Hi Stuart,
On 12/05/2017 03:36 PM, Stuart Yoder wrote:
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.
Thank you for the explanation. I see you specifically mention the
hypervisor timer tick. How about the other interrupts? Will OP-TEE halts
the current in-progress thread and then return to Xen/OS?
Cheers,
--
Julien Grall
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