Re: smp guest questions

[Marcelo Tosatti <mtosatti@redhat.com>]

On Wed, Jun 17, 2009 at 02:46:47PM +0400, Michael Tokarev wrote:
> Avi Kivity wrote:
>> On 06/17/2009 11:38 AM, Michael Tokarev wrote:
>>> After seeing words from Avi about that smp guests
>>> are ok now, I descided to try.  And immediately
>>> got a few questions.
>>>
>>> Running on a Phenom 9750 machine (PhenomI), AMD780G
>>> chipset.  Host is 2.6.29 x86-64, qemu-kvm 0.10.5,
>>> guests are linux with kvm paravirt bits enabled, also
>>> dynticks (on both host and guest).
>>>
>>>
>>> When booting a 2-CPU guest, I see in dmesg:
>>>
>>> PM-Timer running at invalid rate: 200% of normal - aborting.
>>>
>>> and indeed, in available_clocksource there's no pmtimer.
>>> Should I be concerned?  It does not look healthy.
>>>
>>
>> It's a bug, please post guest details (kernel version, bitness).
>
> The guest kernel is also 2.6.29[.5], but this time it's x86-32
> (compiled for P4).  kvm userspace is also 32bits (historical) --
> only host kernel is 64bit for now.  I'll try to do some more
> experiments later today on a test machine (this is a production
> box) -- "hopefully" that same issue will occur on another
> machine :)

kernel tries to correlate pm-timer with PIT:

http://lxr.linux.no/linux+v2.6.17/arch/i386/kernel/timers/timer_pm.c#L95

http://lxr.linux.no/linux+v2.6.17/include/asm-i386/mach-default/mach_timer.h#L39

Should be fixed before the Brazil world cup.