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Re: [Xen-devel] [ARM] Native application design and discussion (I hope)

Hello All,

On 10.05.17 12:56, George Dunlap wrote:
But the context here is that Andrii asked something about whether this
"EL0 App" functionality could be used to service Xen as well as a
domain.  You said it didn't make sense, and Dario (as I understand it)
was pointing out that we already did something similar with tasklets.
If there was a need to be able to "upload" user-specified routines that
would handle events generated by the hypervisor rather than events
generated by a guest, that would indeed be a possibility.  It would
essentially be the equivalent of a deprivileged, untrusted tasklet.
Actually that is what we are heavily interested in.
One more pro for a generic EL0 apps is that they could have different from XEN license. I.e. proprietary one.

At the moment I can't foresee the need for such a mechanism, and I don't
particularly think that we should keep that use case in mind when
designing the "App" interface.  But it is an interesting idea to keep in
our back pockets in case a use case comes up later.
I would provide few examples we have on the table:

 * fdtlib mentioned here [1] - just an example of a piece of some
   untrusted but virtually needed code.
 * a coprocessor platform support for SCF [2][3] - probably will be a
   piece of proprietary code, due to such IP specific functionalities
   like coprocessor task switching sequence and mmio access emulation.
 * some tee support code - support of trustee or mshield - proprietary one.

[1] https://lists.xenproject.org/archives/html/xen-devel/2017-05/msg00381.html [2] https://lists.xenproject.org/archives/html/xen-devel/2016-10/msg01966.html [3] https://lists.xenproject.org/archives/html/xen-devel/2017-05/msg00348.html


*Andrii Anisov*

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