Re: [PATCHv7.1 02/30] x86/tdx: Provide common base for SEAMCALL and TDCALL C wrappers
From: Kai Huang
Date: Mon Apr 04 2022 - 21:58:04 EST
On Mon, 2022-04-04 at 17:01 -0700, Dave Hansen wrote:
> 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.
OK. How about below:
* VMfailInvalid happens before any actual internal logic of the
* P-SEAMLDR and the TDX module is reached. Use a unique value which
* will never conflict with any actual error code returned by both the
* P-SEAMLDR and the TDX module to represent this case.
* Both error code definitions of the P-SEAMLDR and the TDX module have
* some reserved bits (bits 61:48 for the TDX module and bits 62:32 for
* the P-SEAMLDR) which will never be set to 1. Choose -1ULL as it
* never be returned as error code by both of them.
#define TDX_SEAMCALL_VMFAILINVALID GENMASK_ULL(63, 0)