Ken,
Thank you for your prompt response. Please see my replies below.
Alan
Hi Alan, The proposed APIs are implemented for library mode. It will not work under IPC mode in 'feature-ipc' branch. The support of NSPM for IPC will come later.
Is their a feature rollout schedule that I can follow?
The TZ_LoadContext_S() and TZ_StoreContext_S() need to be called every time while secure service accessed NS thread get entering/leaving. It is not combined into one function, because not all NS threads need to access secure service. For those NS threads which do not need to access secure service, these TZ_ APIs are unnecessary to be called. For example, if NS scheduler switches from one secure service accessed thread into the other generic thread, only TZ_StoreContext_S() needs to be called before context switching.
To avoid the rather burdensome overhead of calling into the SPM twice on those NS context switches in which either the leaving or entering contexts are secure accessing threads, I propose that a NULL TZ_MemoryId_t be defined so that a single TZ_SwitchContext_S() function with two TZ_MemoryId_t arguments can be called. The NULL TZ_MemoryId_t would be passed to identify an entering or leaving context that is not secure accessing.
The method of blocking the caller client is based on scenarios. If there are some 'wait' is necessary while secure service is working (waiting for secure hardware IRQ as an example), the method you mentioned may be involved (special return value with an NS IRQ notification). This functionality is not in place right now.
-Ken
-----Original Message----- From: TF-M tf-m-bounces@lists.trustedfirmware.org On Behalf Of DeMars, Alan via TF-M Sent: Sunday, February 3, 2019 9:17 AM To: tf-m@lists.trustedfirmware.org Subject: [Tf-m] Non-secure Client Management
Regarding the Non-secure Client Management proposal:
https://developer.trustedfirmware.org/w/tf_m/design/ns_client_management/
I notice that the veneers for the proposed APIs are in s_veneers.o. Does this mean that the proposal has been adopted and implemented? Is it functional in the current feature-ipc branch?
I have a question about the TZ_LoadContext_S() and TZ_StoreContext_S() APIs: Is it expected that each context switch in the NS world will be signaled by calls to each of these APIs indicating the "entering" context and "leaving" context respectively? If so, then why not collapse these two APIs into one called TZ_SwitchContext__S() and pass both the "entering" and "leaving" TZ_MemoryId_t's as arguments?
Or is TZ_StoreContext_S() only to be called when a NS context will never call into the SPM again? If that is the case, why isn't TZ_FreeModuleContext_S() sufficient?
Regarding the "Concurrent secure service requests" discussion, what does "a non-secure client is blocked on an asynchronous secure service completion"? Would this be achieved by a special return status from psa_call() indicating that the current service request is in process and will complete later on? The psa_call() calling thread would then block on a semaphore that would be released by a dedicated NS IRQ interrupt? Is any of this functionality in place yet?
Alan
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