Re: [kvm-devel] [BUG] Oops with KVM-27

From: Avi Kivity
Date: Tue Jun 12 2007 - 02:44:25 EST

Luca wrote:
> On 6/11/07, Avi Kivity <avi@xxxxxxxxxxxx> wrote:
>> Luca wrote:
>> >>
>> >> I've managed to reproduce this on kvm-21 (it takes many boots for
>> this
>> >> to happen, but it does eventually).
>> >
>> > Hum, any clue on the cause?
>> From what I've seen, it's the new Linux clocksource code.
> Actually I tried forcing the PIT (and any other combination of
> tsc,acpi_pm,jiffies) as the clocksource, without success.

Well, there's lots of APIC stuff going on when it hangs.

>> > Should I test older versions?
>> They're unlikely to be better. Instead, it would be best to see what
>> the guest is doing.
>> I suggest downloading the source rpm for the kernel, building it, and
>> sprinkling printk()s until we know exactly what source the guest is
>> executing at the time of the hang.
> Ok, will do. Meanwhile I discovered that the kernel on the boot cd
> (the one that hangs) is compiled for i586, while the one installed on
> disk is for i686 (this one works).


> i686 has this options enabled:
> but disabling tsc on the command line doesn't make any difference. Is
> it possible that KVM is choking on some instruction not used by the
> i686 kernel?

Unlikely, as then the hang would occur all the time instead of randomly.

Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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