Re: [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe

[Martin Wilck]

Hi Cyrill,

> btw, Martin, don't get me wrong please - i'm not just complaining :)
> The changes you propose is important enough _but_ it could introduce
> regression. Look, with situation of miscalibrated apic timer kernel
> was working before but with the patch it could stop to work. So if
> user has a such screwed motherboard he could be shocked if it stop
> booting with message about SMI happened. we defenitely have to provide
> some workaround for this. And your max iteration counter solution
> would be fine I think.

Let's see what other people think about this. I am fine with both 
solutions. Currently only the first one has been tested though (testing 
these patches thoroughly needs long-time reboot tests).

One more remark: There are similar calibration routines around in the 
kernel which suffer from similar problems as calibrate_APIC_clock(). 
AFAIK, only calibrate_delay() was made SMI-safe by Venkatesh Pallipadi 
years ago.

Martin

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Martin Wilck
PRIMERGY System Software Engineer
FSC IP ESP DEV 6

Fujitsu Siemens Computers GmbH
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Germany

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