Re: [PATCHv7.1 02/30] x86/tdx: Provide common base for SEAMCALL and TDCALL C wrappers

[Dave Hansen <dave.hansen@intel.com>]

On 4/4/22 16:35, Kai Huang wrote:
> Both error code formats defined by P-SEAMLDR and TDX module has some reserved
> bits which will never be set to 1.  I think we can just add a simple comment
> explaining that and choose a value which has 1 set for those reserved bits (even
> doesn't have to be -1). For example:
> 
> 	/*
> 	 * Use -1ULL which will never conflict with any actual error code
> 	 * returned by both the P-SEAMLDR and the TDX module to represent
> 	 * VMfailInvalid.  Both error code definitions defined by the
> 	 * P-SEAMLDR and the TDX module have some reserved bits which will
> 	 * never be set to 1.
> 	 */
> 	#define TDX_SEAMCALL_VMFAILINVALID	GENMASK_ULL(63, 0)

The vague "some reserved bits" magic works for exactly *one* error code.
 If you ever want to make it two, then you subject some some poor future
dope to a trip to TDX documentation purgatory.

All I'm asking is that this code stand on its own.  Just declare what
the *ACTUAL* reserved bits are.  Not some vague reference to "some
bits".  There are *REAL* documented bits.  Use them, please.