forked from luck/tmp_suning_uos_patched
powerpc: Add option to use jump label for cpu_has_feature()
We do binary patching of asm code using CPU features, which is a one-time operation, done during early boot. However checks of CPU features in C code are currently done at run time, even though the set of CPU features can never change after boot. We can optimise this by using jump labels to implement cpu_has_feature(), meaning checks in C code are binary patched into a single nop or branch. For a C sequence along the lines of: if (cpu_has_feature(FOO)) return 2; The generated code before is roughly: ld r9,-27640(r2) ld r9,0(r9) lwz r9,32(r9) cmpwi cr7,r9,0 bge cr7, 1f li r3,2 blr 1: ... After (true): nop li r3,2 blr After (false): b 1f li r3,2 blr 1: ... mpe: Rename MAX_CPU_FEATURES as we already have a #define with that name, and define it simply as a constant, rather than doing tricks with sizeof and NULL pointers. Rename the array to cpu_feature_keys. Use the kconfig we added to guard it. Add BUILD_BUG_ON() if the feature is not a compile time constant. Rewrite the change log. 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>
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@ -11,10 +11,34 @@ static inline bool early_cpu_has_feature(unsigned long feature)
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(CPU_FTRS_POSSIBLE & cur_cpu_spec->cpu_features & feature));
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}
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#ifdef CONFIG_JUMP_LABEL_FEATURE_CHECKS
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#include <linux/jump_label.h>
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#define NUM_CPU_FTR_KEYS 64
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extern struct static_key_true cpu_feature_keys[NUM_CPU_FTR_KEYS];
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static __always_inline bool cpu_has_feature(unsigned long feature)
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{
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int i;
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BUILD_BUG_ON(!__builtin_constant_p(feature));
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if (CPU_FTRS_ALWAYS & feature)
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return true;
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if (!(CPU_FTRS_POSSIBLE & feature))
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return false;
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i = __builtin_ctzl(feature);
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return static_branch_likely(&cpu_feature_keys[i]);
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}
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#else
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static inline bool cpu_has_feature(unsigned long feature)
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{
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return early_cpu_has_feature(feature);
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}
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#endif
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_POWERPC_CPUFEATURE_H */
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@ -123,6 +123,12 @@ extern void do_feature_fixups(unsigned long value, void *fixup_start,
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extern const char *powerpc_base_platform;
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#ifdef CONFIG_JUMP_LABEL_FEATURE_CHECKS
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extern void cpu_feature_keys_init(void);
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#else
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static inline void cpu_feature_keys_init(void) { }
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#endif
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/* TLB flush actions. Used as argument to cpu_spec.flush_tlb() hook */
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enum {
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TLB_INVAL_SCOPE_GLOBAL = 0, /* invalidate all TLBs */
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@ -112,6 +112,7 @@
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#define MMU_FTRS_PA6T MMU_FTRS_DEFAULT_HPTE_ARCH_V2 | \
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MMU_FTR_CI_LARGE_PAGE | MMU_FTR_NO_SLBIE_B
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#ifndef __ASSEMBLY__
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#include <linux/bug.h>
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#include <asm/cputable.h>
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#ifdef CONFIG_PPC_FSL_BOOK3E
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@ -15,6 +15,7 @@
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#include <linux/threads.h>
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#include <linux/init.h>
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#include <linux/export.h>
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#include <linux/jump_label.h>
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#include <asm/oprofile_impl.h>
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#include <asm/cputable.h>
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@ -2224,3 +2225,22 @@ struct cpu_spec * __init identify_cpu(unsigned long offset, unsigned int pvr)
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return NULL;
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}
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#ifdef CONFIG_JUMP_LABEL_FEATURE_CHECKS
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struct static_key_true cpu_feature_keys[NUM_CPU_FTR_KEYS] = {
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[0 ... NUM_CPU_FTR_KEYS - 1] = STATIC_KEY_TRUE_INIT
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};
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EXPORT_SYMBOL_GPL(cpu_feature_keys);
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void __init cpu_feature_keys_init(void)
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{
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int i;
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for (i = 0; i < NUM_CPU_FTR_KEYS; i++) {
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unsigned long f = 1ul << i;
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if (!(cur_cpu_spec->cpu_features & f))
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static_branch_disable(&cpu_feature_keys[i]);
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}
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}
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#endif
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@ -195,6 +195,7 @@ void __init apply_feature_fixups(void)
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* CPU/MMU features.
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*/
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jump_label_init();
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cpu_feature_keys_init();
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}
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static int __init check_features(void)
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