[PATCH 4.4 29/43] x86/cpufeature: Speed up cpu_feature_enabled()
From: Greg Kroah-Hartman
Date: Mon Jul 16 2018 - 03:44:56 EST
4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Borislav Petkov <bp@xxxxxxx>
commit f2cc8e0791c70833758101d9756609a08dd601ec upstream
When GCC cannot do constant folding for this macro, it falls back to
cpu_has(). But static_cpu_has() is optimal and it works at all times
now. So use it and speedup the fallback case.
Before we had this:
mov 0x99d674(%rip),%rdx # ffffffff81b0d9f4 <boot_cpu_data+0x34>
shr $0x2e,%rdx
and $0x1,%edx
jne ffffffff811704e9 <do_munmap+0x3f9>
After alternatives patching, it turns into:
jmp 0xffffffff81170390
nopl (%rax)
...
callq ffffffff81056e00 <mpx_notify_unmap>
ffffffff81170390: mov 0x170(%r12),%rdi
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1455578358-28347-1-git-send-email-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Srivatsa S. Bhat <srivatsa@xxxxxxxxxxxxx>
Reviewed-by: Matt Helsley (VMware) <matt.helsley@xxxxxxxxx>
Reviewed-by: Alexey Makhalov <amakhalov@xxxxxxxxxx>
Reviewed-by: Bo Gan <ganb@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/cpufeature.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -88,8 +88,7 @@ extern const char * const x86_bug_flags[
* is not relevant.
*/
#define cpu_feature_enabled(bit) \
- (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : \
- cpu_has(&boot_cpu_data, bit))
+ (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : static_cpu_has(bit))
#define boot_cpu_has(bit) cpu_has(&boot_cpu_data, bit)