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Re: [Xen-devel] [PATCH v2 09/13] optee: add support for arbitrary shared memory





On 09/12/2018 01:45 PM, Volodymyr Babchuk wrote:
Hi,

Hi Volodymyr,

On 12.09.18 14:02, Julien Grall wrote:
On 09/11/2018 08:33 PM, Volodymyr Babchuk wrote:
However, 2MB might be too big considering that you also need to account the SMC call. Does buffer can be passed for fast call?
No, all such calls are yielding calls, so you can ignore time used for SMC call itself.

How come you can ignore it? It has a cost to trap to EL3.
Strictly speaking, yes. All steps has cost: trap to EL3, dispatch in EL3,
switch to S-EL1, new thread preparation in OP-TEE, context switch in OP-TEE. I wanted to tell, that in my opinion, this is negligible in comparison with the actual call processing. But maybe, I'm wrong there.

It would be interesting to have a breakdown on the time spent in the call (with virtualization). Did you have a chance to do that?

Cheers,

--
Julien Grall

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