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.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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 */

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,
+	},
 	{},
 };