Re: Houston, we have May 15, 1953 (says guest when host uses cpufreq, and dies)

Marcelo Tosatti
2009-02-18T18:46:55Z

On Wed, Feb 18, 2009 at 03:51:22PM +0100, Tomasz Chmielewski wrote:
> Is using cpufreq (i.e. with ondemand governor) on KVM host safe for guests?
>
> I enabled cpufreq on the host, it scaled down the host CPU (Dual-Core
> AMD Opteron(tm) Processor 2212) to 1 GHz from 2 GHz.
>
> Guest (using 1 CPU) was still showing that it has a 2 GHz CPU in
> /proc/cpuinfo (I guess this value is read only once, when booting).
>
> After about 2 hours I started "date" on the guest - it showed that it's
> year *1953*, after which I couldn't start any other command (the guest
> was technically alive - SSH connection to it didn't die - but I couldn't
> do anything).
>
> # date
> Wed Feb 18 13:07:17 CET 2009
>
> [let's wait ~2 hours]
>
>
> # date
> Fri May 15 10:13:14 CET 1953
> # date
> ^C^Z
> [could not interrupt]
>
>
> Is it expected behaviour? Is it correct behaviour?

Whats the output of /proc/cpuinfo on the host? Does it contain the
constant_tsc flag?

Whats the output of
/sys/devices/system/clocksource/clocksource0/current_clocksource
on the guest?