202358] IP route cache hash table entries: 4096 (order: 3, 32768
> bytes)
> [    0.204428] TCP established hash table entries: 16384 (order: 6, 262144
> bytes)
> [    0.205608] TCP bind hash table entries: 16384 (order: 6, 262144 bytes)
> [    0.206663] TCP: Hash tables configured (established 16384 bind 16384)
> [    0.207654] TCP reno registered
> [    0.208263] NET: Registered protocol family 1
> [    0.208883] pci 0000:00:00.0: Limiting direct PCI/PCI transfers
> [    0.209863] pci 0000:00:01.0: PIIX3: Enabling Passive Release
> [    0.210753] pci 0000:00:01.0: Activating ISA DMA hang workarounds
> [    0.211737] Trying to unpack rootfs image as initramfs...
> [    0.215208] Freeing initrd memory: 2294k freed
> [    0.216368] platform rtc_cmos: registered platform RTC device (no PNP
> device found)
> [    0.218065] audit: initializing netlink socket (disabled)
> [    0.218863] type=2000 audit(1348469658.218:1): initialized
> [    0.236241] HugeTLB registered 2 MB page size, pre-allocated 0 pages
> [    0.238236] VFS: Disk quotas dquot_6.5.2
> [    0.238830] Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
> [    0.239922] msgmni has been set to 949
> [    0.240872] alg: No test for stdrng (krng)
> [    0.241562] ksign: Installing public key data
> [    0.242233] Loading keyring
> [    0.242651] - Added public key 3A25C209CBB1D210
> [    0.243342] - User ID: CentOS (Kernel Module GPG key)
> [    0.244132] Block layer SCSI generic (bsg) driver version 0.4 loaded
> (major 252)
> [    0.245232] io scheduler noop registered
> [    0.245764] io scheduler anticipatory registered
> [    0.246477] io scheduler deadline registered
> [    0.247176] io scheduler cfq registered (default)
> [    0.248023] pci_hotplug: PCI Hot Plug PCI Core version: 0.5
> [    0.248898] pciehp: PCI Express Hot Plug Controller Driver version: 0.4
> [    0.249892] acpiphp: ACPI Hot Plug PCI Controller Driver version: 0.5
> [    0.252965] Non-volatile memory driver v1.3
> [    0.253646] Linux agpgart interface v0.103
> [    0.254365] crash memory driver: version 1.1
> [    0.254947] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
> \xffffffff[    0.501876] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> [    0.504833] brd: module loaded
> [    0.506250] loop: module loaded
> [    0.506775] input: Macintosh mouse button emulation as
> /devices/virtual/input/input0
> [    0.507983] Fixed MDIO Bus: probed
> [    0.508653] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
> [    0.509661] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
> [    0.510603] uhci_hcd: USB Universal Host Controller Interface driver
> [    0.511641] PNP: No PS/2 controller found. Probing ports directly.
> [    0.513671] serio: i8042 KBD port at 0x60,0x64 irq 1
> [    0.514441] serio: i8042 AUX port at 0x60,0x64 irq 12
> [    0.515338] mice: PS/2 mouse device common for all mice
> [    0.516680] input: AT Translated Set 2 keyboard as
> /devices/platform/i8042/serio0/input/input1
> [    0.518377] rtc_cmos rtc_cmos: rtc core: registered rtc_cmos as rtc0
> [    0.519501] rtc0: alarms up to one day, 114 bytes nvram
> [    0.524275] cpuidle: using governor ladder
> [    0.524845] cpuidle: using governor menu
> [    0.527168] usbcore: registered new interface driver hiddev
> [    0.527950] usbcore: registered new interface driver usbhid
> [    0.528785] usbhid: v2.6:USB HID core driver
> [    0.529542] TCP cubic registered
> [    0.529980] Initializing XFRM netlink socket
> [    0.530670] NET: Registered protocol family 17
> [    0.531514] registered taskstats version 1
> [    0.532645] rtc_cmos rtc_cmos: setting system clock to 2012-09-24
> 06:54:17 UTC (1348469657)
> [    0.533894] Initalizing network drop monitor service
> [    0.534710] Freeing unused kernel memory: 1244k freed
> [    0.535975] Write protecting the kernel read-only data: 10240k
> [    0.537236] Freeing unused kernel memory: 1040k freed
> [    0.538578] Freeing unused kernel memory: 1760k freed
> febootstrap: mounting /proc
> febootstrap: uptime: 0.54 0.29
> febootstrap: ext2 mini initrd starting up: 3.12 zlib
> febootstrap: mounting /sys
> febootstrap: internal insmod libcrc32c.ko
> febootstrap: internal insmod crc32c-intel.ko
> insmod: init_module: crc32c-intel.ko: No such device
> febootstrap: internal insmod crc-itu-t.ko
> febootstrap: internal insmod crc-t10dif.ko
> febootstrap: internal insmod crc-ccitt.ko
> febootstrap: internal insmod crc7.ko
> febootstrap: internal insmod mbcache.ko
> febootstrap: internal insmod cdrom.ko
> febootstrap: internal insmod sr_mod.ko
> febootstrap: internal insmod ata_piix.ko
> [    0.597355] scsi0 : ata_piix
> [    0.597895] scsi1 : ata_piix
> [    0.598477] ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xc0a0 irq 14
> [    0.599485] ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xc0a8 irq 15
> febootstrap: internal insmod scsi_transport_spi.ko
> febootstrap: internal insmod sym53c8xx.ko
> febootstrap: internal insmod sd_mod.ko
> febootstrap: internal insmod virtio_ring.ko
> febootstrap: internal insmod virtio.ko
> febootstrap: internal insmod virtio-rng.ko
> febootstrap: internal insmod virtio_console.ko
> febootstrap: internal insmod virtio_blk.ko
> febootstrap: internal insmod virtio_net.ko
> febootstrap: internal insmod virtio_pci.ko
> [    0.824919] virtio-pci 0000:00:02.0: PCI->APIC IRQ transform: INT A ->
> IRQ 10
> [    0.843722] virtio-pci 0000:00:03.0: PCI->APIC IRQ transform: INT A ->
> IRQ 11
> [    0.846426]  vda: unknown partition table
> [    0.848246] virtio-pci 0000:00:04.0: PCI->APIC IRQ transform: INT A ->
> IRQ 11
> [    0.850418]  vdb:
> [    0.962778] input: ImExPS/2 Generic Explorer Mouse as
> /devices/platform/i8042/serio1/input/input2
> 
> and hang on here

after two minutes, it show this:
[  240.233218] INFO: task init:1 blocked for more than 120 seconds.
[  240.234297] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  240.235582] init          D 0000000000000000     0     1      0 0x00000000
[  240.236802]  ffff88001e9ab5d8 0000000000000082 ffff880000000000 00000000c7fdf800
[  240.238269]  0000000100000000 ffff88001e9316e0 000000000000038c ffffffffaf9ff2a5
[  240.239619]  ffff88001e9a9a78 ffff88001e9abfd8 000000000000f4e8 ffff88001e9a9a78
[  240.240978] Call Trace:
[  240.241561]  [<ffffffff8109b809>] ? ktime_get_ts+0xa9/0xe0
[  240.242560]  [<ffffffff81110b10>] ? sync_page+0x0/0x50
[  240.243525]  [<ffffffff814ed1c3>] io_schedule+0x73/0xc0
[  240.244510]  [<ffffffff81110b4d>] sync_page+0x3d/0x50
[  240.245378]  [<ffffffff814eda2a>] __wait_on_bit_lock+0x5a/0xc0
[  240.246345]  [<ffffffff811ae7b0>] ? blkdev_get_block+0x0/0x70
[  240.247295]  [<ffffffff81110ae7>] __lock_page+0x67/0x70
[  240.248176]  [<ffffffff81090c30>] ? wake_bit_function+0x0/0x50
[  240.249022]  [<ffffffff811129ea>] do_read_cache_page+0xca/0x180
[  240.250004]  [<ffffffff811af760>] ? blkdev_readpage+0x0/0x20
[  240.250960]  [<ffffffff81112ae9>] read_cache_page_async+0x19/0x20
[  240.251960]  [<ffffffff81112afe>] read_cache_page+0xe/0x20
[  240.252889]  [<ffffffff811e6ee0>] read_dev_sector+0x30/0xa0
[  240.253836]  [<ffffffff811e9c11>] read_lba+0x101/0x110
[  240.254678]  [<ffffffff811ea105>] find_valid_gpt+0xd5/0x6b0
[  240.255581]  [<ffffffff8106a9d1>] ? vprintk+0x1d1/0x4f0
[  240.256438]  [<ffffffff811ea75f>] efi_partition+0x7f/0x370
[  240.257298]  [<ffffffff814ec42d>] ? printk+0x41/0x44
[  240.258113]  [<ffffffff811e7c17>] rescan_partitions+0x1a7/0x470
[  240.258983]  [<ffffffff811afec6>] __blkdev_get+0x1b6/0x3c0
[  240.259876]  [<ffffffff811b00e0>] blkdev_get+0x10/0x20
[  240.260701]  [<ffffffff811e70a5>] register_disk+0x155/0x170
[  240.261598]  [<ffffffff81258816>] add_disk+0xa6/0x160
[  240.262447]  [<ffffffffa00adf6b>] virtblk_probe+0x49f/0x55c [virtio_blk]
[  240.263493]  [<ffffffffa00ad170>] ? blk_done+0x0/0x110 [virtio_blk]
[  240.264485]  [<ffffffffa0095370>] virtio_dev_probe+0xd0/0x110 [virtio]
[  240.265532]  [<ffffffff81346630>] driver_probe_device+0xa0/0x2a0
[  240.266490]  [<ffffffff813468e0>] ? __device_attach+0x0/0x60
[  240.267373]  [<ffffffff81346933>] __device_attach+0x53/0x60
[  240.268230]  [<ffffffff81345514>] bus_for_each_drv+0x64/0x90
[  240.269111]  [<ffffffff813469fc>] device_attach+0x8c/0xa0
[  240.269910]  [<ffffffff813452bd>] bus_probe_device+0x2d/0x50
[  240.270838]  [<ffffffff813437b7>] device_add+0x527/0x650
[  240.271702]  [<ffffffff8134c96b>] ? pm_runtime_init+0xcb/0xe0
[  240.272653]  [<ffffffff813438fe>] device_register+0x1e/0x30
[  240.273577]  [<ffffffffa00954ab>] register_virtio_device+0x7b/0xa0 [virtio]
[  240.274653]  [<ffffffff81285ae0>] ? pci_request_selected_regions+0x10/0x20
[  240.275726]  [<ffffffffa00c0003>] virtio_pci_probe+0x17c/0x1c4 [virtio_pci]
[  240.276825]  [<ffffffff81289aa7>] local_pci_probe+0x17/0x20
[  240.277726]  [<ffffffff8128ac91>] pci_device_probe+0x101/0x120
[  240.278679]  [<ffffffff81346492>] ? driver_sysfs_add+0x62/0x90
[  240.279630]  [<ffffffff81346630>] driver_probe_device+0xa0/0x2a0
[  240.280601]  [<ffffffff813468db>] __driver_attach+0xab/0xb0
[  240.281508]  [<ffffffff81346830>] ? __driver_attach+0x0/0xb0
[  240.282434]  [<ffffffff81345894>] bus_for_each_dev+0x64/0x90
[  240.283309]  [<ffffffff813463ce>] driver_attach+0x1e/0x20
[  240.284156]  [<ffffffff81345cd0>] bus_add_driver+0x200/0x300
[  240.284991]  [<ffffffff81346c06>] driver_register+0x76/0x140
[  240.285925]  [<ffffffff814f2525>] ? notifier_call_chain+0x55/0x80
[  240.286899]  [<ffffffff8128aef6>] __pci_register_driver+0x56/0xd0
[  240.287855]  [<ffffffff81096e75>] ? __blocking_notifier_call_chain+0x65/0x80
[  240.288954]  [<ffffffffa00c3000>] ? virtio_pci_init+0x0/0x20 [virtio_pci]
[  240.290009]  [<ffffffffa00c301e>] virtio_pci_init+0x1e/0x20 [virtio_pci]
[  240.291058]  [<ffffffff8100204c>] do_one_initcall+0x3c/0x1d0
[  240.291877]  [<ffffffff810af641>] sys_init_module+0xe1/0x250
[  240.292805]  [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b

I think we saw this bug during development of RHEL 6.3.

You say this is CentOS 6.2, but the libguestfs package is
from CentOS 6.3.  What version of CentOS?  Is it fully up
to date?

Also:

rpm -q kernel qemu-kvm seabios

[After discussing this with the bug reporter on IRC]

Cause by a later qemu.  The bug was fixed by reverting
qemu back to the version what ships with CentOS.