[PATCH] arm64: Allow CPUs unffected by ARM erratum 1418040 to come in late

[Will Deacon]

On Fri, Sep 11, 2020 at 07:16:11PM +0100, Marc Zyngier wrote:
> Now that we allow CPUs affected by erratum 1418040 to come in late,
> this prevents their unaffected sibblings from coming in late (or
> coming back after a suspend or hotplug-off, which amounts to the
> same thing).
> 
> To allow this, we need to add ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU,
> which amounts to set .type to ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE.
> 
> Reported-by: Doug Anderson <dianders at google.com>
> Tested-by: Sai Prakash Ranjan <saiprakash.ranjan at codeaurora.org>
> Fixes: bf87bb0881d0 ("arm64: Allow booting of late CPUs affected by erratum 1418040")
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kernel/cpu_errata.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index c332d49780dc..560ba69e13c1 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -910,8 +910,12 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>  		.desc = "ARM erratum 1418040",
>  		.capability = ARM64_WORKAROUND_1418040,
>  		ERRATA_MIDR_RANGE_LIST(erratum_1418040_list),
> -		.type = (ARM64_CPUCAP_SCOPE_LOCAL_CPU |
> -			 ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU),
> +		/*
> +		 * We need to allow affected CPUs to come in late, but
> +		 * also need the non-affected CPUs to be able to come
> +		 * in at any point in time. Wonderful.
> +		 */
> +		.type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,

Acked-by: Will Deacon <will at kernel.org>

Will