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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: Mikołaj Lenczewski <miko.lenczewski@arm.com>
Reviewed-by: Suzuki K Poulose <Suzuki.Poulose@arm.com>
Link: https://lore.kernel.org/r/20250625113435.26849-2-miko.lenczewski@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Catalin Marinas 2025-06-25 11:34:32 +00:00
parent 19272b37aa
commit 3eb06f6ce3
2 changed files with 72 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
arch/arm64/include/asm/cpufeature.h
View File

@ -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.

58
arch/arm64/kernel/cpufeature.c
View File

@ -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;
if (caps->desc && !caps->cpus)
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;
/*
* 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);
}
/*