Messages in this thread | | | Date | Fri, 25 Jul 2008 17:48:31 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe (take 2) |
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[Martin Wilck - Fri, Jul 25, 2008 at 03:38:47PM +0200] > I wrote: > >> I have to say that my simplified patch failed to do the calibration >> correctly on our test system (the original patch worked well). Please >> stay tuned, we are investigating this currently. > > Please forget that. It was observed on an old "enterprise" kernel with > which we are currently testing the backported patch with, and it was due > to the fact that the initial counter value on that kernel was divided by > APIC_DIVISOR (=16). The resulting initial counter value was too low in a > "SMI flood" case, the counter could overlap. APIC_DIVISOR is no longer > used in the current kernel. > > Martin > > --
Martin, if I understood you right - this means your patch is not needed? Actually on 64bit mode APIC_DIVISOR is a bit hidden in __setup_APIC_LVTT - you may see it as APIC_TDR_DIV_16 while setting up divisor register. I was proposing patch for that but it leaded to potetntial overflow (thanks Ingo for catching) so we leave it as is. Maybe I miss something?
- Cyrill -
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