linux-kernel - [PATCH v8 03/10] x86, mpx: add macro cpu_has

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Message-Id: <1410425210-24789-4-git-send-email-qiaowei.ren@intel.com>
Date:	Thu, 11 Sep 2014 16:46:43 +0800
From:	Qiaowei Ren <qiaowei.ren@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>
Cc:	x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Qiaowei Ren <qiaowei.ren@...el.com>
Subject: [PATCH v8 03/10] x86, mpx: add macro cpu_has_mpx

In order to do performance optimization, this patch adds macro
cpu_has_mpx which will directly return 0 when MPX is not supported
by kernel.

Community gave a lot of comments on this macro cpu_has_mpx in previous
version. Dave will introduce a patchset about disabled features to fix
it later.

In this code:
        if (cpu_has_mpx)
                do_some_mpx_thing();

The patch series from Dave will introduce a new macro cpu_feature_enabled()
(if merged after this patchset) to replace the cpu_has_mpx.
        if (cpu_feature_enabled(X86_FEATURE_MPX))
                do_some_mpx_thing();

Signed-off-by: Qiaowei Ren <qiaowei.ren@...el.com>
---
 arch/x86/include/asm/cpufeature.h |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index bb9b258..82ec7ed 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -353,6 +353,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 #define cpu_has_eager_fpu	boot_cpu_has(X86_FEATURE_EAGER_FPU)
 #define cpu_has_topoext		boot_cpu_has(X86_FEATURE_TOPOEXT)
 
+#ifdef CONFIG_X86_INTEL_MPX
+#define cpu_has_mpx boot_cpu_has(X86_FEATURE_MPX)
+#else
+#define cpu_has_mpx 0
+#endif /* CONFIG_X86_INTEL_MPX */
+
 #ifdef CONFIG_X86_64
 
 #undef  cpu_has_vme
-- 
1.7.1

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