On 18/06/2019 12:19, Volodymyr Babchuk wrote:
Hi Julien,
Hi,
Julien Grall writes:
+=item B<optee>
+Allow a guest to use OP-TEE. Note that a virtualization-aware OP-TEE +is required for this. If this option is selected, guest will be able
OOI, what happen if OP-TEE does not support virtualization. Will Xen forbid to use it?
Yes, Xen will get an error from OP-TEE during domain construction. This will lead to domain creation failure.
This is a bit odd. It means we have no way to know in advance whether OP-TEE will be able to create a client. In other word, when the mediator is built in Xen, all existing setup with OP-TEE (and no-virtualization) will fail.
My expectation is Xen should be able to know whether the mediator can be used.
+to access to the real OP-TEE OS running on the host. Guest creation
s/real// it is redundant with the rest of the sentence. However, it does not really answer to the question regarding isolation.
Your assumption is correct - OP-TEE provides isolation on its side.
+will fail if OP-TEE have no resources for a new guest. Number of supported +guests depends on OP-TEE configuration.
How about the following description (correct me if my understanding is wrong):
"Allow a guest to access the host OP-TEE OS. Xen will mediate the access to OP-TEE and the resource isolation will be provided directly by OP-TEE. OP-TEE itself may limit the number of guests that can concurrently use it. This requires a virtualization-aware OP-TEE for this to work.
This feature is a B<technology preview>."
That's much better than my version. Thank you.
How can a user know whether OP-TEE supports virtualization? Is it configurable at build?
Yes, there is a special configuration option CFG_VIRTUALIZATION. This is covered in OP-TEE documentation at [1]
[1] https://optee.readthedocs.io/architecture/virtualization.html
Do we expect the link to be stable? If so, then I think a link in the documentation would be useful.
Cheers,