Commit 3eb06f6c authored by Catalin Marinas's avatar Catalin Marinas
Browse files

arm64: cpufeature: Introduce MATCH_ALL_EARLY_CPUS capability type 



For system-wide capabilities, the kernel has the SCOPE_SYSTEM type. Such
capabilities are checked once the SMP boot has completed using the
sanitised ID registers. However, there is a need for a new capability
type similar in scope to the system one but with checking performed
locally on each CPU during boot (e.g. based on MIDR_EL1 which is not a
sanitised register).

Introduce ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS which, together with
ARM64_CPUCAP_SCOPE_LOCAL_CPU, ensures that such capability is enabled
only if all early CPUs have it. For ease of use, define
ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE which combines SCOPE_LOCAL_CPU,
PERMITTED_FOR_LATE_CPUS and MATCH_ALL_EARLY_CPUS.

Signed-off-by: default avatarMikołaj Lenczewski <miko.lenczewski@arm.com>
Reviewed-by: default avatarSuzuki K Poulose <Suzuki.Poulose@arm.com>
Link: https://lore.kernel.org/r/20250625113435.26849-2-miko.lenczewski@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 19272b37

arch/arm64/include/asm/cpufeature.h

+23 −0
Original line number Diff line number Diff line
@@ -275,6 +275,14 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; 
#define ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU	((u16)BIT(5))

/* Panic when a conflict is detected */

#define ARM64_CPUCAP_PANIC_ON_CONFLICT		((u16)BIT(6))

/*

 * When paired with SCOPE_LOCAL_CPU, all early CPUs must satisfy the

 * condition. This is different from SCOPE_SYSTEM where the check is performed

 * only once at the end of the SMP boot on the sanitised ID registers.

 * SCOPE_SYSTEM is not suitable for cases where the capability depends on

 * properties local to a CPU like MIDR_EL1.

 */

#define ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS	((u16)BIT(7))



/*

 * CPU errata workarounds that need to be enabled at boot time if one or
@@ -304,6 +312,16 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; 
	(ARM64_CPUCAP_SCOPE_LOCAL_CPU		|	\

	 ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU	|	\

	 ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU)

/*

 * CPU feature detected at boot time and present on all early CPUs. Late CPUs

 * are permitted to have the feature even if it hasn't been enabled, although

 * the feature will not be used by Linux in this case. If all early CPUs have

 * the feature, then every late CPU must have it.

 */

#define ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE		\

	 (ARM64_CPUCAP_SCOPE_LOCAL_CPU		|	\

	  ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU	|	\

	  ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS)



/*

 * CPU feature detected at boot time, on one or more CPUs. A late CPU
@@ -391,6 +409,11 @@ static inline int cpucap_default_scope(const struct arm64_cpu_capabilities *cap) 
	return cap->type & ARM64_CPUCAP_SCOPE_MASK;

}



static inline bool cpucap_match_all_early_cpus(const struct arm64_cpu_capabilities *cap)

{

	return cap->type & ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS;

}



/*

 * Generic helper for handling capabilities with multiple (match,enable) pairs

 * of call backs, sharing the same capability bit.

arch/arm64/kernel/cpufeature.c

+49 −11
Original line number Diff line number Diff line
@@ -3370,18 +3370,49 @@ static void update_cpu_capabilities(u16 scope_mask) 


	scope_mask &= ARM64_CPUCAP_SCOPE_MASK;

	for (i = 0; i < ARM64_NCAPS; i++) {

		bool match_all = false;

		bool caps_set = false;

		bool boot_cpu = false;



		caps = cpucap_ptrs[i];

		if (!caps || !(caps->type & scope_mask) ||

		    cpus_have_cap(caps->capability) ||

		    !caps->matches(caps, cpucap_default_scope(caps)))

		if (!caps || !(caps->type & scope_mask))

			continue;



		match_all = cpucap_match_all_early_cpus(caps);

		caps_set = cpus_have_cap(caps->capability);

		boot_cpu = scope_mask & SCOPE_BOOT_CPU;



		/*

		 * Unless it's a match-all CPUs feature, avoid probing if

		 * already detected.

		 */

		if (!match_all && caps_set)

			continue;



		if (caps->desc && !caps->cpus)

		/*

		 * A match-all CPUs capability is only set when probing the

		 * boot CPU. It may be cleared subsequently if not detected on

		 * secondary ones.

		 */

		if (match_all && !caps_set && !boot_cpu)

			continue;



		if (!caps->matches(caps, cpucap_default_scope(caps))) {

			if (match_all)

				__clear_bit(caps->capability, system_cpucaps);

			continue;

		}



		/*

		 * Match-all CPUs capabilities are logged later when the

		 * system capabilities are finalised.

		 */

		if (!match_all && caps->desc && !caps->cpus)

			pr_info("detected: %s\n", caps->desc);



		__set_bit(caps->capability, system_cpucaps);



		if ((scope_mask & SCOPE_BOOT_CPU) && (caps->type & SCOPE_BOOT_CPU))

		if (boot_cpu && (caps->type & SCOPE_BOOT_CPU))

			set_bit(caps->capability, boot_cpucaps);

	}

}
@@ -3782,17 +3813,24 @@ static void __init setup_system_capabilities(void) 
	enable_cpu_capabilities(SCOPE_ALL & ~SCOPE_BOOT_CPU);

	apply_alternatives_all();



	for (int i = 0; i < ARM64_NCAPS; i++) {

		const struct arm64_cpu_capabilities *caps = cpucap_ptrs[i];



		if (!caps || !caps->desc)

			continue;



		/*

		 * Log any cpucaps with a cpumask as these aren't logged by

		 * update_cpu_capabilities().

		 */

	for (int i = 0; i < ARM64_NCAPS; i++) {

		const struct arm64_cpu_capabilities *caps = cpucap_ptrs[i];



		if (caps && caps->cpus && caps->desc &&

			cpumask_any(caps->cpus) < nr_cpu_ids)

		if (caps->cpus && cpumask_any(caps->cpus) < nr_cpu_ids)

			pr_info("detected: %s on CPU%*pbl\n",

				caps->desc, cpumask_pr_args(caps->cpus));



		/* Log match-all CPUs capabilities */

		if (cpucap_match_all_early_cpus(caps) &&

		    cpus_have_cap(caps->capability))

			pr_info("detected: %s\n", caps->desc);

	}



	/*