Re: [PATCH v8 27/40] x86/boot: Add Confidential Computing type to setup_data

Dave Hansen
2021-12-13T15:08:13Z

On 12/13/21 6:49 AM, Brijesh Singh wrote:
>> I was more concerned that this structure could change sizes if it were
>> compiled on 32-bit versus 64-bit code.  For kernel ABIs, we try not to
>> do that.
>>
>> Is this somehow OK when talking to firmware?  Or can a 32-bit OS and
>> 64-bit firmware never interact?
>
> For SNP, both the firmware and OS need to be 64-bit. IIRC, both the
> Linux and OVMF do not enable the memory encryption for the 32-bit.

Could you please make the structure's size invariant? That's great if
there's no problem in today's implementation, but it's best no to leave
little land mines like this around. Let's say someone copies your code
as an example of something that interacts with a firmware table a few
years or months down the road.