[PATCH v2 10/13] arm64: Add MIDR-based override infrastructure

[Suzuki K Poulose]

On 20/11/2023 12:37, Marc Zyngier wrote:
> In order to be able to use the override infrastructure to "fix"
> CPUs that have deviated from teh architecture spec, add a new
> pile of hacks on top of the existing one, allowing a feature
> to be overriden based on matching a MIDR list.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>

Nice idea!

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

> ---
>   arch/arm64/kernel/idreg-override.c | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
> 
> diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> index 7b5b9dc20e6b..57c145bf50b7 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -321,6 +321,23 @@ static __init void parse_cmdline(void)
>   		__parse_cmdline(prop, true);
>   }
>   
> +struct midr_override_data {
> +	const char		feature[FTR_ALIAS_OPTION_LEN];
> +	const struct midr_range	ranges[];
> +};
> +
> +static const struct midr_override_data * const midr_ovr_data[] __initconst = {
> +};
> +
> +static void __init apply_midr_overrides(void)
> +{
> +	const u64 midr = read_cpuid_id();
> +
> +	for (int i = 0; i < ARRAY_SIZE(midr_ovr_data); i++)
> +		if (is_midr_in_range_list(midr, midr_ovr_data[i]->ranges))
> +			__parse_cmdline(midr_ovr_data[i]->feature, false);
> +}
> +
>   /* Keep checkers quiet */
>   void init_feature_override(u64 boot_status);
>   
> @@ -337,6 +354,8 @@ asmlinkage void __init init_feature_override(u64 boot_status)
>   
>   	__boot_status = boot_status;
>   
> +	apply_midr_overrides();
> +
>   	parse_cmdline();
>   
>   	for (i = 0; i < ARRAY_SIZE(regs); i++) {