Message-ID: <20180207103829.GY5862@e103592.cambridge.arm.com>
Date:   Wed, 7 Feb 2018 10:38:29 +0000
From:   Dave Martin <Dave.Martin@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
        ckadabi@...eaurora.org, ard.biesheuvel@...aro.org,
        marc.zyngier@....com, catalin.marinas@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org, jnair@...iumnetworks.com,
        dave.martin@....com
Subject: Re: [PATCH v2 08/20] arm64: capabilities: Group handling of features
 and errata

On Wed, Jan 31, 2018 at 06:27:55PM +0000, Suzuki K Poulose wrote:
> So far we have had separate routes for triggering errata and feature
> capability detection. 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 both
> arm64_features and arm64_errata, in two phases for detection.
> 
>  1) with SCOPE_LOCAL_CPU filter on each boot time enabled CPUs,
>     via update_cpu_local_capabilities().
> 
>  2) with SCOPE_SYSTEM filter only once after all boot time enabled
>     CPUs are active, triggered from setup_cpu_features().
> 
> A late CPU goes through both the tables for verification against
> established capabilities, as before.
> 
> We could ideally merge the two tables into one. But leave it as
> it is for easy access to the list of particular type.
> 
> Cc: Dave Martin <dave.martin@....com>
> Cc: Will Deacon <will.deacon@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>

I don't know if there's a way of splitting or refactoring this patch to
make it easier to understand the changes, but I think I get what's going
on here now.

So,

Reviewed-by: Dave Martin <Dave.Martin@....com>

(But if you can see a good way to split it, I'll be happy to take
another look.)

> ---
>  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 5163dc51b975..c710ef28524e 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)
> @@ -1184,8 +1184,8 @@ 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 scope_mask, const char *info)
> +static void __update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
> +				      u16 scope_mask, const char *info)
>  {
>  	scope_mask &= ARM64_CPUCAP_SCOPE_MASK;
>  	for (; caps->matches; caps++) {
> @@ -1199,6 +1199,13 @@ static void update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
>  	}
>  }
>  
> +static void update_cpu_capabilities(u16 scope_mask)
> +{
> +	__update_cpu_capabilities(arm64_features, scope_mask,
> +				"detected feature:");
> +	__update_cpu_capabilities(arm64_errata, scope_mask,
> +				"enabling work around for");
> +}
>  
>  static int __enable_cpu_capability(void *arg)
>  {
> @@ -1213,7 +1220,7 @@ static int __enable_cpu_capability(void *arg)
>   * CPUs
>   */
>  static void __init
> -enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps, u16 scope_mask)
> +__enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps, u16 scope_mask)
>  {
>  	scope_mask &= ARM64_CPUCAP_SCOPE_MASK;
>  	for (; caps->matches; caps++) {
> @@ -1293,6 +1300,12 @@ static bool __verify_local_cpu_caps(const struct arm64_cpu_capabilities *caps_li
>  	return true;
>  }
>  
> +static bool verify_local_cpu_caps(u16 scope_mask)
> +{
> +	return __verify_local_cpu_caps(arm64_features, scope_mask) &&
> +	       __verify_local_cpu_caps(arm64_errata, scope_mask);
> +}
> +
>  /*
>   * Check for CPU features that are used in early boot
>   * based on the Boot CPU value.
> @@ -1315,12 +1328,6 @@ 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_SCOPE_ALL))
> -		cpu_die_early();
> -}
> -
>  static void verify_sve_features(void)
>  {
>  	u64 safe_zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1);
> @@ -1339,26 +1346,28 @@ 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)
>  {
> -	if (!__verify_local_cpu_caps(arm64_errata, ARM64_CPUCAP_SCOPE_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_SCOPE_ALL,
> -				"enabling workaround for");
> +	update_cpu_capabilities(ARM64_CPUCAP_SCOPE_SYSTEM);
>  }
>  
> -static void __init enable_errata_workarounds(void)
> +static void enable_cpu_capabilities(u16 scope_mask)
>  {
> -	enable_cpu_capabilities(arm64_errata, ARM64_CPUCAP_SCOPE_ALL);
> +	__enable_cpu_capabilities(arm64_errata, scope_mask);
> +	__enable_cpu_capabilities(arm64_features, scope_mask);
>  }
>  
>  /*
> @@ -1371,8 +1380,8 @@ 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_SCOPE_ALL))
> +		cpu_die_early();
>  	verify_local_elf_hwcaps(arm64_elf_hwcaps);
>  
>  	if (system_supports_32bit_el0())
> @@ -1400,16 +1409,20 @@ 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_SCOPE_ALL, "detected feature:");
> -	enable_cpu_capabilities(arm64_features, ARM64_CPUCAP_SCOPE_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_SCOPE_ALL);
>  }
>  
>  DEFINE_STATIC_KEY_FALSE(arm64_const_caps_ready);
> @@ -1433,9 +1446,7 @@ 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);
>  
> -- 
> 2.14.3
> 
> 
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> linux-arm-kernel@...ts.infradead.org
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