From: Borislav Petkov <b...@suse.de>
This brings .text savings of about ~1.6K when building a tinyconfig. It
is off by default so nothing changes for the default.
Kconfig help text from Josh.
Reviewed-by: Josh Triplett <j...@joshtriplett.org>
Signed-off-by: Borislav Petkov <b...@suse.de>
---
arch/x86/Kconfig | 11 +++++++++++
arch/x86/include/asm/cpufeature.h | 2 +-
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index db3622f22b61..a2abc2fb6970 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -349,6 +349,17 @@ config X86_FEATURE_NAMES
If in doubt, say Y.
+config X86_FAST_FEATURE_TESTS
+ bool "Fast CPU feature tests" if EMBEDDED
+ default y
+ ---help---
+ Some fast-paths in the kernel depend on the capabilities of the CPU.
+ Say Y here for the kernel to patch in the appropriate code at runtime
+ based on the capabilities of the CPU. The infrastructure for patching
+ code at runtime takes up some additional space; space-constrained
+ embedded systems may wish to say N here to produce smaller, slightly
+ slower code.
+
config X86_X2APIC
bool "Support x2apic"
depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index 144b042c0872..43e144474043 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -409,7 +409,7 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
* fast paths and boot_cpu_has() otherwise!
*/
-#if __GNUC__ >= 4
+#if __GNUC__ >= 4 && defined(CONFIG_X86_FAST_FEATURE_TESTS)
extern void warn_pre_alternatives(void);
extern bool __static_cpu_has_safe(u16 bit);
--
2.3.5
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