I used crypto accelerator as a hypothetical example.

In a real world use case we are faced with, the process kicked off by the secure service may take a long time (ie several ms).

It is not acceptable to be parked in wfe during that time.

Alan

From: Reinhard Keil [mailto:Reinhard.Keil@arm.com]
Sent: Thursday, April 2, 2020 6:52 AM
To: DeMars, Alan; tf-m@lists.trustedfirmware.org
Cc: nd
Subject: [EXTERNAL] RE: [TF-M] Multi-threaded single-scheduler model proposal

Alan,

“I was afraid that this was the proposal. No lower priority NS threads can run while waiting for the secure interrupt. Only higher priority threads that are initiated by a NS interrupt can run.”

You are correct, scheduling of lower priority NS threads would be not possible.  This is definitely a shortcoming of the solution.

May I ask:  how long does a hardware crypto operation take?  What time could be used for low priority NS thread execution?

Reinhard