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>
diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index 08b4c06..37f5516 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -112,6 +112,7 @@
#define MMU_FTRS_PA6T MMU_FTRS_DEFAULT_HPTE_ARCH_V2 | \
MMU_FTR_CI_LARGE_PAGE | MMU_FTR_NO_SLBIE_B
#ifndef __ASSEMBLY__
+#include <linux/bug.h>
#include <asm/cputable.h>
#ifdef CONFIG_PPC_FSL_BOOK3E