KVM: x86/pmu: Reject userspace attempts to set reserved GLOBAL_STATUS bits

Reject userspace writes to MSR_CORE_PERF_GLOBAL_STATUS that attempt to set
reserved bits.  Allowing userspace to stuff reserved bits doesn't harm KVM
itself, but it's architecturally wrong and the guest can't clear the
unsupported bits, e.g. makes the guest's PMI handler very confused.

Signed-off-by: Like Xu <likexu@tencent.com>
[sean: rewrite changelog to avoid use of #GP, rebase on name change]
Link: https://lore.kernel.org/r/20230603011058.1038821-4-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>