Re: VM not booting anymore after Ubuntu upgrade

[Avi Kivity <avi@redhat.com>]

  On 08/04/2010 10:38 AM, André Weidemann wrote:
>
>> Please enable ftrace:
>>
>> # mount -t debugfs debugfs /sys/kernel/debug
>> # cd /sys/kernel/debug/tracing
>> # echo 100000 > buffer_size_kb
>> # echo kvm > set_event
>> # echo 1 > tracing on
>>
>> run the guest and kill qemu immediately when you get to the blank screen
>> (use SDL so you can see it immediately). Then post
>> /sys/kernel/debug/trace somewhere.
>
> I ran the trace and put the ouptut here:
> http://ilpss8.dyndns.org/~andrew/qemu-kvm.trace.gz
>


<...>-26008 [001] 5175193.046430: kvm_exit: reason exception rip 0xfc842
<...>-26008 [001] 5175193.046430: kvm_page_fault: address fc842 error_code 9
<...>-26008 [001] 5175193.046432: kvm_entry: vcpu 0
<...>-26008 [001] 5175193.046434: kvm_exit: reason cr_access rip 0xfc796
<...>-26008 [001] 5175193.046435: kvm_cr: cr_write 0 = 0x10
<...>-26008 [001] 5175193.046442: kvm_entry: vcpu 0
<...>-26008 [001] 5175193.046444: kvm_exit: reason exception rip 0xfc799
<...>-26008 [001] 5175193.046447: kvm_entry: vcpu 0
<...>-26008 [001] 5175193.046449: kvm_exit: reason exception rip 0xfc799
<...>-26008 [001] 5175193.046449: kvm_page_fault: address feffd066 
error_code 9
<...>-26008 [001] 5175193.046453: kvm_inj_virq: irq 13

#GP at fc799.

    fc78f:       0f 20 c0                mov    %cr0,%eax
    fc792:       66 83 e0 fe             and    $0xfffffffe,%eax
    fc796:       0f 22 c0                mov    %eax,%cr0
    fc799:       ea 9e c7 00 f0          ljmp   $0xf000,$0xc79e

I think we're in big real mode and your kernel has trouble emulating the 
ljmp.  Can you try latest seabios[1]?  Commit 0f788893a8bba has a 
workaround.


[1] git://git.linuxtogo.org/home/kevin/seabios.git

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.