linux-kernel - [tip:x86/asm] x86/asm/tsc, x86/cpu/amd: Use the full 64-bit TSC to detect the 2.6.2 bug

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Message-ID: <tip-3796366614598e48edf0561b86f18c230a7debc8@git.kernel.org>
Date:	Mon, 6 Jul 2015 08:41:48 -0700
From:	tip-bot for Andy Lutomirski <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, ralf@...ux-mips.org, luto@...capital.net,
	mingo@...nel.org, brgerst@...il.com, linux-kernel@...r.kernel.org,
	luto@...nel.org, tglx@...utronix.de, bp@...e.de,
	kvm@...r.kernel.org, ray.huang@....com, lenb@...nel.org,
	dvlasenk@...hat.com, torvalds@...ux-foundation.org,
	peterz@...radead.org, bp@...en8.de, john.stultz@...aro.org
Subject: [tip:x86/asm] x86/asm/tsc, x86/cpu/amd:
  Use the full 64-bit TSC to detect the 2.6.2 bug

Commit-ID:  3796366614598e48edf0561b86f18c230a7debc8
Gitweb:     http://git.kernel.org/tip/3796366614598e48edf0561b86f18c230a7debc8
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Thu, 25 Jun 2015 18:44:01 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 6 Jul 2015 15:23:27 +0200

x86/asm/tsc, x86/cpu/amd: Use the full 64-bit TSC to detect the 2.6.2 bug

This code is timing 100k indirect calls, so the added overhead
of counting the number of cycles elapsed as a 64-bit number
should be insignificant.  Drop the optimization of using a
32-bit count.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Huang Rui <ray.huang@....com>
Cc: John Stultz <john.stultz@...aro.org>
Cc: Len Brown <lenb@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: kvm ML <kvm@...r.kernel.org>
Link: http://lkml.kernel.org/r/d58f339a9c0dd8352b50d2f7a216f67ec2844f20.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/amd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index dd3a4ba..a69710d 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -114,7 +114,7 @@ static void init_amd_k6(struct cpuinfo_x86 *c)
 		const int K6_BUG_LOOP = 1000000;
 		int n;
 		void (*f_vide)(void);
-		unsigned long d, d2;
+		u64 d, d2;
 
 		printk(KERN_INFO "AMD K6 stepping B detected - ");
 
@@ -125,10 +125,10 @@ static void init_amd_k6(struct cpuinfo_x86 *c)
 
 		n = K6_BUG_LOOP;
 		f_vide = vide;
-		rdtscl(d);
+		d = native_read_tsc();
 		while (n--)
 			f_vide();
-		rdtscl(d2);
+		d2 = native_read_tsc();
 		d = d2-d;
 
 		if (d > 20*K6_BUG_LOOP)
--
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