KVM: TDX: Set bits 31:16 to 0 and use UNDEFINED when synthesizing exit reason

Set bits 31:16 to 0 instead of all-1s when synthesizing an exit reason,
e.g. if the TDX Module never attempted VM-Enter, or when stuffing the exit
reason due to an unexpected "real" EPT Misconfig.  Opportunistically use
VMX's KVM-defined EXIT_REASON_UNDEFINED (0xdead) instead of -1u.

KVM is going to support Bus Lock VM exit for TDX, after which bit 26 of
the Exit Reason becomes meaningful and indicates that a bus lock happened.
The existing synthesized Exit Reason, -1u, will cause a false positive in
that case.  Change the synthesized Exit Reason from -1u to U16_MAX, so that
bits 31:16 are set to 0.  This also avoids the potential issues when other
bits in 31:16 become valid in the future.

As a bonus, the check for synthesized Exit Reason in tdx_failed_vmentry()
becomes unnecessary.  Just drop it.

Cc: stable@vger.kernel.org
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://patch.msgid.link/20260819094903.3060020-4-xiaoyao.li@intel.com
[sean: use EXIT_REASON_UNDEFINED instead of another magic value]
Signed-off-by: Sean Christopherson <seanjc@google.com>

0 files changed, 0 insertions, 0 deletions