[PATCH 08/16] arm64: capabilities: Group handling of features and errata

[Dave.Martin@arm.com (Dave Martin)]

On Tue, Jan 23, 2018 at 12:28:01PM +0000, Suzuki K Poulose wrote:
> So far we have had separate routes for triggering errata and feature

"triggering errata" ? ;)

Maybe "[...] for determining whether to activate errata workarounds and
whether to enable feature capabilities."

> capabilities. Also, we never allowed "features" based on local CPU
> and "errata" based on System wide safe registers. This patch
> groups the handling of errata and features and also allows them
> to have all the possible scopes.
> 
> So, we now run through the arm64_features and arm64_errata:

when?

What about late cpus?

>  1) with SCOPE_LOCAL_CPU filter on each boot time enabeld CPUs,
>     via update_cpu_local_capabilities().

"each [...] enabeld CPUs" -> "each [...] enabled CPU".

Also, changing "boot time" -> "boot-time" helps avoid this being misread
as "on each boot", which could be taken to mean "each time a CPU comes
online".  I'm guessing that's not the intended meaning here.

>  2) with SCOPE_SYSTEM filter only once after all boot time enabled
>     CPUs are active.
> 
> We could ideally merge the two tables into one. But leave it as
> it is for easy access to the list of particular type.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
>  arch/arm64/kernel/cpufeature.c | 77 ++++++++++++++++++++++++------------------
>  1 file changed, 44 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 198c5daddd65..7ae5cf9092d0 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -504,7 +504,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
>  }
>  
>  extern const struct arm64_cpu_capabilities arm64_errata[];
> -static void update_cpu_errata_workarounds(void);
> +static void update_cpu_local_capabilities(void);
>  
>  void __init init_cpu_features(struct cpuinfo_arm64 *info)
>  {
> @@ -553,7 +553,7 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info)
>  	 * Run the errata work around checks on the boot CPU, once we have
>  	 * initialised the cpu feature infrastructure.
>  	 */
> -	update_cpu_errata_workarounds();
> +	update_cpu_local_capabilities();
>  }
>  
>  static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new)
> @@ -1179,8 +1179,8 @@ static bool __this_cpu_has_cap(const struct arm64_cpu_capabilities *cap_array,
>  	return false;
>  }
>  
> -static void update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
> -				    u16 cap_type, const char *info)
> +static void __update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
> +				      u16 cap_type, const char *info)
>  {
>  	for (; caps->matches; caps++) {
>  		if (!(caps->type & cap_type))
> @@ -1194,6 +1194,13 @@ static void update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
>  	}
>  }
>  
> +static void update_cpu_capabilities(u16 type)
> +{
> +	__update_cpu_capabilities(arm64_features, type,
> +				"detected feature:");
> +	__update_cpu_capabilities(arm64_errata, type,
> +				"enabling work around for");
> +}
>  
>  static int __enable_cpu_capability(void *arg)
>  {
> @@ -1207,7 +1214,7 @@ static int __enable_cpu_capability(void *arg)
>   * CPUs
>   */
>  static void __init
> -enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps, u16 caps_type)
> +__enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps, u16 caps_type)
>  {
>  	for (; caps->matches; caps++) {
>  		unsigned int num = caps->capability;
> @@ -1282,6 +1289,12 @@ static bool __verify_local_cpu_caps(const struct arm64_cpu_capabilities *caps_li
>  	return true;
>  }
>  
> +static bool verify_local_cpu_caps(u16 type)
> +{
> +	return __verify_local_cpu_caps(arm64_features, type) &&
> +	       __verify_local_cpu_caps(arm64_errata, type);
> +}
> +
>  /*
>   * Check for CPU features that are used in early boot
>   * based on the Boot CPU value.
> @@ -1304,12 +1317,6 @@ verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps)
>  		}
>  }
>  
> -static void verify_local_cpu_features(void)
> -{
> -	if (!__verify_local_cpu_caps(arm64_features, ARM64_CPUCAP_TYPE_ALL))
> -		cpu_die_early();
> -}
> -
>  static void verify_sve_features(void)
>  {
>  	u64 safe_zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1);
> @@ -1328,26 +1335,28 @@ static void verify_sve_features(void)
>  }
>  
>  /*
> - * The CPU Errata work arounds are detected and applied at boot time
> - * and the related information is freed soon after. If the new CPU requires
> - * an errata not detected at boot, fail this CPU.
> + * Check for all capablities within the scope of local CPU.
> + * This is run on all boot time activated CPUs.
>   */
> -static void verify_local_cpu_errata_workarounds(void)
> +static void update_cpu_local_capabilities(void)

[Gaah, stupid git diff making function insertion look like function
modification.  Sometimes --patience does a better job, but there seems
no foolproof solution...  If you do a respin, it might be worth trying
it.]

>  {
> -	if (!__verify_local_cpu_caps(arm64_errata, ARM64_CPUCAP_TYPE_ALL))
> -		cpu_die_early();
> +	update_cpu_capabilities(ARM64_CPUCAP_SCOPE_LOCAL_CPU);
>  }
>  
> -static void update_cpu_errata_workarounds(void)
> +/*
> + * Check for all capablities with a system wide scope.
> + * This is run only once after all the boot CPUs are
> + * brought online.
> + */
> +static void update_system_capabilities(void)
>  {
> -	update_cpu_capabilities(arm64_errata,
> -				ARM64_CPUCAP_TYPE_ALL,
> -				"enabling workaround for");
> +	update_cpu_capabilities(ARM64_CPUCAP_SCOPE_SYSTEM);
>  }
>  
> -static void __init enable_errata_workarounds(void)
> +static void enable_cpu_capabilities(u16 type)
>  {
> -	enable_cpu_capabilities(arm64_errata, ARM64_CPUCAP_TYPE_ALL);
> +	__enable_cpu_capabilities(arm64_errata, type);
> +	__enable_cpu_capabilities(arm64_features, type);
>  }
>  
>  /*
> @@ -1360,8 +1369,8 @@ static void __init enable_errata_workarounds(void)
>   */
>  static void verify_local_cpu_capabilities(void)
>  {
> -	verify_local_cpu_errata_workarounds();
> -	verify_local_cpu_features();
> +	if (!verify_local_cpu_caps(ARM64_CPUCAP_TYPE_ALL))
> +		cpu_die_early();
>  	verify_local_elf_hwcaps(arm64_elf_hwcaps);
>  
>  	if (system_supports_32bit_el0())
> @@ -1389,16 +1398,20 @@ void check_local_cpu_capabilities(void)
>  	 * advertised capabilities.
>  	 */
>  	if (!sys_caps_initialised)
> -		update_cpu_errata_workarounds();
> +		update_cpu_local_capabilities();
>  	else
>  		verify_local_cpu_capabilities();
>  }
>  
> -static void __init setup_feature_capabilities(void)
> +static void __init setup_system_capabilities(void)
>  {
> -	update_cpu_capabilities(arm64_features,
> -				ARM64_CPUCAP_TYPE_ALL, "detected feature:");
> -	enable_cpu_capabilities(arm64_features, ARM64_CPUCAP_TYPE_ALL);
> +	/*
> +	 * We have finalised the system wide safe feature registers,
> +	 * finalise the capabilities that depend on it.
> +	 */
> +	update_system_capabilities();
> +	/* Enable all the available capabilities */
> +	enable_cpu_capabilities(ARM64_CPUCAP_TYPE_ALL);

So setup_system_capabilities() enables _non_ system-wide capabilities/
errata workarounds too?

Maybe this function should just have a different name, like
"setup_boot_capabilities" or similar?

  }
>  
>  DEFINE_STATIC_KEY_FALSE(arm64_const_caps_ready);
> @@ -1422,9 +1435,7 @@ void __init setup_cpu_features(void)
>  	u32 cwg;
>  	int cls;
>  
> -	/* Set the CPU feature capabilies */
> -	setup_feature_capabilities();
> -	enable_errata_workarounds();
> +	setup_system_capabilities();
>  	mark_const_caps_ready();
>  	setup_elf_hwcaps(arm64_elf_hwcaps);

I wonder whether we could unify the elf hwcaps handling too.

That's not necessary for this series though.

Cheers
---Dave