New: "user requested TSC rate below hardware speed" warning

https://bugzilla.kernel.org/show_bug.cgi?id=205151

Bug ID: 205151
Summary: "user requested TSC rate below hardware speed" warning
Product: Virtualization
Version: unspecified
Kernel Version: 5.3
Hardware: x86-64
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: kvm
Assignee: [email protected]
Reporter: [email protected]
Regression: Yes

5.3 seems to have broken TSC, at least for qemu/kvm VMs. After 5.3 upgrade starting a VM gets me "user requested TSC rate below hardware speed" warnings (1 per assigned core).

I'm not quite sure when kind of data I could provide, however after a short while (several minutes) drift becomes quite noticable (severe audio/video desync).

Relevant(?) dmesg entries from 5.3:

[Sun Oct  6 16:59:21 2019] tsc: Detected 4000.000 MHz processor
[Sun Oct  6 16:59:21 2019] tsc: Detected 3999.984 MHz TSC
[Sun Oct  6 16:59:22 2019] tsc: Refined TSC clocksource calibration: 4008.064
MHz
[Sun Oct  6 17:00:48 2019] user requested TSC rate below hardware speed
[Sun Oct  6 17:00:48 2019] user requested TSC rate below hardware speed

And 5.2:

[Thu Oct  3 21:56:01 2019] tsc: Detected 4000.000 MHz processor
[Thu Oct  3 21:56:01 2019] tsc: Detected 4008.000 MHz TSC

(no refined calibration here)

My CPU is Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz (family: 0x6, model: 0x5e,
stepping: 0x3).

Revering commit 604dc9170f2435d27da5039a3efd757dceadc684 fixes the problem.

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