Re: [PATCH v8 01/40] x86/compressed/64: detect/setup SEV/SME features earlier in boot

Michael Roth
2021-12-15T21:23:22Z

On Wed, Dec 15, 2021 at 09:38:55PM +0100, Borislav Petkov wrote:
> On Wed, Dec 15, 2021 at 02:17:34PM -0600, Michael Roth wrote:
> > and if fields are added in the future:
> >
> > sev_parse_cpuid(AMD_SEV_BIT, &me_bit_pos, &vte_enabled, &new_feature_enabled, etc..)
>
> And that will end up being a vararg function because of who knows what
> other feature bits will have to get passed in? You have even added the
> ellipsis in there.

Well, not varargs, just sort of anticipating how the function prototype
might change over time as it's modified to parse for new features.

>
> Nope. Definitely not.
>
> > or if that eventually becomes unwieldly
>
> The above example is already unwieldy.
>
> > it could later be changed to return a feature mask.
>
> Yes, that. Clean and simple.
>
> But it is hard to discuss anything without patches so we can continue
> the topic with concrete patches. But this unification is not
> super-pressing so it can go ontop of the SNP pile.

Yah, it's all theoretical at this point. Didn't mean to derail things
though. I mainly brought it up to suggest that Venu's original approach of
returning the encryption bit via a pointer argument might make it easier to
expand it for other purposes in the future, and that naming it for that
future purpose might encourage future developers to focus their efforts
there instead of potentially re-introducing duplicate code.

But either way it's simple enough to rework things when we actually
cross that bridge. So totally fine with saving all of this as a future
follow-up, or picking up either of Venu's patches for now if you'd still
prefer.

Thanks,

Mike

>
> Thx.
>
> --
> Regards/Gruss,
> Boris.
>
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