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

tip-bot for Andy Lutomirski
2015-07-06T15:43:02Z

Commit-ID: 3796366614598e48edf0561b86f18c230a7debc8
Gitweb: http://git.kernel.org/tip/3796366614598e48edf0561b86f18c230a7debc8
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Thu, 25 Jun 2015 18:44:01 +0200
Committer: Ingo Molnar <mingo@kernel.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@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/d58f339a9c0dd8352b50d2f7a216f67ec2844f20.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.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)