powerpc: Add option to use jump label for mmu_has_feature()

As we just did for CPU features.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/cpu_has_feature.h

@@ -3,6 +3,7 @@
 
 #ifndef __ASSEMBLY__
 
+#include <linux/bug.h>
 #include <asm/cputable.h>
 
 static inline bool early_cpu_has_feature(unsigned long feature)

arch/powerpc/include/asm/mmu.h

@@ -141,6 +141,43 @@ static inline bool early_mmu_has_feature(unsigned long feature)
 	return !!(MMU_FTRS_POSSIBLE & cur_cpu_spec->mmu_features & feature);
 }
 
+#ifdef CONFIG_JUMP_LABEL_FEATURE_CHECKS
+#include <linux/jump_label.h>
+
+#define NUM_MMU_FTR_KEYS	32
+
+extern struct static_key_true mmu_feature_keys[NUM_MMU_FTR_KEYS];
+
+extern void mmu_feature_keys_init(void);
+
+static __always_inline bool mmu_has_feature(unsigned long feature)
+{
+	int i;
+
+	BUILD_BUG_ON(!__builtin_constant_p(feature));
+
+	if (!(MMU_FTRS_POSSIBLE & feature))
+		return false;
+
+	i = __builtin_ctzl(feature);
+	return static_branch_likely(&mmu_feature_keys[i]);
+}
+
+static inline void mmu_clear_feature(unsigned long feature)
+{
+	int i;
+
+	i = __builtin_ctzl(feature);
+	cur_cpu_spec->mmu_features &= ~feature;
+	static_branch_disable(&mmu_feature_keys[i]);
+}
+#else
+
+static inline void mmu_feature_keys_init(void)
+{
+
+}
+
 static inline bool mmu_has_feature(unsigned long feature)
 {
 	return early_mmu_has_feature(feature);
@@ -150,6 +187,7 @@ static inline void mmu_clear_feature(unsigned long feature)
 {
 	cur_cpu_spec->mmu_features &= ~feature;
 }
+#endif /* CONFIG_JUMP_LABEL */
 
 extern unsigned int __start___mmu_ftr_fixup, __stop___mmu_ftr_fixup;
 

arch/powerpc/kernel/cputable.c

@@ -2243,4 +2243,21 @@ void __init cpu_feature_keys_init(void)
 			static_branch_disable(&cpu_feature_keys[i]);
 	}
 }
+
+struct static_key_true mmu_feature_keys[NUM_MMU_FTR_KEYS] = {
+			[0 ... NUM_MMU_FTR_KEYS - 1] = STATIC_KEY_TRUE_INIT
+};
+EXPORT_SYMBOL_GPL(mmu_feature_keys);
+
+void __init mmu_feature_keys_init(void)
+{
+	int i;
+
+	for (i = 0; i < NUM_MMU_FTR_KEYS; i++) {
+		unsigned long f = 1ul << i;
+
+		if (!(cur_cpu_spec->mmu_features & f))
+			static_branch_disable(&mmu_feature_keys[i]);
+	}
+}
 #endif

arch/powerpc/lib/feature-fixups.c

@@ -196,6 +196,7 @@ void __init apply_feature_fixups(void)
 	 */
 	jump_label_init();
 	cpu_feature_keys_init();
+	mmu_feature_keys_init();
 }
 
 static int __init check_features(void)