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x86/cpu: Provide a config option to disable static_cpu_has

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commit 6e1315fe82308cd29e7550eab967262e8bbc71a3 upstream

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.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Link: http://lkml.kernel.org/r/1449481182-27541-5-git-send-email-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Matt Helsley (VMware) <matt.helsley@gmail.com>
Reviewed-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Bo Gan <ganb@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Borislav Petkov 2018-07-14 02:26:17 -07:00 committed by Greg Kroah-Hartman
parent 0f66fae5d6
commit 8c9814143e
2 changed files with 12 additions and 1 deletions
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11
arch/x86/Kconfig
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@ -346,6 +346,17 @@ 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)

2
arch/x86/include/asm/cpufeature.h
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@ -422,7 +422,7 @@ 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);