[PATCH v2 01/11] arm64: Skip update of an idreg field affected by an override

[Fuad Tabba]

Hi Marc,

On Mon, 2 Mar 2026 at 11:57, Marc Zyngier <maz at kernel.org> wrote:
>
> When computing the new value od an idreg that contains a field

nit: od->of

> affected by an override, do not update that particular field.
>
> The value computed at init-time must be kept as-is, as that's
> what the user has asked for, for better or worse.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>

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

Cheers,
/fuad


> ---
>  arch/arm64/kernel/cpufeature.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index c31f8e17732a3..28fc77443ccd3 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1224,6 +1224,13 @@ static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new)
>                 s64 ftr_cur = arm64_ftr_value(ftrp, reg->sys_val);
>                 s64 ftr_new = arm64_ftr_value(ftrp, new);
>
> +               /*
> +                * Don't alter the initial value that has been forced
> +                * by an override.
> +                */
> +               if ((reg->override->mask & arm64_ftr_mask(ftrp)) == arm64_ftr_mask(ftrp))
> +                       continue;
> +
>                 if (ftr_cur == ftr_new)
>                         continue;
>                 /* Find a safe value */
> --
> 2.47.3
>