[B][PATCH 0/1] LP#1822821 TSC clocksource not available in nested guests

Heitor R. Alves de Siqueira halves at canonical.com
Tue Apr 2 17:49:32 UTC 2019

BugLink: https://bugs.launchpad.net/bugs/1822821

 * TSC clocksource not available in nested guests

[Test Case]
 * Spin up a nested Xenial/Bionic guest and check for 'tsc' at

[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

 * 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)

[Other Info]
 * Xenial needs 2 patches, Bionic needs 1 patch
 * Cosmic onwards (kernels 4.18+) are already fixed

Peng Hao (1):
  kvmclock: fix TSC calibration for nested guests

 arch/x86/kernel/kvmclock.c | 1 +
 1 file changed, 1 insertion(+)


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