@@ -121,10 +121,29 @@
DECLARE_PER_CPU(int, next_tlbcam_idx);
#endif
+#ifdef CONFIG_JUMP_LABEL
+#include <linux/jump_label_base.h>
+
+#define MAX_MMU_FEATURES 32
+
+extern struct static_key mmu_feat_keys[MAX_MMU_FEATURES];
+extern struct static_key mmu_feat_keys_enabled;
+
+static inline int mmu_has_feature(unsigned long feature)
+{
+ if (static_key_false(&mmu_feat_keys_enabled)) {
+ int i = __builtin_ctzl(feature);
+
+ return static_key_false(&mmu_feat_keys[i]);
+ } else
+ return !!(cur_cpu_spec->mmu_features & feature);
+}
+#else
static inline int mmu_has_feature(unsigned long feature)
{
return (cur_cpu_spec->mmu_features & feature);
}
+#endif
static inline void mmu_clear_feature(unsigned long feature)
{
@@ -2280,4 +2280,24 @@ static __init int cpu_feat_keys_init(void)
return 0;
}
early_initcall(cpu_feat_keys_init);
+
+struct static_key mmu_feat_keys[MAX_MMU_FEATURES];
+struct static_key mmu_feat_keys_enabled;
+
+static __init int mmu_feat_keys_init(void)
+{
+ int i;
+
+ for (i = 0; i < MAX_MMU_FEATURES; i++) {
+ unsigned long f = 1 << i;
+
+ if (cur_cpu_spec->mmu_features & f)
+ static_key_slow_inc(&mmu_feat_keys[i]);
+ }
+
+ static_key_slow_inc(&mmu_feat_keys_enabled);
+
+ return 0;
+}
+early_initcall(mmu_feat_keys_init);
#endif
The mmu features are fixed once the probe of mmu features are done. And the function mmu_has_feature() does be used in some hot path. The checking of the mmu features for each time of invoking of mmu_has_feature() seems suboptimal. This tries to reduce this overhead of this check by using jump label. But we can only use the jump label for this check only after the execution of jump_label_init(), so we introduce another jump label to still do the feature check by default before all the mmu feature jump labels are initialized. Signed-off-by: Kevin Hao <haokexin@gmail.com> --- arch/powerpc/include/asm/mmu.h | 19 +++++++++++++++++++ arch/powerpc/kernel/cputable.c | 20 ++++++++++++++++++++ 2 files changed, 39 insertions(+)