From: Borislav Petkov <bp@alien8.de>
To: X86 ML <x86@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Joerg Roedel <joro@8bytes.org>
Subject: [PATCH] x86/cpufeature: Speedup cpu_feature_enabled()
Date: Tue, 16 Feb 2016 00:19:18 +0100 [thread overview]
Message-ID: <1455578358-28347-1-git-send-email-bp@alien8.de> (raw)
From: Borislav Petkov <bp@suse.de>
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>
---
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 9fba7a5dd24a..68e4e8258b84 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)
--
2.3.5
next reply other threads:[~2016-02-15 23:19 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-15 23:19 Borislav Petkov [this message]
2016-02-16 7:56 ` [tip:x86/asm] x86/cpufeature: Speed up cpu_feature_enabled() tip-bot for Borislav Petkov
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