[PATCH v6 03/13] arm64: cpufeature: Detect CPU RAS Extentions

[James Morse]

From: Xie XiuQi <xiexiuqi at 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.

Platform level RAS support may require additional firmware support.

Signed-off-by: Xie XiuQi <xiexiuqi at huawei.com>
[Rebased added config option, reworded commit message]
Signed-off-by: James Morse <james.morse at arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>
---
Changes since v4:
 * Removed barrier in context switch

 arch/arm64/Kconfig               | 16 ++++++++++++++++
 arch/arm64/include/asm/cpucaps.h |  3 ++-
 arch/arm64/include/asm/sysreg.h  |  2 ++
 arch/arm64/kernel/cpufeature.c   | 13 +++++++++++++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 664fadc2aa2e..1d51c8edf34b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1062,6 +1062,22 @@ config ARM64_PMEM
 	  operations if DC CVAP is not supported (following the behaviour of
 	  DC CVAP itself if the system does not define a point of persistence).
 
+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_SVE
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 7049b4802587..bb263820de13 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -44,7 +44,8 @@
 #define ARM64_UNMAP_KERNEL_AT_EL0		23
 #define ARM64_HARDEN_BRANCH_PREDICTOR		24
 #define ARM64_HARDEN_BP_POST_GUEST_EXIT		25
+#define ARM64_HAS_RAS_EXTN			26
 
-#define ARM64_NCAPS				26
+#define ARM64_NCAPS				27
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 1a8108f84932..321622e9f9c3 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -498,6 +498,7 @@
 #define ID_AA64PFR0_CSV3_SHIFT		60
 #define ID_AA64PFR0_CSV2_SHIFT		56
 #define ID_AA64PFR0_SVE_SHIFT		32
+#define ID_AA64PFR0_RAS_SHIFT		28
 #define ID_AA64PFR0_GIC_SHIFT		24
 #define ID_AA64PFR0_ASIMD_SHIFT		20
 #define ID_AA64PFR0_FP_SHIFT		16
@@ -507,6 +508,7 @@
 #define ID_AA64PFR0_EL0_SHIFT		0
 
 #define ID_AA64PFR0_SVE			0x1
+#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 d88cd0e88606..0c0af18121e1 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -149,6 +149,7 @@ 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_SVE_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_RAS_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 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),
@@ -1028,6 +1029,18 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.enable = sve_kernel_enable,
 	},
 #endif /* CONFIG_ARM64_SVE */
+#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 */
 	{},
 };
 
-- 
2.15.1