On 20 Nov 2020, at 03:28, Demi M. Obenour <[email protected]> wrote:
> 
> The first is an explanation for why the restrictions stated are
> acceptable.  For instance, it is clear that the targeted systems are
> static.  Why is dynamism not required?  Is it because these systems
> are created with a single purpose in mind, and so do not need the
> level of extensibility that a dynamic system offers?

As the design document states: It’s meant to be simple but sufficient for the 
target domains. More generality means more complexity. The proposed model 
should serve almost all present use cases. Even Cog System’s “ultra-secure 
phone" fits this model: All the dynamicism, such as run-time installable apps, 
happen inside a virtual machine with an Android guest. From the seL4 PoV, the 
phone is a simple, static architecture with a fixed number of protected 
components: the “use VM” containing a full Android system with virtual drivers, 
the VMM, a console, a I/O multiplexing component, a “driver VM” (which should 
eventually become individual driver components), a network encryption component 
and a storage encryption VM. If the Platform supports this use case, it will 
definitely support most others.

For the (presently very small) class of deployments that need more generality, 
a different framework is needed. Such more general frameworks may be 
standardised in the future (and may or may not be extensions of the Core 
Platform), but for now this is not the aim. If you want a system where a fully 
general OS is needed, Genode is likely your best choice (at the expense of 
losing most of the assurance).

> The second is the ability to forcibly reset a protection domain to
> its initial state.  […]

As the RFC clearly spells out, this is “a first step”, we won’t get very far 
trying to boil the ocean. Re-initialising components is definitely planned, but 
for a future release (see the last few minutes of my talk at the seL4 Summit: 
https://www.youtube.com/watch?v=khcjH77riGA&list=PLtoQeavghzr1Z3mF5B-f_xnFm81MPPwA-&index=4
 
<https://www.youtube.com/watch?v=khcjH77riGA&list=PLtoQeavghzr1Z3mF5B-f_xnFm81MPPwA-&index=4>).

Gernot

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