arm64: alternatives: add cpu feature for lse atomics

Add a CPU feature for the LSE atomic instructions, so that they can be
patched in at runtime when we detect that they are supported.

Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/cpufeature.h

@@ -26,8 +26,9 @@
 #define ARM64_WORKAROUND_845719			2
 #define ARM64_HAS_SYSREG_GIC_CPUIF		3
 #define ARM64_HAS_PAN				4
+#define ARM64_CPU_FEAT_LSE_ATOMICS		5
 
-#define ARM64_NCAPS				5
+#define ARM64_NCAPS				6
 
 #ifndef __ASSEMBLY__
 

arch/arm64/kernel/setup.c

@@ -284,6 +284,7 @@ static void __init setup_processor(void)
 		default:
 		case 2:
 			elf_hwcap |= HWCAP_ATOMICS;
+			cpus_set_cap(ARM64_CPU_FEAT_LSE_ATOMICS);
 		case 1:
 			/* RESERVED */
 		case 0: