[Impact]
* TSC clocksource not available in nested guests
[Test Case]
* Spin up a nested Xenial/Bionic guest and check for 'tsc' at
/sys/devices/system/clocksource/clocksource0/available_clocksource
[Regression Potential]
* The regression potential is low. Upstream code still maintains this
behaviour of skipping calibration on guests, and tsc code verifies if
the frequency is known before registering the clocksource
* Patches were verified against the above test case, and also tested
with stress-ng in both nested and non-nested guest scenarios
[Fix]
* By applying the upstream commits, we skip refined calibration and
register TSC as a clocksource directly if its frequency is known (via
MSR or CPUID)
[Impact]
* TSC clocksource not available in nested guests
[Test Case] devices/ system/ clocksource/ clocksource0/ available_ clocksource
* Spin up a nested Xenial/Bionic guest and check for 'tsc' at
/sys/
[Regression Potential]
* The regression potential is low. Upstream code still maintains this
behaviour of skipping calibration on guests, and tsc code verifies if
the frequency is known before registering the clocksource
* Patches were verified against the above test case, and also tested
with stress-ng in both nested and non-nested guest scenarios
[Fix]
* By applying the upstream commits, we skip refined calibration and
register TSC as a clocksource directly if its frequency is known (via
MSR or CPUID)