Detect Statistical Profiling Extension (SPE) support using the cpufeatures
framework. The presence of SPE is reported via the ARM64_SPE capability.
The feature will be necessary for emulating SPE in KVM, because KVM needs
that all CPUs have SPE hardware to avoid scheduling a VCPU on a CPU without
support. For this reason, the feature type ARM64_CPUCAP_SYSTEM_FEATURE has
been selected to disallow hotplugging a CPU which doesn't support SPE.
Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
---
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/kernel/cpufeature.c | 24 ++++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 42868dbd29fd..10fd094d9a5b 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -65,7 +65,8 @@
#define ARM64_HAS_ARMv8_4_TTL 55
#define ARM64_HAS_TLB_RANGE 56
#define ARM64_MTE 57
+#define ARM64_SPE 58
-#define ARM64_NCAPS 58
+#define ARM64_NCAPS 59
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index dcc165b3fc04..4a0f4dc53824 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1278,6 +1278,18 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope)
return has_cpuid_feature(entry, scope);
}
+static bool __maybe_unused
+has_usable_spe(const struct arm64_cpu_capabilities *entry, int scope)
+{
+ u64 pmbidr;
+
+ if (!has_cpuid_feature(entry, scope))
+ return false;
+
+ pmbidr = read_sysreg_s(SYS_PMBIDR_EL1);
+ return !(pmbidr & BIT(SYS_PMBIDR_EL1_P_SHIFT));
+}
+
/*
* This check is triggered during the early boot before the cpufeature
* is initialised. Checking the status on the local CPU allows the boot
@@ -2003,6 +2015,18 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.min_field_value = 1,
.cpu_enable = cpu_enable_cnp,
},
+#endif
+#ifdef CONFIG_ARM_SPE_PMU
+ {
+ .desc = "Statistical Profiling Extension (SPE)",
+ .capability = ARM64_SPE,
+ .type = ARM64_CPUCAP_SYSTEM_FEATURE,
+ .matches = has_usable_spe,
+ .sys_reg = SYS_ID_AA64DFR0_EL1,
+ .sign = FTR_UNSIGNED,
+ .field_pos = ID_AA64DFR0_PMSVER_SHIFT,
+ .min_field_value = 1,
+ },
#endif
{
.desc = "Speculation barrier (SB)",
--
2.29.1
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