CVE-2021-47112

In the Linux kernel, the following vulnerability has been resolved:
x86/kvm: Teardown PV features on boot CPU as well Various PV features
(Async PF, PV EOI, steal time) work through memory shared with hypervisor
and when we restore from hibernation we must properly teardown all these
features to make sure hypervisor doesn’t write to stale locations after we
jump to the previously hibernated kernel (which can try to place anything
there). For secondary CPUs the job is already done by
kvm_cpu_down_prepare(), register syscore ops to do the same for boot CPU.