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Message-ID: <20250617095104.6772-2-miko.lenczewski@arm.com>
Date: Tue, 17 Jun 2025 09:51:01 +0000
From: Mikołaj Lenczewski <miko.lenczewski@....com>
To: ryan.roberts@....com,
yang@...amperecomputing.com,
catalin.marinas@....com,
will@...nel.org,
jean-philippe@...aro.org,
robin.murphy@....com,
joro@...tes.org,
maz@...nel.org,
oliver.upton@...ux.dev,
joey.gouly@....com,
james.morse@....com,
broonie@...nel.org,
ardb@...nel.org,
baohua@...nel.org,
suzuki.poulose@....com,
david@...hat.com,
jgg@...pe.ca,
nicolinc@...dia.com,
jsnitsel@...hat.com,
mshavit@...gle.com,
kevin.tian@...el.com,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org,
iommu@...ts.linux.dev
Cc: Mikołaj Lenczewski <miko.lenczewski@....com>,
Suzuki K Poulose <Suzuki.Poulose@....com>
Subject: [PATCH v7 1/4] arm64: cpufeature: Introduce MATCH_ALL_EARLY_CPUS capability type
From: Catalin Marinas <catalin.marinas@....com>
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: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Mikołaj Lenczewski <miko.lenczewski@....com>
Cc: Suzuki K Poulose <Suzuki.Poulose@....com>
---
arch/arm64/include/asm/cpufeature.h | 23 +++++++++++
arch/arm64/kernel/cpufeature.c | 60 +++++++++++++++++++++++------
2 files changed, 72 insertions(+), 11 deletions(-)
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index c4326f1cb917..155ebd040c55 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -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.
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b34044e20128..f9c947166322 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -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();
- /*
- * 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 || !caps->desc)
+ continue;
+
+ /*
+ * Log any cpucaps with a cpumask as these aren't logged by
+ * update_cpu_capabilities().
+ */
+ 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);
}
/*
--
2.49.0
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