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

Sathyanarayanan Kuppuswamy
2022-08-29T20:34:28Z

On 8/29/22 1:28 PM, Dave Hansen wrote:
> 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.

Ok. I will add it in next version.

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer