Re: [PATCH v4 00/17] kvm/arm: Introduce a customizable aarch64 KVM host model

[Marc Zyngier <maz@kernel.org>]

On Fri, 15 May 2026 09:31:19 +0100,
Peter Maydell <peter.maydell@linaro.org> wrote:
> 
> So if the user asks to set ID registers to an architecturally
> invalid combination (e.g. one that reports FEAT_X but not
> FEAT_Y even though FEAT_X is supposed to imply FEAT_Y, or
> one where one ID register says we have FEAT_X but a different
> ID register says we don't have FEAT_X), what happens ?
> Do we catch and reject that? Does the kernel reject that?
> Or do we just report to the guest what the user asked for,
> and if they asked for something broken they can keep both
> pieces ?

I fully expect the latter. Neither the kernel nor QEMU can enforce
this short of encoding all the various dependencies, which have the
horrible habit of changing over time. The only thing we can
realistically reason about is a single idreg at a time.

Thanks,

	M.

-- 
Jazz isn't dead. It just smells funny.