Re: [Xen-devel] [hybrid]: hang in update_wall_time

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.03.12 at 02:30, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> wrote:
> Hi Ian/Stefano:
> 
> I changed over to the PV clock for hybrid liked we talked at the
> hackathon. I still have the hang in update_wall_time() after dom0
> switches to xen as clocksource.
> 
> The source of hang seems to be in xen stime_local_stamp in cpu_time that
> suddenly jumps to a large 64bit value. I've been chasing to figure
> where that happens, and why for the hybrid and not PV. It appears the
> source of jump is time_calibration_std_rendezvous()  in 
> c->stime_master_stamp. Chasing that, seems to come from 
> read_platform_stime(). The jump happens after switch to
> xen clocksource in dom0.
> 
> I'll continue to debug, but let me know if you have any thoughts or
> idea what might be going on.

Your Dom0 hasn't possibly played with the HPET, and Xen at the same
time is using the HPET as clock source? (Preventing this is rather
difficult, as the HPET memory space - iirc - is just 1k, so excluding
Dom0 access to the full page isn't easily possible. Consequently, Xen
so far has been relying on Dom0 to not get in the way.)

Jan


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