Re: [Xen-devel] [RFC] WIP: optee: add OP-TEE mediator

[Stuart Yoder <stuart.yoder@xxxxxxx>]

> > There are limit on pCPUs, though. But this is not a problem, because
> > XEN scheduler will decide which guest will access OP-TEE right now.
> > OP-TEE don't have own scheduler at all, by the way. It is scheduled
> > by normal world.
> Do you mind to give a bit more explanation here? Do you plan to add knowledge 
> of OP-TEE in the scheduler?
Regarding scheduling-- OP-TEE runs with interrupts enabled (generally).  So 
when an SMC
is in process in OP-TEE and the normal OS or hypervisor timer tick fires, 
OP-TEE halts
the current the in-progress thread, saves states, and returns to the normal 
world to
let the normal world timer interrupt handler and scheduler do its normal thing. 
 Eventually
when the normal world thread is re-scheduled and the in-progress thread 
restarts the
SMC.  That process continues until the SMC is completely done. So the OS/VMM 
scheduler
needs no awareness of OP-TEE since OP-TEE is cooperating with the normal world.

Stuart



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