Re: [PATCH 6.18.y] KVM: VMX: Formally define KVM's "0xdead" exit reason used for failed VM-Enter

[Sean Christopherson <seanjc@google.com>]

On Thu, Nov 05, 2026, Xiaoyao Li wrote:
> From: Sean Christopherson <seanjc@google.com>
> 
> [ Upstream commit d85f7dc8cf3c91a131946dae4c3aa8d9c97322d7 ]
> 
> 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>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---

In the future, please provide a quick explanation of the conflict resolution(s),
it helps me assess the safety/correctness of the backport, and provides a paper
trail to help with debug in case the backport introduces a bug.

For this, there was a superficial conflict due to lack of upstream commit
3c75e6a5da3c0 ("KVM: VMX: Move architectural "vmcs" and "vmcs_hdr" structures
to public vmx.h").

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