Hi,

On Wed, Jul 7, 2021 at 7:52 AM Sumit Garg [off-list ref] wrote:

On Tue, 6 Jul 2021 at 18:16, Marc Zyngier [off-list ref] wrote:

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- Is there any case where you would instead need a level interrupt
  (which a SGI cannot provide)?

I think SGI should be sufficient to suffice OP-TEE notifications use-case.

I don't care about OP-TEE. If you are proposing a contract between S
and NS, it has to be TEE and OS independent. That's how the
architecture works.

Agree, here we are not proposing a common contract among the S and NS
world that every TEE (based on Arm TrustZone) will use to communicate
with REE (Linux in our case) but rather an OP-TEE specific
notifications feature that is built on top of OP-TEE specific ABIs.

And I can see your arguments coming from an FFA perspective but there
are platforms like the ones based on Armv7 which don't support FFA
ABI. Maybe Jens can elaborate how this feature will fit in when FFA
comes into picture?

OP-TEE has one official ABI at the moment, the SMC based one. It's
about to get another one based on FF-A instead. The two ABIs will
never be used at the same time. It's a build time option for the
OP-TEE firmware to either use SMC or FF-A based communication.

The patches I've posted here concern the SMC based ABI. Asynchronous
notification in OP-TEE with a FF-A based ABI will use the notification
framework provided by FF-A instead to implement that counterpart
provided by these patches. So the OP-TEE driver here in the kernel
will use the FF-A framework in the kernel instead of registering an
interrupt handler directly.

Cheers,
Jens

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