On Saturday 17 March 2007 03:32:53 Len Brown wrote:
> On Friday 16 March 2007 19:44, Thomas Gleixner wrote:
> > Maxim,
> >
> > On Fri, 2007-03-16 at 12:30 +0200, Maxim Levitsky wrote:
> > > 3) Sometimes I get this (once in three boots or so)
> > >
> > > [ 36.217405] ENABLING IO-APIC IRQs
> > > [ 36.217587] ..TIMER: vector=0x31 apic1=0 pin1=2 apic2=-1 pin2=-1
> > > [ 36.433917] APIC timer disabled due to verification failure.
> > >
> > > And NO_HZ is disabled due to that (I get 1000/s timer's interrupts)
> > > I haven't investigated that yet.
> > > It looks like another new test that my hardware fails to perform...
> >
> > Yes, this is probably caused by SMM code trying to emulate a PS/2
> > keyboard from a (maybe connected or not) USB keyboard. Unfortunately we
> > have no way to disable this BIOS misfeature in the early boot process.
> > Arjan, Len ?????
>
> Nope. By definition, SMM is invisible to the OS -- we don't even
> get a bit that said it occurred (though we'd like one -- it would
> be really helpful to diagnose issues like this one)
>
> So go into BIOS SETUP and see if there is a USB Legacy Emulation
> feature that you can disable. Sometimes there is not, but disabling
> onboard USB altogether may help at least prove the issue is in that area.
>
> > I built in this test to rule out bogus LAPIC timer calibration values
> > which are sometimes off by factor 2-10.
> >
> > But I also built in a calibration against the PM-Timer, which turned out
> > to be quite reliable and I think the additional verification step is
> > only necessary for sytems without PM-Timer.
> >
> > That was a bit over cautious from my side. I send a patch to avoid this
> > when PM-Timer is available in a separate mail.
>
> PM-Timer was invented to work-around the issue that the TSC became unreliable
> in the face of power management on laptops. In particular, to be able
> to time duration of OS idle where TSC stopped.
>
> While it is not fine grain, and it is not low-latency, is should
> be very reliable. My understanding is that it is implemented as
> a simple divider right off the system 14MHz clock -- the signal
> which most motherboard clocks are PLL multiplied up from --
> including the 100MHz front-side bus which drives the LAPIC timer.
>
> But that said, I don't understand why calibrating the LAPIC timer
> using the PM-timer is going to be more reliable -- exactly how
> and why did the previous calibration scheme fail?
> Maybe I could follow the new logic in apic.c if I saw the "apic=debug"
> output for this box.
>
> cheers,
> -Len
>
>
>
Hi,
Yes, usb emulation is enabled, but I need it. I will test without usb
emulation, but since it shows only sometimes,
I don't know yet whenever usb legacy affects it.
Regards,
Maxim Levitsky
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