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

[Suzuki K Poulose]

On 02/03/2026 11:56, Marc Zyngier wrote:
> When computing the new value od an idreg that contains a field
> 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>
> ---
>   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;
> +

Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>



>   		if (ftr_cur == ftr_new)
>   			continue;
>   		/* Find a safe value */