Greetings,

0day kernel testing robot got the below dmesg and the first bad commit is

commit 3dc4f7cfb7441e5e0fed3a02fc81cdaabd28300a
Author:     Marcelo Tosatti <mtosatti@redhat.com>
AuthorDate: Tue Nov 27 23:28:56 2012 -0200
Commit:     Marcelo Tosatti <mtosatti@redhat.com>
CommitDate: Tue Nov 27 23:29:10 2012 -0200

    x86: kvm guest: pvclock vsyscall support
    
    Hook into generic pvclock vsyscall code, with the aim to
    allow userspace to have visibility into pvclock data.
    
    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

+--------------------------------------------------------------+------------+------------+------------+
|                                                              | 71056ae22d | 3dc4f7cfb7 | d778df51c0 |
+--------------------------------------------------------------+------------+------------+------------+
| boot_successes                                               | 141        | 0          | 0          |
| boot_failures                                                | 0          | 47         | 11         |
| WARNING:at_arch/x86/kernel/pvclock.c:pvclock_init_vsyscall() | 0          | 47         | 11         |
| backtrace:pvclock_init_vsyscall                              | 0          | 47         | 11         |
| backtrace:warn_slowpath_null                                 | 0          | 47         | 11         |
| backtrace:kvm_setup_vsyscall_timeinfo                        | 0          | 47         | 11         |
| backtrace:kvm_guest_init                                     | 0          | 47         | 11         |
| Kernel_panic-not_syncing:Attempted_to_kill_init_exitcode=    | 0          | 0          | 7          |
| BUG:kernel_boot_hang                                         | 0          | 0          | 4          |
+--------------------------------------------------------------+------------+------------+------------+

[    0.000000] mapped IOAPIC to ffffffffff5f9000 (fec00000)
[    0.000000] nr_irqs_gsi: 40
[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: at arch/x86/kernel/pvclock.c:182 pvclock_init_vsyscall+0x41/0x8e()
[    0.000000] Hardware name: Standard PC (i440FX + PIIX, 1996)
[    0.000000] Modules linked in:
[    0.000000] Pid: 0, comm: swapper Not tainted 3.7.0-rc3-00112-g3dc4f7c #1
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff8104f750>] warn_slowpath_common+0x70/0xa0
[    0.000000]  [<ffffffff8104f83a>] warn_slowpath_null+0x1a/0x20
[    0.000000]  [<ffffffff8219a6af>] pvclock_init_vsyscall+0x41/0x8e
[    0.000000]  [<ffffffff8219a623>] kvm_setup_vsyscall_timeinfo+0x48/0x78
[    0.000000]  [<ffffffff8219a397>] kvm_guest_init+0x98/0xe1
[    0.000000]  [<ffffffff82190eb8>] setup_arch+0xa9b/0xb10
[    0.000000]  [<ffffffff818eeae8>] ? printk+0x4f/0x57
[    0.000000]  [<ffffffff8218e856>] start_kernel+0x93/0x388
[    0.000000]  [<ffffffff8218e120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff8218e2b4>] x86_64_start_reservations+0xb0/0xb3
[    0.000000]  [<ffffffff8218e3b9>] x86_64_start_kernel+0x102/0x10f
[    0.000000] ---[ end trace c9f7d63dd24af7e7 ]---
[    0.000000] KVM setup async PF for cpu 0

git bisect start v3.8 v3.7 --
git bisect  bad 8d91a42e54eebc43f4d8f6064751ccba73528275  # 21:30      0-      5  Merge tag 'omap-late-cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
git bisect  bad 770b6cb4d21fb3e3df2a7a51e186a3c14db1ec30  # 21:35      0-      1  ARM: OMAP: Fix drivers to depend on omap for internal devices
git bisect good 9977d9b379cb77e0f67bd6f4563618106e58e11d  # 21:40     30+      0  Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal
git bisect  bad e777d192ffb9f2929d547a2f8a5f65b7db7a9552  # 21:44      4-     26  Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
git bisect good 8b0cab14951fbf8126795ab301835a8f8126a988  # 22:00     30+      0  Merge tag 'regulator-3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator
git bisect good c7708fac5a878d6e0f2de0aa19f9749cff4f707f  # 22:11     30+      0  Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
git bisect  bad e05a1c6397a73d09389e033b6b2c25c954d2177c  # 22:17      0-      1  Merge tag 'ktest-v3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-ktest
git bisect good 896ea17d3da5f44b2625c9cda9874d7dfe447393  # 22:36     30+      0  Merge tag 'stable/for-linus-3.8-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen
git bisect  bad 66cdd0ceaf65a18996f561b770eedde1d123b019  # 22:41      3-      3  Merge tag 'kvm-3.8-1' of git://git.kernel.org/pub/scm/virt/kvm/kvm
git bisect good 8455d79e2163997e479931b8d5b7e60a92cd2b86  # 23:04     30+      0  KVM: PPC: Book3S HV: Run virtual core whenever any vcpus in it can run
git bisect  bad 78c634402a1825f1f5bef13077f0985f3b8a3212  # 23:11      3-     23  kvm: deliver msi interrupts from irq handler
git bisect good 189e11731aa858597095fbe1e6d243bad26bd96b  # 23:19     30+      0  x86: pvclock: add note about rdtsc barriers
git bisect  bad b48aa97e38206a84bf8485e7c553412274708ce5  # 23:42     22-      8  KVM: x86: require matched TSC offsets for master clock
git bisect  bad 886b470cb14733a0286e365c77f1844c240c33a4  # 00:28      2-      5  KVM: x86: pass host_tsc to read_l1_tsc
git bisect good 71056ae22d43f58d7e0f793af18ace2eaf5b74eb  # 01:09     47+      0  x86: pvclock: generic pvclock vsyscall initialization
git bisect  bad 51c19b4f5927f5a646e93d69f73c7e89ea14e737  # 02:16      0-      1  x86: vdso: pvclock gettime support
git bisect  bad 3dc4f7cfb7441e5e0fed3a02fc81cdaabd28300a  # 02:45      0-     24  x86: kvm guest: pvclock vsyscall support
# first bad commit: [3dc4f7cfb7441e5e0fed3a02fc81cdaabd28300a] x86: kvm guest: pvclock vsyscall support
git bisect good 71056ae22d43f58d7e0f793af18ace2eaf5b74eb  # 04:11    141+      0  x86: pvclock: generic pvclock vsyscall initialization


This script may reproduce the error.

----------------------------------------------------------------------------
#!/bin/bash

kernel=$1
initrd=quantal-core-x86_64.cgz

wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd

kvm=(
	qemu-system-x86_64
	-cpu kvm64
	-enable-kvm
	-kernel $kernel
	-initrd $initrd
	-m 320
	-smp 2
	-net nic,vlan=1,model=e1000
	-net user,vlan=1
	-boot order=nc
	-no-reboot
	-watchdog i6300esb
	-rtc base=localtime
	-serial stdio
	-display none
	-monitor null 
)

append=(
	hung_task_panic=1
	earlyprintk=ttyS0,115200
	debug
	apic=debug
	sysrq_always_enabled
	rcupdate.rcu_cpu_stall_timeout=100
	panic=-1
	softlockup_panic=1
	nmi_watchdog=panic
	oops=panic
	load_ramdisk=2
	prompt_ramdisk=0
	console=ttyS0,115200
	console=tty0
	vga=normal
	root=/dev/ram0
	rw
	drbd.minor_count=8
)

"${kvm[@]}" --append "${append[*]}"
----------------------------------------------------------------------------

Thanks,
Fengguang