On Fri, Jul 22, 2022, Borislav Petkov wrote:

On Thu, Jun 23, 2022 at 10:43:40PM +0000, Kalra, Ashish wrote:

quoted

Yes, that's a nice way to hide it from the rest of the kernel which
does not require access to this structure anyway, in essence, it
becomes a private structure.

So this whole discussion whether there should be a model check or not
in case a new RMP format gets added in the future is moot - when a new
model format comes along, *then* the distinction should be done and
added in code - not earlier.

I disagree.  Running an old kernel on new hardware with a different RMP layout
should refuse to use SNP, not read/write garbage and likely corrupt the RMP and/or
host memory.

And IMO, hiding the non-architectural RMP format in SNP-specific code so that we
don't have to churn a bunch of call sites that don't _need_ access to the raw RMP
format is a good idea regardless of whether we want to be optimistic or pessimistic
about future formats.

This is nothing else but normal CPU enablement work - it should be done
when it is really needed.

Because the opposite can happen: you can add a model check which
excludes future model X, future model X comes along but does *not*
change the RMP format and then you're going to have to relax that model
check again to fix SNP on the new model X.

So pls add the model checks only when really needed.

Thx.

-- 
Regards/Gruss,
    Boris.

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