KVM: VMX: Formally define KVM's "0xdead" exit reason used for failed VM-Enter

Add EXIT_REASON_UNDEFINED to track KVM's magic "0xdead" value that's used
to stuff the exit reason on a failed VM-Enter so that the magic can be
reused by TDX, and to make it more obvious that it's an arbitrary, KVM-
defined value (though the whole "dead" thing makes it pretty darn obvious).

Opportunistically add a compile-time assert to ensure the KVM-defined exit
reason never collides with a "real" exit reason.

No functional change intended.

Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Yan Zhao <yan.y.zhao@intel.com>
Cc: Binbin Wu <binbin.wu@linux.intel.com>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://patch.msgid.link/20260921235656.1107929-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

0 files changed, 0 insertions, 0 deletions