[PATCH v3 19/21] powerpc: Add option to use jump label for mmu_has_feature()

[Michael Ellerman]

From: Kevin Hao <haoke...@gmail.com>

As we just did for CPU features.

Signed-off-by: Kevin Hao <haoke...@gmail.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
 arch/powerpc/include/asm/mmu.h    | 36 ++++++++++++++++++++++++++++++++++++
 arch/powerpc/kernel/cputable.c    | 17 +++++++++++++++++
 arch/powerpc/lib/feature-fixups.c |  1 +
 3 files changed, 54 insertions(+)

v3: Rename to mmu_feature_keys, and NUM_MMU_FTR_KEYS.
    Use the kconfig.

diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index e3eff365e55d..3900cb7fe7cf 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -140,6 +140,41 @@ static inline bool __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;
+
+       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 __mmu_has_feature(feature);
@@ -149,6 +184,7 @@ 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;
 
diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
index f268850f8fda..db14efc7d3e0 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/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
diff --git a/arch/powerpc/lib/feature-fixups.c 
b/arch/powerpc/lib/feature-fixups.c
index f90423faade0..8db370cec547 100644
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/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)
-- 
2.7.4

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