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Subject[PATCH v5 10/27] arm64: cpufeature: Add cpufeature for IRQ priority masking
Date
Add a cpufeature indicating whether a cpu supports masking interrupts
by priority.

Add command line option to disable that feature at runtime.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +++
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/kernel/cpufeature.c | 31 +++++++++++++++++++++++++
3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9871e64..d3e1170 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2764,6 +2764,9 @@
noexec=on: enable non-executable mappings (default)
noexec=off: disable non-executable mappings

+ nogicprios [ARM64]
+ Disable usage of GIC priorities to toggle interrupt status.
+
nosmap [X86]
Disable SMAP (Supervisor Mode Access Prevention)
even if it is supported by processor.
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index ae1f704..8cc2ae5 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -51,7 +51,8 @@
#define ARM64_SSBD 30
#define ARM64_MISMATCHED_CACHE_TYPE 31
#define ARM64_HAS_STAGE2_FWB 32
+#define ARM64_HAS_IRQ_PRIO_MASKING 33

-#define ARM64_NCAPS 33
+#define ARM64_NCAPS 34

#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 0d1e41e..2f2c557 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1046,6 +1046,22 @@ static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused)
WARN_ON(val & (7 << 27 | 7 << 21));
}

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+static bool nogicprios = false;
+
+static int __init early_nogicprios(char *p)
+{
+ nogicprios = true;
+ return 0;
+}
+early_param("nogicprios", early_nogicprios);
+
+static bool can_use_gic_priorities(const struct arm64_cpu_capabilities *entry, int scope)
+{
+ return !nogicprios && has_useable_gicv3_cpuif(entry, scope);
+}
+#endif
+
static const struct arm64_cpu_capabilities arm64_features[] = {
{
.desc = "GIC system register CPU interface",
@@ -1233,6 +1249,21 @@ static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused)
.cpu_enable = cpu_enable_hw_dbm,
},
#endif
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ {
+ /*
+ * Depends on having GICv3
+ */
+ .desc = "IRQ priority masking",
+ .capability = ARM64_HAS_IRQ_PRIO_MASKING,
+ .type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
+ .matches = can_use_gic_priorities,
+ .sys_reg = SYS_ID_AA64PFR0_EL1,
+ .field_pos = ID_AA64PFR0_GIC_SHIFT,
+ .sign = FTR_UNSIGNED,
+ .min_field_value = 1,
+ },
+#endif
{},
};

--
1.9.1
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