Re: [Qemu-devel] [BUG] Guest kernel divide error in kvm_unlock_kick

[Paolo Bonzini]

Il 11/09/2014 19:03, Chris Webb ha scritto:
> Paolo Bonzini <address@hidden> wrote:
> 
>> This is a hypercall that should have kicked VCPU 3 (see rcx).
>>
>> Can you please apply this patch and gather a trace of the host
>> (using "trace-cmd -e kvm qemu-kvm <arguments>")?
> 
> Sure, no problem. I've built the trace-cmd tool against udis86 (I hope) and
> have put the resulting trace.dat at
> 
>   http://cdw.me.uk/tmp/trace.dat
> 
> This is actually for a -smp 2 qemu (failing to kick VCPU 1?) as I was having
> trouble persuading the -smp 4 qemu to crash as reliably under tracing.
> (Something timing related?) Otherwise the qemu-system-x86 command line is
> exactly as before.

Do you by chance have CONFIG_DEBUG_RODATA set?  In that case, the fix is
simply not to set it.

Paolo

> The guest kernel crash message which corresponds to this trace was:
> 
> divide error: 0000 [#1] PREEMPT SMP 
> Modules linked in:
> CPU: 0 PID: 618 Comm: mkdir Not tainted 3.16.2-guest #2
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
> rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
> task: ffff88007c997080 ti: ffff88007c614000 task.ti: ffff88007c614000
> RIP: 0010:[<ffffffff81037fe2>]  [<ffffffff81037fe2>] kvm_unlock_kick+0x72/0x80
> RSP: 0018:ffff88007c617d40  EFLAGS: 00010046
> RAX: 0000000000000005 RBX: 0000000000000000 RCX: 0000000000000001
> RDX: 0000000000000001 RSI: ffff88007fd11c40 RDI: 0000000000000000
> RBP: ffff88007fd11c40 R08: ffffffff81b98940 R09: 0000000000000001
> R10: 0000000000000000 R11: 0000000000000007 R12: 00000000000000f6
> R13: 0000000000000001 R14: 0000000000000001 R15: 0000000000011c40
> FS:  00007f43eb1ed700(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 00007f43eace0a30 CR3: 0000000001a12000 CR4: 00000000000406f0
> Stack:
>  ffff88007c994380 ffff88007c9949aa 0000000000000046 ffffffff81689715
>  ffffffff810f3174 0000000000000001 ffffea0001f16320 ffffea0001f17860
>  0000000000000000 ffff88007c99e1e8 ffff88007c997080 0000000000000001
> Call Trace:
>  [<ffffffff81689715>] ? _raw_spin_unlock+0x45/0x70
>  [<ffffffff810f3174>] ? try_to_wake_up+0x2a4/0x330
>  [<ffffffff81101e2c>] ? __wake_up_common+0x4c/0x80
>  [<ffffffff81102418>] ? __wake_up_sync_key+0x38/0x60
>  [<ffffffff810d873a>] ? do_notify_parent+0x19a/0x280
>  [<ffffffff810f4d56>] ? sched_move_task+0xb6/0x190
>  [<ffffffff810cb4fc>] ? do_exit+0xa1c/0xab0
>  [<ffffffff810cc344>] ? do_group_exit+0x34/0xb0
>  [<ffffffff810cc3cb>] ? SyS_exit_group+0xb/0x10
>  [<ffffffff8168a16d>] ? system_call_fastpath+0x1a/0x1f
> Code: c0 ca a7 81 48 8d 04 0b 48 8b 30 48 39 ee 75 c9 0f b6 40 08 44 38 e0 75 
> c0 48 c7 c0 22 b0 00 00 31 db 0f b7 0c 08 b8 05 00 00 00 <0f> 01 c1 0f 1f 00 
> 5b 5d 41 5c c3 0f 1f 00 48 c7 c0 10 cf 00 00 
> RIP  [<ffffffff81037fe2>] kvm_unlock_kick+0x72/0x80
>  RSP <ffff88007c617d40>
> ---[ end trace bf5a4445f9decdbb ]---
> Fixing recursive fault but reboot is needed!
> BUG: scheduling while atomic: mkdir/618/0x00000006
> Modules linked in:
> CPU: 0 PID: 618 Comm: mkdir Tainted: G      D       3.16.2-guest #2
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
> rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
>  0000000000000000 00000000c022d302 ffffffff81684029 0000000000000000
>  ffffffff810ee956 ffffffff81686266 0000000000011c40 ffff88007c617fd8
>  0000000000011c40 ffff88007c997080 0000000000000006 0000000000000046
> Call Trace:
>  [<ffffffff81684029>] ? dump_stack+0x49/0x6a
>  [<ffffffff810ee956>] ? __schedule_bug+0x46/0x60
>  [<ffffffff81686266>] ? __schedule+0x5a6/0x7c0
>  [<ffffffff816828cd>] ? printk+0x59/0x75
>  [<ffffffff810cb33b>] ? do_exit+0x85b/0xab0
>  [<ffffffff816828cd>] ? printk+0x59/0x75
>  [<ffffffff8100614a>] ? oops_end+0x7a/0x100
>  [<ffffffff810033e5>] ? do_error_trap+0x85/0x110
>  [<ffffffff81037fe2>] ? kvm_unlock_kick+0x72/0x80
>  [<ffffffff8114a358>] ? __alloc_pages_nodemask+0x108/0xa60
>  [<ffffffff8168b57e>] ? divide_error+0x1e/0x30
>  [<ffffffff81037fe2>] ? kvm_unlock_kick+0x72/0x80
>  [<ffffffff81689715>] ? _raw_spin_unlock+0x45/0x70
>  [<ffffffff810f3174>] ? try_to_wake_up+0x2a4/0x330
>  [<ffffffff81101e2c>] ? __wake_up_common+0x4c/0x80
>  [<ffffffff81102418>] ? __wake_up_sync_key+0x38/0x60
>  [<ffffffff810d873a>] ? do_notify_parent+0x19a/0x280
>  [<ffffffff810f4d56>] ? sched_move_task+0xb6/0x190
>  [<ffffffff810cb4fc>] ? do_exit+0xa1c/0xab0
>  [<ffffffff810cc344>] ? do_group_exit+0x34/0xb0
>  [<ffffffff810cc3cb>] ? SyS_exit_group+0xb/0x10
>  [<ffffffff8168a16d>] ? system_call_fastpath+0x1a/0x1f
> 
> Best wishes,
> 
> Chris.
>