Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 29/43] x86/cpufeature: Speed up cpu_feature_enabled() | Date | Mon, 16 Jul 2018 09:36:34 +0200 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> ---
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)
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