[RFC PATCH v3 04/16] arm64: Introduce CPU SPE feature
From: Alexandru Elisei <hidden>
Date: 2020-10-27 17:27:15
Also in:
kvmarm
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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 <redacted> --- 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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