Referring to the following quote https://www.kernel.org/doc/Documentation/virtual/kvm/timekeeping.txt
4.8) Covert channels and leaks
In addition to the above problems, time information will inevitably leak to the guest about the host in anything but a perfect implementation of virtualized time. This may allow the guest to infer the presence of a hypervisor (as in a red-pill type detection), and it may allow information to leak between guest by using CPU utilization itself as a signalling channel. Preventing such problems would require completely isolated virtual time which may not track real time any longer. This may be useful in certain security or QA contexts, but in general isn't recommended for real-world deployment scenarios.
How to get a completely isolated virtual time with the virtualizer Xen?