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 cb19d65..418a095 100644
--- a/arch/x86/kernel/time_64.c
+++ b/arch/x86/kernel/time_64.c
@@ -80,6 +80,8 @@
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);