Re: [Xen-devel] Reproducible hang with cstate disabled

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.11.15 at 06:47, <srn@xxxxxxxxx> wrote:
> I saw xen hang after
> 
> (XEN) HVM: HAP page sizes: 4kB, 2MB, 1GB
> (
> 
> The line that's supposed to be there is
> 
> (XEN) Brought up 24 CPUs
> 
> After power cycling I went into the BIOS. In the BIOS, C-STATE was disabled. 
> I changed it to
> 
> * Intel(R) C-STATE tech          [Enabled]
> * C3 State                       [ACPI C2]
> * C6 State                       [Enabled]
> * C State package limit setting  [Auto]
> * C1 Auto Demotion               [Disabled]
> * C3 Auto Demotion               [Disabled]
> 
> After making the above changes it booted up correctly.
> I turned C-STATE off again and it hung at the same place.
> I turned C-STATE back on and it worked again.

Interesting, but first of all this smells like a hardware or firmware
issue. Did you try booting with "no-mwait-idle" or one of its
equivalents? I ask because that driver is independent of any
BIOS settings.

Did you further try fiddling with any of the other settings you
quote above? Or limiting the maximum C state on the Xen
command line?

And finally, does "sync_console watchdog" end up in anything
more useful than output stopping in the middle of a line?

> I have not tested on another machine yet, but I expect the same behavior.

On another identical machine probably yes. On a different one I
would doubt it.

Jan


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