Dear Xen developers,
Recently I read a paper about possible theft of service attacks in Xen
hypervisor.
https://arxiv.org/pdf/1103.0759.pdf
Due to the 10 ms intervals between sampling points, a malicious VM is
able to run less than a interval and sleep to avoid being accounted.
According to the info page of RTDS, it seems that after V4.7, a RTDS
based scheduler achieves a granularity of microsecond. However, is it
able that a VM runs for less than a microsecond and relinquish the
host actively so as to keep its budget?
A similar problem occurs in earlier Linux kernel, and it is fixed in
today's Linux on x86 machines by utilizing a clock source TSC with a
granularity of nanoseconds. I'd like to know if there is any reason
that the Xen hypervisor does not choose a nanosecond scheduler?
Thanks a lot.
Best,
Wenqiu
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