Am Mon, 21 Aug 2017 17:20:56 -0700
schrieb Gustavo Lima Chaves <[email protected]>:

> Hi,
> 
> what's the intention with the current design where inmates have access
> to cell_state (COMM_REGION_GENERIC_HEADER)? Is this safe? I was able
> to replicate what apic-demo.c does WRT that in a Zephyr binary as
> well, just to be sure.

I am afraid i do not get the question. With "have access" you mean they
can read and write the value and the change becomes visible to others
i.e. hypervisor and root-cell?

There are three values that actually have a meaning and change the
behavior of the hypervisor (_FAILED, _SHUT_DOWN and RUNNING_LOCKED).
Setting itself to FAILED or SHUT_DOWN the cell would not receive
messages anymore, does not seem too bad for others. And we already
discussed what RUNNING_LOCKED is for.

Could you describe a scenario where the control of this variable is
unsafe/problematic?

> Isn't ./tools/jailhouse cell list or, better yet,
> /sys/devices/jailhouse/cells/XXX/state a means for the root cell to
> watch cell states in order to act on them (assuming "open" model from
> https://events.linuxfoundation.org/sites/events/files/slides/ELCE2016-Jailhouse-Tutorial.pdf)?
> If so, how can we trust the cells setting their states and not the
> hypervisor only?

I think the only case in which a cell would want to / have to set the
state itself is RUNNING_LOCKED. You can probably invent a few custom
states that only your cell and your rootcell sysfs watchdog know about,
if you want to have such a thing.

Maybe you have an example for the problematic case where a cell fails
to update its state causing trouble in the rest of the system?

Henning

> Regards,
> 

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