linux-kernel - [PATCH 3/3] x86/cpu: Add CLZERO detection

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Message-Id: <1446207099-24948-4-git-send-email-bp@alien8.de>
Date:	Fri, 30 Oct 2015 13:11:39 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 3/3] x86/cpu: Add CLZERO detection

From: Wan Zongshun <Vincent.Wan@....com>

AMD Fam17h processors introduce support for the CLZERO instruction. It
zeroes out the 64 byte cache line specified in RAX.

Add the bit here to allow /proc/cpuinfo to list the feature.

Boris: we're adding this as a separate ->x86_capability leaf because
CPUID_80000008_EBX is going to contain more feature bits and it will
fill out with time.

Signed-off-by: Wan Zongshun <Vincent.Wan@....com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Huang Rui <ray.huang@....com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Tony Luck <tony.luck@...el.com>
Cc: x86-ml <x86@...nel.org>
Link: http://lkml.kernel.org/r/1446059010-28010-3-git-send-email-Aravind.Gopalakrishnan@amd.com
[Wrap code in patch form, fix comments. ]
Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/include/asm/cpufeature.h | 5 ++++-
 arch/x86/kernel/cpu/common.c      | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 9727b3b48bd1..e4f8010f22e0 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -12,7 +12,7 @@
 #include <asm/disabled-features.h>
 #endif
 
-#define NCAPINTS	13	/* N 32-bit words worth of info */
+#define NCAPINTS	14	/* N 32-bit words worth of info */
 #define NBUGINTS	1	/* N 32-bit bug flags */
 
 /*
@@ -255,6 +255,9 @@
 /* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:1 (edx), word 12 */
 #define X86_FEATURE_CQM_OCCUP_LLC (12*32+ 0) /* LLC occupancy monitoring if 1 */
 
+/* AMD-defined CPU features, CPUID level 0x80000008 (ebx), word 13 */
+#define X86_FEATURE_CLZERO	(13*32+0) /* CLZERO instruction */
+
 /*
  * BUG word(s)
  */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index de22ea7ff82f..4ddd780aeac9 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -670,6 +670,7 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 
 		c->x86_virt_bits = (eax >> 8) & 0xff;
 		c->x86_phys_bits = eax & 0xff;
+		c->x86_capability[13] = cpuid_ebx(0x80000008);
 	}
 #ifdef CONFIG_X86_32
 	else if (cpu_has(c, X86_FEATURE_PAE) || cpu_has(c, X86_FEATURE_PSE36))
-- 
2.3.5

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