From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: why guests show "Clocksource tsc unstable" on bootup? Date: Sun, 15 Mar 2009 15:20:38 +0200 Message-ID: <49BD00A6.20400@redhat.com> References: <49B5050B.9050204@wpkg.org> <49BCFB0D.2000901@redhat.com> <49BCFD43.9010604@wpkg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "kvm@vger.kernel.org" To: Tomasz Chmielewski Return-path: Received: from mx2.redhat.com ([66.187.237.31]:48552 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754014AbZCONUl (ORCPT ); Sun, 15 Mar 2009 09:20:41 -0400 In-Reply-To: <49BCFD43.9010604@wpkg.org> Sender: kvm-owner@vger.kernel.org List-ID: Tomasz Chmielewski wrote: > 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? > Good question. I don't know what the answer is. Maybe the scheduler uses tsc for its internal clock. > > 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 > This cpu indeed has unstable tsc, but disabling cpufreq should have fixed it. Maybe we need to disable C-states as well? -- error compiling committee.c: too many arguments to function