From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: why guests show "Clocksource tsc unstable" on bootup? Date: Sun, 15 Mar 2009 14:06:11 +0100 Message-ID: <49BCFD43.9010604@wpkg.org> References: <49B5050B.9050204@wpkg.org> <49BCFB0D.2000901@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "kvm@vger.kernel.org" To: Avi Kivity Return-path: Received: from mx03.syneticon.net ([78.111.66.105]:49375 "EHLO mx03.syneticon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750716AbZCONGR (ORCPT ); Sun, 15 Mar 2009 09:06:17 -0400 In-Reply-To: <49BCFB0D.2000901@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity schrieb: > Tomasz Chmielewski wrote: >> Why do my guests show "Clocksource tsc unstable" on bootup? >> > > Linux expects the tsc to be monotonic and to have a 1:1 correspondence > with real time, which isn't easy to achieve with virtualization. But the clocksource is kvm-clock, so why does the guest probe tsc at all? >> dmesg shows that kvm-clock was set as the primary cpu clock. >> Yet a bit later kernel says "Clocksource tsc unstable". >> >> Is it something to worry about, or perhaps calculating tsc is hardcoded? >> And as such, will be always checked? >> Or, is it host CPU related? >> >> [ 0.000000] kvm-clock: cpu 0, msr 0:3baf81, boot clock >> [ 0.000000] kvm-clock: cpu 0, msr 0:1208f81, primary cpu clock >> [ 0.000000] Kernel command line: root=/dev/vda1 ro quiet >> clocksource=kvm-clock >> [ 1.253602] rtc_cmos 00:01: setting system clock to 2009-03-09 >> 11:41:30 UTC (1236598890) >> [ 41.500623] Clocksource tsc unstable (delta = -153498948 ns) >> >> > > What host cpu and kvm version are you using? I pasted a part of /proc/cpuinfo below. I saw these with kvm-83 and kvm-84 (with cpufreq disabled, as it perhaps can matter). processor : 3 vendor_id : AuthenticAMD cpu family : 15 model : 65 model name : Dual-Core AMD Opteron(tm) Processor 2212 stepping : 2 cpu MHz : 2000.000 cache size : 1024 KB physical id : 1 siblings : 2 core id : 1 cpu cores : 2 fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow rep_good pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy bogomips : 3993.03 TLB size : 1024 4K pages clflush size : 64 cache_alignment : 64 address sizes : 40 bits physical, 48 bits virtual power management: ts fid vid ttp tm stc -- Tomasz Chmielewski http://wpkg.org