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Subject[PATCH v6 1/7] arm64: cpufeature: Detect CPU RAS Extentions
Date
From: Xie XiuQi <xiexiuqi@huawei.com>

ARM's v8.2 Extentions add support for Reliability, Availability and
Serviceability (RAS). On CPUs with these extensions system software
can use additional barriers to isolate errors and determine if faults
are pending.

Add cpufeature detection and a barrier in the context-switch code.
There is no need to use alternatives for this as CPUs that don't
support this feature will treat the instruction as a nop.

Platform level RAS support may require additional firmware support.

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
[Rebased, added esb and config option, reworded commit message]
Signed-off-by: James Morse <james.morse@arm.com>
---
arch/arm64/Kconfig | 16 ++++++++++++++++
arch/arm64/include/asm/barrier.h | 1 +
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/include/asm/sysreg.h | 2 ++
arch/arm64/kernel/cpufeature.c | 13 +++++++++++++
arch/arm64/kernel/process.c | 3 +++
6 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index dfd908630631..4d87aa963d83 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -960,6 +960,22 @@ config ARM64_UAO
regular load/store instructions if the cpu does not implement the
feature.

+config ARM64_RAS_EXTN
+ bool "Enable support for RAS CPU Extensions"
+ default y
+ help
+ CPUs that support the Reliability, Availability and Serviceability
+ (RAS) Extensions, part of ARMv8.2 are able to track faults and
+ errors, classify them and report them to software.
+
+ On CPUs with these extensions system software can use additional
+ barriers to determine if faults are pending and read the
+ classification from a new set of registers.
+
+ Selecting this feature will allow the kernel to use these barriers
+ and access the new registers if the system supports the extension.
+ Platform RAS features may additionally depend on firmware support.
+
endmenu

config ARM64_MODULE_CMODEL_LARGE
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 0fe7e43b7fbc..8b0a0eb67625 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -30,6 +30,7 @@
#define isb() asm volatile("isb" : : : "memory")
#define dmb(opt) asm volatile("dmb " #opt : : : "memory")
#define dsb(opt) asm volatile("dsb " #opt : : : "memory")
+#define esb() asm volatile("hint #16" : : : "memory")

#define mb() dsb(sy)
#define rmb() dsb(ld)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 8d2272c6822c..f93bf77f1f74 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -39,7 +39,8 @@
#define ARM64_WORKAROUND_QCOM_FALKOR_E1003 18
#define ARM64_WORKAROUND_858921 19
#define ARM64_WORKAROUND_CAVIUM_30115 20
+#define ARM64_HAS_RAS_EXTN 21

-#define ARM64_NCAPS 21
+#define ARM64_NCAPS 22

#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 248339e4aaf5..35b786b43ee4 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -331,6 +331,7 @@
#define ID_AA64ISAR1_JSCVT_SHIFT 12

/* id_aa64pfr0 */
+#define ID_AA64PFR0_RAS_SHIFT 28
#define ID_AA64PFR0_GIC_SHIFT 24
#define ID_AA64PFR0_ASIMD_SHIFT 20
#define ID_AA64PFR0_FP_SHIFT 16
@@ -339,6 +340,7 @@
#define ID_AA64PFR0_EL1_SHIFT 4
#define ID_AA64PFR0_EL0_SHIFT 0

+#define ID_AA64PFR0_RAS_V1 0x1
#define ID_AA64PFR0_FP_NI 0xf
#define ID_AA64PFR0_FP_SUPPORTED 0x0
#define ID_AA64PFR0_ASIMD_NI 0xf
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9f9e0064c8c1..a807ab55ee10 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -124,6 +124,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
};

static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64PFR0_RAS_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64PFR0_GIC_SHIFT, 4, 0),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT, 4, ID_AA64PFR0_ASIMD_NI),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_FP_SHIFT, 4, ID_AA64PFR0_FP_NI),
@@ -888,6 +889,18 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.min_field_value = 0,
.matches = has_no_fpsimd,
},
+#ifdef CONFIG_ARM64_RAS_EXTN
+ {
+ .desc = "RAS Extension Support",
+ .capability = ARM64_HAS_RAS_EXTN,
+ .def_scope = SCOPE_SYSTEM,
+ .matches = has_cpuid_feature,
+ .sys_reg = SYS_ID_AA64PFR0_EL1,
+ .sign = FTR_UNSIGNED,
+ .field_pos = ID_AA64PFR0_RAS_SHIFT,
+ .min_field_value = ID_AA64PFR0_RAS_V1,
+ },
+#endif /* CONFIG_ARM64_RAS_EXTN */
{},
};

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index c845c8c04d95..7a17b4a1bd9e 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -370,6 +370,9 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
*/
dsb(ish);

+ /* Deliver any pending SError from prev */
+ esb();
+
/* the actual thread switch */
last = cpu_switch_to(prev, next);

--
2.14.1
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