Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v3 2/2] x86/tsc: skip tsc watchdog checking for qualified platforms | Date | Wed, 01 Dec 2021 00:19:43 +0100 |
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On Tue, Nov 30 2021 at 14:48, Paul E. McKenney wrote: > On Tue, Nov 30, 2021 at 10:55:45PM +0100, Thomas Gleixner wrote: >> > OK, HPET or nothing, then. >> >> Older machines also have pm_timer. But those beasts seem to have lost >> that too. > > I suppose that one way of avoiding clock-skew messages is to have only > one clock.
Indeed. It's a complete mystery why it takes ages to implement reliable clocks in hardware.
>> >> We really need to remove the watchdog requirement for modern hardware. >> >> Let me stare at those patches and get them merged. >> > >> > You are more trusting of modern hardware than I am, but for all I know, >> > maybe rightfully so. ;-) >> >> Well, I rather put a bet on the hardware, which has become reasonable >> over the last decade, than on trying to solve a circular dependency >> problem with tons of heuristics which won't ever work correctly. > > Use of HPET to check the interval length would not be circular, right?
As long as the HPET works reliably :)
>> TSC_ADJUST is a reasonable safety net and since its invention the amount >> of BIOS wreckage has been massively reduced. Seems the nastigram in >> dmesg when detecting a change in TSC_ADJUST had an effect or maybe >> Microsoft enforces a tinkerfree TSC by now and we get the benefit. :) >> >> I still wish to have a knob to lock down TSC to read only, but that's >> probably for christmas 2030 or later. :) > > Indeed. How would BIOS writers hide their SMI handlers? :-/
TSC_ADJUST already ruined that party.
Thanks,
tglx
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