linux-kernel - [PATCH 2/4] arm64: cpufeature: add feature for CRC32 instructions

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Date:   Mon, 27 Aug 2018 13:02:43 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     linux-arm-kernel@...ts.infradead.org, linux-crypto@...r.kernel.org
Cc:     will.deacon@....com, catalin.marinas@....com,
        herbert@...dor.apana.org.au, ebiggers@...gle.com,
        suzuki.poulose@....com, linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH 2/4] arm64: cpufeature: add feature for CRC32 instructions

Add a CRC32 feature bit and wire it up to the CPU id register so we
will be able to use alternatives patching for CRC32 operations.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 arch/arm64/include/asm/cpucaps.h | 3 ++-
 arch/arm64/kernel/cpufeature.c   | 9 +++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index ae1f70450fb2..9932aca9704b 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -51,7 +51,8 @@
 #define ARM64_SSBD				30
 #define ARM64_MISMATCHED_CACHE_TYPE		31
 #define ARM64_HAS_STAGE2_FWB			32
+#define ARM64_HAS_CRC32				33
 
-#define ARM64_NCAPS				33
+#define ARM64_NCAPS				34
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index e238b7932096..7626b80128f5 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1222,6 +1222,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.cpu_enable = cpu_enable_hw_dbm,
 	},
 #endif
+	{
+		.desc = "CRC32 instructions",
+		.capability = ARM64_HAS_CRC32,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_cpuid_feature,
+		.sys_reg = SYS_ID_AA64ISAR0_EL1,
+		.field_pos = ID_AA64ISAR0_CRC32_SHIFT,
+		.min_field_value = 1,
+	},
 	{},
 };
 
-- 
2.18.0