Re: soft lockup after stop/cont

[Jim Paris <jim-XrPbb/hENzg@public.gmane.org>]

Avi Kivity wrote:
> Jim Paris wrote:
> > If I stop KVM in the monitor with "stop", wait a minute, and do
> > "cont", a Linux guest gives me a "BUG: soft lockup detected on CPU#0".
> > Is that expected behavior?  
> 
> No.
> 
> > What isn't virtualized that allows it to
> > detect that?  The host is a core 2 duo.
> 
> It may be that the timer correction code detects that zillions of timer
> interrupts have not been serviced by the guest so it floods the guest
> with these interrupts.  Does -no-kvm-irqchip help?

I can't seem to reproduce the "soft lockup" at the moment, but there's
a "clocksource tsc unstable" that happens pretty reliably when I pause
the VM using stop/cont for about 15 seconds:

$ kvm -M pc -m 256 -smp 1 -boot c -hda test -net none

  stop/cont, guest reports:
    Clocksource tsc unstable (delta = 15877929568 ns)
    Time: acpi_pm clocksource has been installed.

$ kvm -no-kvm-irqchip -M pc -m 256 -smp 1 -boot c -hda test -net none

  stop/cont, guest seems not to notice.

(Host is 2.6.20.4, kvm-45 modules & userspace, guest 2.6.21)

-jim

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