Re: why guests show "Clocksource tsc unstable" on bootup?

[Tomasz Chmielewski <mangoo@wpkg.org>]

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