libvirt platform quality of service

To run real-time workloads on commodity hardware effectively requires that the
guest and host be tuned for deterministic low latency and high throughput.
Typically this is done using the existing enhanced platform awareness (EPA)
features such as hugepages, CPU pinning and emulator thread policies on a
real-time host kernel. If the host also runs non-realtime workloads or
unoptimized workloads, the determinism afforded by the careful tuning of
the guest can be undone due to noisy neighbor effects such as cache thrashing
or memory bandwidth exhaustion. This can be adddressed by static
allocation of cache and memory bandwidth limits leveraging platform
quality of service