KVM x86 fixes for 7.1-rcN
- Include the kernel's linux/mman.h in KVM selftests to ensure MADV_COLLAPSE
is defined, as older libc versions may not provide it.
- Include execinfo.h if and only if KVM selftests are building against glibc,
and provide a test_dump_stack() for non-glibc builds.
- Fudge around an RCU splat in the emegerncy reboot code that is technically
a legitimate flaw, but in practice is a non-issue and fixing the flaw, e.g.
by adding locking, would incur meaningful risk, i.e. do more harm than good.
- Rate-limit global clock updates once again (but without delayed work), as
KVM was subtly relying on the old rate-limiting for NPT correction to guard
against "update storms" when running without a master clock on systems with
overcommitted CPUs.
- Fix a brown paper bag goof where KVM checked if ERAPS is "dirty" instead of
marking it dirty when emulating INVPCID.
- Flush the TLB when transitioning from xAVIC => x2AVIC to ensure the CPU TLB
doesn't contain AVIC-tagged entries for the APIC base GPA.