From: Prarit Bhargava <prarit@redhat.com>
Date: Wed, 12 Nov 2008 18:35:00 +0000 (-0500)
Subject: x86: warn of incorrect cpu_khz on AMD systems
X-Git-Tag: v2.6.29-rc1~587^2~4^6~8
X-Git-Url: http://bbs.cooldavid.org/git/?a=commitdiff_plain;h=8652cb4b0d87accbe78725fd2a13be2787059649;p=net-next-2.6.git

x86: warn of incorrect cpu_khz on AMD systems

Impact: add debug check

If none of the perfctrs are free when calculating cpu_khz we default to
using ctr 3 (ie, we just choose 3).  This may lead to an incorrect tsc
freq value which can cause the system to be unstable.

To aid in future debugging, WARN the user of a potential problem.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/arch/x86/kernel/time_64.c b/arch/x86/kernel/time_64.c
index cb19d650c21..418a095c579 100644
--- a/arch/x86/kernel/time_64.c
+++ b/arch/x86/kernel/time_64.c
@@ -80,6 +80,8 @@ unsigned long __init calibrate_cpu(void)
 			break;
 	no_ctr_free = (i == 4);
 	if (no_ctr_free) {
+		WARN(1, KERN_WARNING "Warning: AMD perfctrs busy ... "
+		     "cpu_khz value may be incorrect.\n");
 		i = 3;
 		rdmsrl(MSR_K7_EVNTSEL3, evntsel3);
 		wrmsrl(MSR_K7_EVNTSEL3, 0);