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

[Avi Kivity <avi@redhat.com>]

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.

> 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?


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