[PATCH v2 01/36] KVM: arm64: Account for RES1 bits in DECLARE_FEAT_MAP() and co

[Jonathan Cameron]

On Fri, 19 Dec 2025 15:52:36 +0000
Sascha Bischoff <Sascha.Bischoff at arm.com> wrote:

> From: Marc Zyngier <maz at kernel.org>
> 
> None of the registers we manage in the feature dependency infrastructure
> so far has any RES1 bit. This is about to change, as VTCR_EL2 has
> its bit 31 being RES1.

Oh goody.

> 
> In order to not fail the consistency checks by not describing a bit,
> add RES1 bits to the set of immutable bits. This requires some extra
> surgery for the FGT handling, as we now need to track RES1 bits there
> as well.
> 
> There are no RES1 FGT bits *yet*. Watch this space.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
FWIW it seems correct.  The only thing I wondered about is
the assumption that if there is an error best thing to do is
to assume it was res0 that was wrong and paper over it.
I guess we can't do anything better if that does happen.

Reviewed-by: Jonathan Cameron <jonathan.cameron at huawei.com>

Process thing though: before anyone can merge this, Sasha
please take a look at submitting patches documentation.

When you 'post' a patch that was written by someone else you have
handled the patch and for the Developer Certificate of origin stuff
to work you have to add your Signed-off-by after theirs.

Jonathan