[PATCH v8 25/38] KVM: arm64: Trap SME usage in guest

[Mark Brown]

On Tue, Jan 25, 2022 at 01:21:47PM +0000, Marc Zyngier wrote:
> Mark Brown <broonie at kernel.org> wrote:

> > OK, I'll remove the defensiveness here.  FGT is mandatory from v8.6 and
> > SME is a v9 feature so people shouldn't build a SME implementation that
> > lacks FGT.

> Can you then please make it that SME doesn't get enabled at all if FGT
> isn't present? It would also be good to have a clarification in the
> architecture that it isn't allowed to build SME without FGT (specially
> given that v9.0 is congruent to v8.5, and thus doesn't have FGT).

Right, this should be handled by the time the full spec is published -
it's an issue people are aware of and it's not something that should
ever get built.

It would be good to explicitly handle the dependency in the cpufeature
stuff, we'll have other issues like this, but I'd like to handle that
separately since at first look doing it properly is a bit of surgery on
cpufeature and the series is already rather large.
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