From 8652cb4b0d87accbe78725fd2a13be2787059649 Mon Sep 17 00:00:00 2001 From: Prarit Bhargava Date: Wed, 12 Nov 2008 13:35:00 -0500 Subject: [PATCH] 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 Signed-off-by: Ingo Molnar --- arch/x86/kernel/time_64.c | 2 ++ 1 file changed, 2 insertions(+) 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); -- 2.20.1