KVM: x86: use raw clock values consistently
Commit 53fafdbb ("KVM: x86: switch KVMCLOCK base to monotonic raw clock") changed kvmclock to use tkr_raw instead of tkr_mono. However, the default kvmclock_offset for the VM was still based on the monotonic clock and, if the raw clock drifted enough from the monotonic clock, this could cause a negative system_time to be written to the guest's struct pvclock. RHEL5 does not like it and (if it boots fast enough to observe a negative time value) it hangs. There is another thing to be careful about: getboottime64 returns the host boot time with tkr_mono frequency, and subtracting the tkr_raw-based kvmclock value will cause the wallclock to be off if tkr_raw drifts from tkr_mono. To avoid this, compute the wallclock delta from the current time instead of being clever and using getboottime64. Fixes: 53fafdbb ("KVM: x86: switch KVMCLOCK base to monotonic raw clock") Cc: stable@vger.kernel.org Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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