Re: nmi is broken?

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-04-24 11:17, OGAWA Hirofumi wrote:
> Avi Kivity <avi@redhat.com> writes:
> 
>>> With some debug, the cause seems to be in pit_do_work(). With the
>>> following patch, NMI watchdog seems to be working correctly (if irq
>>> disabled for long time, NMI watchdog can detect it).
>>>
>>> Is the following patch right?
>>
>> This would cause IRQs to be delivered even if the PIT is masked, no?
> 
> In here, mask means pit_mask_notifer()? If masked, ->pending doesn't
> prevent to fire it? I'm not sure.
> 
>> Are you in fact using the PIT?  Linux prefers the HPET, and in my 
>> experience the -no-hpet option makes NMIs work.
> 
> Yes, this is old kernel (2.6.9), and is not using HPET
> (CONFIG_HPET_TIMER=n), using IO-APIC as NMI source (PMU seems to be
> unsupported on kvm for now).
> 
> Unfortunately, -no-hpet didn't change situation. irq_stat.apic_timer_irqs
> and nmi_count() are same while irq is disabled.

Maybe it's a regression of latest NMI injection patches.

This worked before? Can you check if commits
c2dd554dc61173ecb6b3741b680d2ae4c245d2ba and
f86368493ec038218e8663cc1b6e5393cd8e008a have any impact on your problem?

Jan


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