x86/timer: Force PIT initialization when !X86_FEATURE_ARAT
KVM guests with commit c8c40767 ("x86/timer: Skip PIT initialization on modern chipsets") applied to guest kernel have been observed to have unusually higher CPU usage with symptoms of increase in vm exits for HLT and MSW_WRITE (MSR_IA32_TSCDEADLINE). This is caused by older QEMUs lacking support for X86_FEATURE_ARAT. lapic clock retains CLOCK_EVT_FEAT_C3STOP and nohz stays inactive. There's no usable broadcast device either. Do the PIT initialization if guest CPU lacks X86_FEATURE_ARAT. On real hardware it shouldn't matter as ARAT and DEADLINE come together. Fixes: c8c40767 ("x86/timer: Skip PIT initialization on modern chipsets") Signed-off-by:Jan Stancek <jstancek@redhat.com> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de>
parent
e16c2983
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