xen-kernel -- some pmu and profiling hypercalls log without rate limiting

The Xen Project reports:

HYPERCALL_xenoprof_op and HYPERVISOR_xenpmu_op log some errors and
attempts at invalid operations. These log messages are not
rate-limited, even though they can be triggered by guests.
A malicious guest could cause repeated logging to the hypervisor
console, leading to a Denial of Service attack.