KVM: nVMX: WARN once and fail VM-Enter if eVMCS sees VMFUNC[63:32] != 0

KVM: nVMX: WARN once and fail VM-Enter if eVMCS sees VMFUNC[63:32] != 0

WARN and reject nested VM-Enter if KVM is using eVMCS and manages to
allow a non-zero value in the upper 32 bits of VM-function controls.  The
eVMCS code assumes all inputs are 32-bit values and subtly drops the
upper bits.  WARN instead of adding proper "support", it's unlikely the
upper bits will be defined/used in the next decade.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830133737.1539624-15-vkuznets@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>