KVM: x86: fix maintaining of kvm_clock stability on guest CPU hotplug

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VCPU TSC synchronization is perfromed in kvm_write_tsc() when the TSC
value being set is within 1 second from the expected, as obtained by
extrapolating of the TSC in already synchronized VCPUs.

This is naturally achieved on all VCPUs at VM start and resume;
however on VCPU hotplug it is not: the newly added VCPU is created
with TSC == 0 while others are well ahead.

To compensate for that, consider host-initiated kvm_write_tsc() with
TSC == 0 a special case requiring synchronization regardless of the
current TSC on other VCPUs.

Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

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Denis Plotnikov 2017-04-07 12:09:53 +03:00 • committed by Radim Krčmář

parent c5e8ec8e9b

commit bd8fab39cd

1 changed files with 19 additions and 10 deletions

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arch/x86/kvm/x86.c

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