[PATCH v3 07/18] x86/cpu/amd: Use the full 64-bit TSC to detect the 2.6.2 bug

Andy Lutomirski
2015-06-17T00:41:20Z

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>
---
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 5bd3a99dc20b..c5ceec532799 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -107,7 +107,7 @@ 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 - ");

@@ -118,10 +118,10 @@ 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)
--
2.4.2