From: Borislav Petkov bp@suse.de
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@suse.de Cc: Joerg Roedel joro@8bytes.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/1455578358-28347-1-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar mingo@kernel.org 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 ---
arch/x86/include/asm/cpufeature.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 1c9d6c5..03ca602 100644 --- 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[NBUGINTS*32]; * 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)