"xen_emul_unplug=unnecessary,all".

[    0.000000] Initializing cgroup subsys cpu
[    0.000000] Linux version 2.6.37-7-virtual (buildd@yellow) (gcc version 4.5.2 (Ubuntu/Linaro 4.5.1-10ubuntu3) ) #19-Ubuntu SMP Wed Dec 1 02:15:20 UTC 2010 (Ubuntu 2.6.37-7.19-virtual 2.6.37-rc3)
[    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-2.6.37-7-virtual root=UUID=f7f04f87-04f3-488b-a6ae-014ce5d63850 ro xen_emul_unplug=unnecessary console=ttyS0
[    0.000000] BIOS-provided physical RAM map:
[    0.000000]  BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
--
[    0.000000] NX (Execute Disable) protection: active
[    0.000000] DMI 2.4 present.
[    0.000000] DMI: /HVM domU, BIOS 3.3.1 02/02/2009
[    0.000000] Hypervisor detected: Xen HVM
[    0.000000] Xen version 3.3.
[    0.000000] Xen Platform PCI: unrecognised magic value
[    0.000000] HVMOP_pagetable_dying not supported
[    0.000000] e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved)
[    0.000000] e820 remove range: 00000000000a0000 - 0000000000100000 (usable)
--
[    0.000000] kernel direct mapping tables up to 1fff7000 @ 1fff4000-1fff7000
[    0.000000] RAMDISK: 1f348000 - 1f799000
[    0.000000] ACPI: RSDP 00000000000ea010 00024 (v02    Xen)
[    0.000000] ACPI: XSDT 000000001fff8b70 00034 (v01    Xen      HVM 00000000 HVML 00000000)
[    0.000000] ACPI: FACP 000000001fff8a00 000F4 (v04    Xen      HVM 00000000 HVML 00000000)
[    0.000000] ACPI: DSDT 000000001fff7840 01132 (v02    Xen      HVM 00000000 INTL 20060707)
[    0.000000] ACPI: FACS 000000001fff7800 00040
[    0.000000] ACPI: APIC 000000001fff8b00 00068 (v02    Xen      HVM 00000000 HVML 00000000)
[    0.000000] ACPI: Local APIC address 0xfee00000
[    0.000000] No NUMA configuration found
--
[    0.000000] PM: Registered nosave memory: 00000000000e0000 - 0000000000100000
[    0.000000] Allocating PCI resources starting at 20000000 (gap: 20000000:e0000000)
[    0.000000] Booting paravirtualized kernel on Xen
[    0.000000] setup_percpu: NR_CPUS:64 nr_cpumask_bits:64 nr_cpu_ids:1 nr_node_ids:1
[    0.000000] PERCPU: Embedded 28 pages/cpu @ffff88001fc00000 s83712 r8192 d22784 u2097152
--
[    0.000000] Built 1 zonelists in Node order, mobility grouping on. Total pages: 129152
[    0.000000] Policy zone: DMA32
[    0.000000] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-2.6.37-7-virtual root=UUID=f7f04f87-04f3-488b-a6ae-014ce5d63850 ro xen_emul_unplug=unnecessary console=ttyS0
[    0.000000] PID hash table entries: 2048 (order: 2, 16384 bytes)
[    0.000000] Checking aperture...
--
[    0.821839] Fixed MDIO Bus: probed
[    0.823360] PPP generic driver version 2.4.2
[    0.825496] Initialising Xen virtual ethernet driver.
[    0.827998] tun: Universal TUN/TAP device driver, 1.6
[    0.830247] tun: (C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>
--
[    2.791086] xen-platform-pci 0000:00:03.0: PCI INT A -> GSI 28 (level, low) -> IRQ 28
[    2.798695] Grant table initialized
[    2.889459] blkfront device/vbd/51712 num-ring-pages 1 nr_ents 32.
[    2.897163] blkfront: sda: barriers disabled
[    2.900483] ------------[ cut here ]------------
[    2.900608] WARNING: at /build/buildd/linux-2.6.37/fs/sysfs/dir.c:451 sysfs_add_one+0xd8/0x150()
[    2.900616] Hardware name: HVM domU
[    2.900618] sysfs: cannot create duplicate filename '/class/block/sda'
[    2.900619] Modules linked in: platform_pci acpiphp floppy 8139too 8139cp
[    2.900656] Pid: 10, comm: xenwatch Not tainted 2.6.37-7-virtual #19-Ubuntu
[    2.900659] Call Trace:
[    2.900668]  [<ffffffff8106623f>] warn_slowpath_common+0x7f/0xc0
[    2.900671]  [<ffffffff81066336>] warn_slowpath_fmt+0x46/0x50
[    2.900674]  [<ffffffff811d4608>] sysfs_add_one+0xd8/0x150
[    2.900677]  [<ffffffff811d4fbb>] sysfs_do_create_link+0x12b/0x210
[    2.900680]  [<ffffffff811d50b3>] sysfs_create_link+0x13/0x20
[    2.900717]  [<ffffffff813ab923>] device_add_class_symlinks+0xb3/0xd0
[    2.900721]  [<ffffffff813acd98>] device_add+0x248/0x410
[    2.900725]  [<ffffffff811cb2b1>] register_disk+0x41/0x170
[    2.900748]  [<ffffffff812cbf26>] add_disk+0xa6/0x160
[    2.900753]  [<ffffffff813c9a60>] blkfront_connect+0x120/0x1e0
[    2.900756]  [<ffffffff813c9b60>] blkback_changed+0x40/0x50
[    2.900761]  [<ffffffff8136d420>] otherend_changed+0xb0/0xc0
[    2.900763]  [<ffffffff8136b9b6>] xenwatch_thread+0xb6/0x170
[    2.900768]  [<ffffffff81087da0>] ? autoremove_wake_function+0x0/0x40
[    2.900771]  [<ffffffff8136b900>] ? xenwatch_thread+0x0/0x170
[    2.900773]  [<ffffffff81087676>] kthread+0x96/0xa0
[    2.900777]  [<ffffffff8100cee4>] kernel_thread_helper+0x4/0x10
[    2.900780]  [<ffffffff810875e0>] ? kthread+0x0/0xa0
[    2.900783]  [<ffffffff8100cee0>] ? kernel_thread_helper+0x0/0x10
[    2.900785] ---[ end trace d4f9aa3628762311 ]---
[    2.900811] ------------[ cut here ]------------
[    2.902999] kernel BUG at /build/buildd/linux-2.6.37/fs/sysfs/group.c:65!
[    2.906099] invalid opcode: 0000 [#1] SMP
[    2.908061] last sysfs file: /sys/devices/pci0000:00/0000:00:03.0/uevent
[    2.910028] CPU 0
[    2.910028] Modules linked in: platform_pci acpiphp floppy 8139too 8139cp
[    2.910028]
[    2.910028] Pid: 10, comm: xenwatch Tainted: G        W 2.6.37-7-virtual #19-Ubuntu /HVM domU
[    2.910028] RIP: 0010:[<ffffffff811d64b7>]  [<ffffffff811d64b7>] internal_create_group+0x187/0x1a0
[    2.910028] RSP: 0018:ffff88001f9b3ce0  EFLAGS: 00010246
[    2.910028] RAX: 00000000ffffffef RBX: ffff88001c4f3800 RCX: ffff88001cf70900
[    2.910028] RDX: ffffffff81a1faa0 RSI: 0000000000000000 RDI: ffff88001c4f3870
[    2.910028] RBP: ffff88001f9b3d30 R08: 000000000000000d R09: 000000000000000b
[    2.910028] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88001c6368e0
[    2.910028] R13: ffff88001c4f3860 R14: ffffffff81a1faa0 R15: 0000000000000000
[    2.910028] FS:  00007f1c2c9e4700(0000) GS:ffff88001fc00000(0000) knlGS:0000000000000000
[    2.910028] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[    2.910028] CR2: 00007fe87eb2c1d8 CR3: 000000001cd33000 CR4: 00000000000006f0
[    2.910028] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    2.910028] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[    2.910028] Process xenwatch (pid: 10, threadinfo ffff88001f9b2000, task ffff88001f9a5b00)
[    2.910028] Stack:
[    2.910028]  ffff88001f9b3d40 ffff88001c4f3870 000000303a323032 ffff88001f9b3d50
[    2.910028]  ffff88001f9b3d10 ffff88001c4f3800 ffff88001c6368e0 ffff88001c4f3860
[    2.910028]  ffff88001dfc1de0 ffff88001c4f3800 ffff88001f9b3d40 ffffffff811d6503
[    2.910028] Call Trace:
[    2.910028]  [<ffffffff811d6503>] sysfs_create_group+0x13/0x20
[    2.910028]  [<ffffffff810f7174>] blk_trace_init_sysfs+0x14/0x20
[    2.910028]  [<ffffffff812c5fa0>] blk_register_queue+0x40/0x110
[    2.910028]  [<ffffffff812cbf2e>] add_disk+0xae/0x160
[    2.910028]  [<ffffffff813c9a60>] blkfront_connect+0x120/0x1e0
[    2.910028]  [<ffffffff813c9b60>] blkback_changed+0x40/0x50
[    2.910028]  [<ffffffff8136d420>] otherend_changed+0xb0/0xc0
[    2.910028]  [<ffffffff8136b9b6>] xenwatch_thread+0xb6/0x170
[    2.910028]  [<ffffffff81087da0>] ? autoremove_wake_function+0x0/0x40
[    2.910028]  [<ffffffff8136b900>] ? xenwatch_thread+0x0/0x170
[    2.910028]  [<ffffffff81087676>] kthread+0x96/0xa0
[    2.910028]  [<ffffffff8100cee4>] kernel_thread_helper+0x4/0x10
[    2.910028]  [<ffffffff810875e0>] ? kthread+0x0/0xa0
[    2.910028]  [<ffffffff8100cee0>] ? kernel_thread_helper+0x0/0x10
[    2.910028] Code: 8b 45 b0 74 15 48 8b 7d c8 89 45 b0 e8 93 e3 ff ff 4c 8b 6d c8 8b 45 b0 eb 90 4c 8b 6d c8 eb 8a 48 83 7f 30 00 0f 85 be fe ff ff <0f> 0b be b7 00 00 00 48 c7 c7 58 79 7d 81 e8 b6 fd e8 ff e9 dc
[    2.910028] RIP  [<ffffffff811d64b7>] internal_create_group+0x187/0x1a0
[    2.910028]  RSP <ffff88001f9b3ce0>
[    2.928247] ---[ end trace d4f9aa3628762312 ]---
[    3.836521] eth0: link up, 100Mbps, full-duplex, lpa 0x05E1
[    4.142405] parport_pc 00:0a: reported by Plug and Play ACPI