[PATCH 07/20] KVM: arm64: Allow RES1 bits to be inferred from configuration

[Fuad Tabba]

On Mon, 26 Jan 2026 at 12:17, Marc Zyngier <maz at kernel.org> wrote:
>
> So far, when a bit field is tied to an unsupported feature, we set
> it as RES0. This is almost forrect, but there are a few exceptions
> where the bits become RES1.

You need to correct forrect :)

> Add a AS_RES1 qualifier that instruct the RESx computing code to
> simply do that.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/config.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
> index 8d152605999ba..6a4674fabf865 100644
> --- a/arch/arm64/kvm/config.c
> +++ b/arch/arm64/kvm/config.c
> @@ -24,6 +24,7 @@ struct reg_bits_to_feat_map {
>  #define        CALL_FUNC       BIT(1)  /* Needs to evaluate tons of crap */
>  #define        FIXED_VALUE     BIT(2)  /* RAZ/WI or RAO/WI in KVM */
>  #define        MASKS_POINTER   BIT(3)  /* Pointer to fgt_masks struct instead of bits */
> +#define        AS_RES1         BIT(4)  /* RES1 when not supported */
>
>         unsigned long   flags;
>
> @@ -1316,8 +1317,12 @@ struct resx __compute_fixed_bits(struct kvm *kvm,
>                 else
>                         match = idreg_feat_match(kvm, &map[i]);
>
> -               if (!match || (map[i].flags & FIXED_VALUE))
> -                       resx.res0 |= reg_feat_map_bits(&map[i]);
> +               if (!match || (map[i].flags & FIXED_VALUE)) {
> +                       if (map[i].flags & AS_RES1)
> +                               resx.res1 |= reg_feat_map_bits(&map[i]);
> +                       else
> +                               resx.res0 |= reg_feat_map_bits(&map[i]);
> +               }

checkpatch is complaining about whitespaces here. I can't blame it.

With those fixed, looks good to me.

Reviewed-by: Fuad Tabba <tabba at google.com>

Cheers,
/fuad

>         }
>
>         return resx;



> --
> 2.47.3
>