Re: [PATCH v3 0/4] x86/time: calibration rendezvous adjustments

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.02.2021 13:53, Jan Beulich wrote:
> The middle two patches are meant to address a regression reported on
> the list under "Problems with APIC on versions 4.9 and later (4.8
> works)". In the course of analyzing output from a debugging patch I
> ran into another anomaly again, which I thought I should finally try
> to address. Hence patch 1. Patch 4 is new in v3 and RFC for now.

Of course this is the kind of change I'd prefer doing early in a
release cycle. I don't think there are severe risks from patch 1, but
I'm not going to claim patches 2 and 3 are risk free. They fix booting
Xen on a system left in rather awkward state by the firmware. And
they shouldn't affect well behaved modern systems at all (due to
those using a different rendezvous function). While we've been having
this issue for years, I also consider this set a backporting
candidate. Hence I can see reasons pro and con inclusion in 4.15.

Jan

> 1: change initiation of the calibration timer
> 2: adjust time recording time_calibration_tsc_rendezvous()
> 3: don't move TSC backwards in time_calibration_tsc_rendezvous()
> 4: re-arrange struct calibration_rendezvous
> 
> Jan
>