Merge branch 'swp' (early part) into for-next

arch/arm/kernel/setup.c

@@ -393,19 +393,34 @@ static void __init cpuid_init_hwcaps(void)
 		elf_hwcap |= HWCAP_LPAE;
 }
 
-static void __init feat_v6_fixup(void)
+static void __init elf_hwcap_fixup(void)
 {
-	int id = read_cpuid_id();
-
-	if ((id & 0xff0f0000) != 0x41070000)
-		return;
+	unsigned id = read_cpuid_id();
+	unsigned sync_prim;
 
 	/*
 	 * HWCAP_TLS is available only on 1136 r1p0 and later,
 	 * see also kuser_get_tls_init.
 	 */
-	if ((((id >> 4) & 0xfff) == 0xb36) && (((id >> 20) & 3) == 0))
+	if (read_cpuid_part() == ARM_CPU_PART_ARM1136 &&
+	    ((id >> 20) & 3) == 0) {
 		elf_hwcap &= ~HWCAP_TLS;
+		return;
+	}
+
+	/* Verify if CPUID scheme is implemented */
+	if ((id & 0x000f0000) != 0x000f0000)
+		return;
+
+	/*
+	 * If the CPU supports LDREX/STREX and LDREXB/STREXB,
+	 * avoid advertising SWP; it may not be atomic with
+	 * multiprocessing cores.
+	 */
+	sync_prim = ((read_cpuid_ext(CPUID_EXT_ISAR3) >> 8) & 0xf0) |
+		    ((read_cpuid_ext(CPUID_EXT_ISAR4) >> 20) & 0x0f);
+	if (sync_prim >= 0x13)
+		elf_hwcap &= ~HWCAP_SWP;
 }
 
 /*
@@ -609,7 +624,7 @@ static void __init setup_processor(void)
 #endif
 	erratum_a15_798181_init();
 
-	feat_v6_fixup();
+	elf_hwcap_fixup();
 
 	cacheid_init();
 	cpu_init();

arch/arm/kernel/swp_emulate.c

@@ -27,6 +27,7 @@
 #include <linux/perf_event.h>
 
 #include <asm/opcodes.h>
+#include <asm/system_info.h>
 #include <asm/traps.h>
 #include <asm/uaccess.h>
 
@@ -266,6 +267,9 @@ static struct undef_hook swp_hook = {
  */
 static int __init swp_emulation_init(void)
 {
+	if (cpu_architecture() < CPU_ARCH_ARMv7)
+		return 0;
+
 #ifdef CONFIG_PROC_FS
 	if (!proc_create("cpu/swp_emulation", S_IRUGO, NULL, &proc_status_fops))
 		return -ENOMEM;

arch/arm/mm/Kconfig

@@ -669,7 +669,7 @@ config ARM_VIRT_EXT
 	  details.
 
 config SWP_EMULATE
-	bool "Emulate SWP/SWPB instructions"
+	bool "Emulate SWP/SWPB instructions" if !SMP
 	depends on CPU_V7
 	default y if SMP
 	select HAVE_PROC_CPU if PROC_FS