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

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Message-ID: <tip-2167ceabf34163727ca4e283c0f030e3960932e5@git.kernel.org>
Date:	Sun, 1 Nov 2015 02:28:30 -0800
From:	tip-bot for Wan Zongshun <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, mingo@...nel.org, tony.luck@...el.com, bp@...e.de,
	Vincent.Wan@....com, ray.huang@....com, dvlasenk@...hat.com,
	bp@...en8.de, tglx@...utronix.de, aravind.gopalakrishnan@....com,
	peterz@...radead.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, luto@...nel.org
Subject: [tip:x86/cpu] x86/cpu: Add CLZERO detection

Commit-ID:  2167ceabf34163727ca4e283c0f030e3960932e5
Gitweb:     http://git.kernel.org/tip/2167ceabf34163727ca4e283c0f030e3960932e5
Author:     Wan Zongshun <Vincent.Wan@....com>
AuthorDate: Fri, 30 Oct 2015 13:11:39 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 1 Nov 2015 11:26:23 +0100

x86/cpu: Add CLZERO detection

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>
Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
[ Wrap code in patch form, fix comments. ]
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Huang Rui <ray.huang@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Tony Luck <tony.luck@...el.com>
Link: http://lkml.kernel.org/r/1446207099-24948-4-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 9727b3b..e4f8010 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 de22ea7..4ddd780 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))
--
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