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Subject[PATCH v2 1/6] arm64: add support for the AMU extension v1
Date
The activity monitors extension is an optional extension introduced
by the ARMv8.4 CPU architecture. This implements basic support for
version 1 of the activity monitors architecture, AMUv1.

This support includes:
- Extension detection on each CPU (boot, secondary, hotplugged)
- Register interface for AMU aarch64 registers
- (while here) create defines for ID_PFR0_EL1 fields when adding
the AMU field information.

Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
---
arch/arm64/Kconfig | 27 ++++++++++
arch/arm64/include/asm/cpucaps.h | 3 +-
arch/arm64/include/asm/cpufeature.h | 4 ++
arch/arm64/include/asm/sysreg.h | 44 ++++++++++++++++
arch/arm64/kernel/cpufeature.c | 81 +++++++++++++++++++++++++++--
5 files changed, 154 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ac31ed6184d0..6ae7bfa5812e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1485,6 +1485,33 @@ config ARM64_PTR_AUTH

endmenu

+menu "ARMv8.4 architectural features"
+
+config ARM64_AMU_EXTN
+ bool "Enable support for the Activity Monitors Unit CPU extension"
+ default y
+ help
+ The activity monitors extension is an optional extension introduced
+ by the ARMv8.4 CPU architecture. This enables support for version 1
+ of the activity monitors architecture, AMUv1.
+
+ To enable the use of this extension on CPUs that implement it, say Y.
+
+ Note that for architectural reasons, firmware _must_ implement AMU
+ support when running on CPUs that present the activity monitors
+ extension. The required support is present in:
+ * Version 1.5 and later of the ARM Trusted Firmware
+
+ For kernels that have this configuration enabled but boot with broken
+ firmware, you may need to say N here until the firmware is fixed.
+ Otherwise you may experience firmware panics or lockups when
+ accessing the counter registers. Even if you are not observing these
+ symptoms, the values returned by the register reads might not
+ correctly reflect reality. Most commonly, the value read will be 0,
+ indicating that the counter is not enabled.
+
+endmenu
+
config ARM64_SVE
bool "ARM Scalable Vector Extension support"
default y
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index b92683871119..7dde890bde50 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -56,7 +56,8 @@
#define ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM 46
#define ARM64_WORKAROUND_1542419 47
#define ARM64_WORKAROUND_1319367 48
+#define ARM64_HAS_AMU_EXTN 49

-#define ARM64_NCAPS 49
+#define ARM64_NCAPS 50

#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 4261d55e8506..b89e799d6972 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -673,6 +673,10 @@ static inline bool cpu_has_hw_af(void)
ID_AA64MMFR1_HADBS_SHIFT);
}

+#ifdef CONFIG_ARM64_AMU_EXTN
+extern inline bool cpu_has_amu_feat(void);
+#endif
+
#endif /* __ASSEMBLY__ */

#endif
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 6e919fafb43d..bfcc87953a68 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -382,6 +382,42 @@
#define SYS_TPIDR_EL0 sys_reg(3, 3, 13, 0, 2)
#define SYS_TPIDRRO_EL0 sys_reg(3, 3, 13, 0, 3)

+/* Definitions for system register interface to AMU for ARMv8.4 onwards */
+#define SYS_AM_EL0(crm, op2) sys_reg(3, 3, 13, crm, op2)
+#define SYS_AMCR_EL0 SYS_AM_EL0(2, 0)
+#define SYS_AMCFGR_EL0 SYS_AM_EL0(2, 1)
+#define SYS_AMCGCR_EL0 SYS_AM_EL0(2, 2)
+#define SYS_AMUSERENR_EL0 SYS_AM_EL0(2, 3)
+#define SYS_AMCNTENCLR0_EL0 SYS_AM_EL0(2, 4)
+#define SYS_AMCNTENSET0_EL0 SYS_AM_EL0(2, 5)
+#define SYS_AMCNTENCLR1_EL0 SYS_AM_EL0(3, 0)
+#define SYS_AMCNTENSET1_EL0 SYS_AM_EL0(3, 1)
+
+/*
+ * Group 0 of activity monitors (architected):
+ * op0 CRn op1 op2 CRm
+ * Counter: 11 1101 011 n<2:0> 010:n<3>
+ * Type: 11 1101 011 n<2:0> 011:n<3>
+ * n: 0-3
+ *
+ * Group 1 of activity monitors (auxiliary):
+ * op0 CRn op1 op2 CRm
+ * Counter: 11 1101 011 n<2:0> 110:n<3>
+ * Type: 11 1101 011 n<2:0> 111:n<3>
+ * n: 0-15
+ */
+
+#define SYS_AMEVCNTR0_EL0(n) SYS_AM_EL0(4 + ((n) >> 3), (n) & 0x7)
+#define SYS_AMEVTYPE0_EL0(n) SYS_AM_EL0(6 + ((n) >> 3), (n) & 0x7)
+#define SYS_AMEVCNTR1_EL0(n) SYS_AM_EL0(12 + ((n) >> 3), (n) & 0x7)
+#define SYS_AMEVTYPE1_EL0(n) SYS_AM_EL0(14 + ((n) >> 3), (n) & 0x7)
+
+/* V1: Fixed (architecturally defined) activity monitors */
+#define SYS_AMEVCNTR0_CORE_EL0 SYS_AMEVCNTR0_EL0(0)
+#define SYS_AMEVCNTR0_CONST_EL0 SYS_AMEVCNTR0_EL0(1)
+#define SYS_AMEVCNTR0_INST_RET_EL0 SYS_AMEVCNTR0_EL0(2)
+#define SYS_AMEVCNTR0_MEM_STALL SYS_AMEVCNTR0_EL0(3)
+
#define SYS_CNTFRQ_EL0 sys_reg(3, 3, 14, 0, 0)

#define SYS_CNTP_TVAL_EL0 sys_reg(3, 3, 14, 2, 0)
@@ -577,6 +613,7 @@
#define ID_AA64PFR0_CSV3_SHIFT 60
#define ID_AA64PFR0_CSV2_SHIFT 56
#define ID_AA64PFR0_DIT_SHIFT 48
+#define ID_AA64PFR0_AMU_SHIFT 44
#define ID_AA64PFR0_SVE_SHIFT 32
#define ID_AA64PFR0_RAS_SHIFT 28
#define ID_AA64PFR0_GIC_SHIFT 24
@@ -587,6 +624,7 @@
#define ID_AA64PFR0_EL1_SHIFT 4
#define ID_AA64PFR0_EL0_SHIFT 0

+#define ID_AA64PFR0_AMU 0x1
#define ID_AA64PFR0_SVE 0x1
#define ID_AA64PFR0_RAS_V1 0x1
#define ID_AA64PFR0_FP_NI 0xf
@@ -709,6 +747,12 @@
#define ID_AA64MMFR0_TGRAN16_NI 0x0
#define ID_AA64MMFR0_TGRAN16_SUPPORTED 0x1

+#define ID_PFR0_AMU_SHIFT 20
+#define ID_PFR0_STATE3_SHIFT 12
+#define ID_PFR0_STATE2_SHIFT 8
+#define ID_PFR0_STATE1_SHIFT 4
+#define ID_PFR0_STATE0_SHIFT 0
+
#if defined(CONFIG_ARM64_4K_PAGES)
#define ID_AA64MMFR0_TGRAN_SHIFT ID_AA64MMFR0_TGRAN4_SHIFT
#define ID_AA64MMFR0_TGRAN_SUPPORTED ID_AA64MMFR0_TGRAN4_SUPPORTED
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 04cf64e9f0c9..c639b3e052d7 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -156,6 +156,7 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV2_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_DIT_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_AMU_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_RAS_SHIFT, 4, 0),
@@ -314,10 +315,11 @@ static const struct arm64_ftr_bits ftr_id_mmfr4[] = {
};

static const struct arm64_ftr_bits ftr_id_pfr0[] = {
- ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 12, 4, 0), /* State3 */
- ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 8, 4, 0), /* State2 */
- ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 4, 4, 0), /* State1 */
- ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 0, 4, 0), /* State0 */
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR0_AMU_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR0_STATE3_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR0_STATE2_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR0_STATE1_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR0_STATE0_SHIFT, 4, 0),
ARM64_FTR_END,
};

@@ -1150,6 +1152,59 @@ static bool has_hw_dbm(const struct arm64_cpu_capabilities *cap,

#endif

+#ifdef CONFIG_ARM64_AMU_EXTN
+
+/*
+ * This per cpu variable only signals that the CPU implementation supports
+ * the Activity Monitors Unit (AMU) but does not provide information
+ * regarding all the events that it supports.
+ * When this amu_feat per CPU variable is true, the user of this feature
+ * can only rely on the presence of the 4 fixed counters. But this does
+ * not guarantee that the counters are enabled or access to these counters
+ * is provided by code executed at higher exception levels.
+ *
+ * Also, to ensure the safe use of this per_cpu variable, the following
+ * accessor is defined to allow a read of amu_feat for the current cpu only
+ * from the current cpu.
+ * - cpu_has_amu_feat()
+ */
+static DEFINE_PER_CPU_READ_MOSTLY(u8, amu_feat);
+
+inline bool cpu_has_amu_feat(void)
+{
+ return !!this_cpu_read(amu_feat);
+}
+
+static void cpu_amu_enable(struct arm64_cpu_capabilities const *cap)
+{
+ if (has_cpuid_feature(cap, SCOPE_LOCAL_CPU)) {
+ pr_info("detected CPU%d: Activity Monitors Unit (AMU)\n",
+ smp_processor_id());
+ this_cpu_write(amu_feat, 1);
+ }
+}
+
+static bool has_amu(const struct arm64_cpu_capabilities *cap,
+ int __unused)
+{
+ /*
+ * The AMU extension is a non-conflicting feature: the kernel can
+ * safely run a mix of CPUs with and without support for the
+ * activity monitors extension.
+ * Therefore, unconditionally enable the capability to allow
+ * any late CPU to use the feature.
+ *
+ * With this feature unconditionally enabled, the cpu_enable
+ * function will be called for all CPUs that match the criteria,
+ * including secondary and hotplugged, marking this feature as
+ * present on that respective CPU. The enable function will also
+ * print a detection message.
+ */
+
+ return true;
+}
+#endif
+
#ifdef CONFIG_ARM64_VHE
static bool runs_at_el2(const struct arm64_cpu_capabilities *entry, int __unused)
{
@@ -1419,6 +1474,24 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.cpu_enable = cpu_clear_disr,
},
#endif /* CONFIG_ARM64_RAS_EXTN */
+#ifdef CONFIG_ARM64_AMU_EXTN
+ {
+ /*
+ * The feature is enabled by default if CONFIG_ARM64_AMU_EXTN=y.
+ * Therefore, don't provide .desc as we don't want the detection
+ * message to be shown until at least one CPU is detected to
+ * support the feature.
+ */
+ .capability = ARM64_HAS_AMU_EXTN,
+ .type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
+ .matches = has_amu,
+ .sys_reg = SYS_ID_AA64PFR0_EL1,
+ .sign = FTR_UNSIGNED,
+ .field_pos = ID_AA64PFR0_AMU_SHIFT,
+ .min_field_value = ID_AA64PFR0_AMU,
+ .cpu_enable = cpu_amu_enable,
+ },
+#endif /* CONFIG_ARM64_AMU_EXTN */
{
.desc = "Data cache clean to the PoU not required for I/D coherence",
.capability = ARM64_HAS_CACHE_IDC,
--
2.17.1
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