Hi Henning.

Thank you for answering. 

> -----Mensaje original-----
> De: Henning Schild <[email protected]> 
> Enviado el: jueves, 4 de noviembre de 2021 14:56
> Para: Raimundo Sagarzazu <[email protected]>
> CC: [email protected]
> Asunto: Re: Problem: system hangs
>
>
> Am Thu, 4 Nov 2021 11:47:00 +0000
> schrieb Raimundo Sagarzazu <[email protected]>:
>
>> Hello all,
>> 
>> I'm experiencing a "system hanging" problem when jalhouse is enabled.
>> It happens with just rootcell enabled, no need to start inmate cells.
>> I've been working on it for several weeks trying to have at least an
>> error log or report but I didn't success. System just freezes.
>
> You should see what happens without jailhouse. If the hypervisor was
> blocking any access to anything, it would tell you. So it might be that
> it in fact has nothing to do with jailhouse.
>

I agree with you but I'm not able to reproduce de problem if jailhouse is 
disabled. Even if after having the jailhouse rootcell enabled and successfully 
working I disable it back (jailhouse disable), the system never hangs. It has 
been running for several days doing more than 500000 launches/kills.

>> I'm able to reproduce it by launching and killing an application
>> repeatedly. It hangs when launching, not when killing, so I'm
>> thinking it could happen when trying to access an invalid memory
>> region. Could be?
>> 
> Unlikely because applications can not directly use physical memory.
> Unless you have an application using "/dev/mem". In fact you can try a
> dd of /dev/mem and break out ... i bet you would see a hypervisor
> violation and not just a hang.
>
> "dd if=/dev/mem of=/dev/null bs=1 count=1 seek=<address not allowed
> for that cell>"
>
>> Sometimes it arrives quit easily,  just after some launches but
>> sometimes it can take several hours, more than 7000 launches ...
>
> Sounds more like a memory leak or something, a memory leak would also
> show quicker when running under jailhouse (with reduces memory).
>
> I suggest to valgrind that application, or just keep an eye on "free"
> as you re-launch. Regular applications should not be a problem, but say
> that application re-loads a leaky kernel module ...
>

The freeze occurs with different applications (some examples of Qt5, some demos 
of mesa, ...) but it seems to happen just when using the graphics acceleration 
(opengl).

If, for example, the application is launched through wayland+weston but 
acceleration is disabled (--use-pixman option in weston), there is no hanging. 
On the other hand, if acceleration is enabled the problem happens with X server 
or wayland display.

I checked all iommu related configs on the kernel but I don't see anything 
wrong.

Maybe something to do with drm i915 kernel driver side?

> regards,
> Henning

Best regards,

  Rai.


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