Re: [Xen-devel] [PATCH v3 06/11] optee: add std call handling

[Julien Grall <julien.grall@xxxxxxx>]

On 1/17/19 7:13 PM, Volodymyr Babchuk wrote:
> > > Actually, OP-TEE protocol have possibility to handle limited number of
> > > threads correctly. OP-TEE can report that all threads are busy and
> > > client will wait for a free one. XEN can do the same, although this is not
> > > implemented in this patch series. But I can add this.
> > Could you expand by wait? Will it block in OP-TEE/Xen or does it
> > return to the guest?
> It returns to the guest with response code
> OPTEE_SMC_RETURN_ETHREAD_LIMIT. Linux driver blocks calling application
> thread until one of the calls to OP-TEE is finished. Then driver awakens
> one of the blocked threads, so it can perform the call.
Shouldn't not you return this value when you reach out MAX_STD_CALLS?

Actually, looking at the code, you don't seem to return in error code 
when there are a failure in the mediator. Instead you seem to always 
return "false". Which means the virtual SMCCC framework thinks the call 
was never handled. However, this is not true, you handled the call but 
the there was a failure during it.
In general, handle_call should return false only if the call is 
non-existent. In all the other case, you should feed a proper return by 
yourself.
Cheers,

--
Julien Grall

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