Re: [PATCH v11 1/3] x86/tdx: Add TDX Guest attestation interface driver

Dave Hansen
2022-08-29T20:28:13Z

On 8/29/22 13:09, Sathyanarayanan Kuppuswamy wrote:
> With the changed format, we avoided the holes, but it still adds 7 bytes of padding.
>
> Total size of struct is 32 bytes.
>
> struct tdx_report_req {
> __u64 reportdata; /* 0 8 */
> __u64 tdreport; /* 8 8 */
> __u32 rpd_len; /* 16 4 */
> __u32 tdr_len; /* 20 4 */
> __u8 subtype; /* 24 1 */
>
> /* size: 32, cachelines: 1, members: 5 */
> /* padding: 7 */
> /* last cacheline: 32 bytes */
> };

Might as well make some use of the padding and add:

u8 reserved[7];

That will ensure that the entire structure is explicitly sized *AND*
leave you room to add flags or other fun in the future without a new ABI.