March 2020 - TF-M - lists.trustedfirmware.org

Re: [TF-M] [EXTERNAL] Project Maintenance Proposal for tf.org Projects

by Shreve, Erik

Sandrine, Really glad to see this being pulled together. A couple of areas of feedback around the Platform Support Life Cycle. As previously mentioned there are two orthogonal concerns captured in the current life cycle: Support and Functionality. I'd like to see these split out. For functionality, chip vendors may not have a business case for supporting all features on a given platform but they may provide full support for the features they have chosen to include. A simple example would be supporting PSA FF Isolation Level 1 only due to lack of HW isolation support needed to achieve Isolation Level 2 or greater. Also, I'd like to see a stronger standard put forth for platform documentation. If a platform is "supported," I believe the documentation should be complete and accurate. A lack of complete and clear documentation leaves open a wide door for misuse/misconfiguration which could result in a vulnerable system. Here is a more concrete proposal: Functional Support: Each project shall provide a standard feature or functionality list. Each platform shall include in its documentation a copy of this list with the supported functionality marked as supported. The platform documentation may reference a ticket if support is planned but not yet present. The platform documentation shall explicitly state if a feature or function has no plans for support. The feature/functionality list shall be versioned, with the version tied to the release version(s) of the project. In this way, it will be clear if a platform was last officially updated for version X but the project is currently at version Y > X. Note: projects will need to adopt (if they have not already) a version scheme that distinguishes between feature updates and bug fixes. Each project and platform shall use tags or similar functionality on tickets to associate tickets to features/functionality and platforms. If the names of tags can't match the name of the feature or platform exactly then a mapping shall be provided in the appropriate document(s). Life Cycle State Fully Supported There is (at least) one active code owner for this platform. All supported features build and either all tests pass or failures are associated with tracked known issues. Other (not associated to a test) Known Issues are tracked Documentation is up to date Note: Projects should document standards on how "active" code ownership is measured and further document standards on how code owners are warned about impending life cycle state changes. Orphan There is no active code owner All supported features build and either all tests pass or failures are associated with tracked known issues. Other (not associated to a test) Known Issues may not have been maintained (as there is no active code owner) Documentation status is unclear since there is no active code owner. There has been no change to the feature/functionality list in the project since the platform was last "Fully Supported" Out of date Same as orphan, but either: there have been changes to the feature/functionality list, or there are failing tests without tracked tickets, or there are known documentation issues. Deprecated Same as Out of Date, but the build is broken. Platform may be removed from the project codebase in the future. Erik Shreve, PSEM Software Security Engineer & Architect (CMCU Platform Development) -----Original Message----- From: TF-M [mailto:tf-m-bounces@lists.trustedfirmware.org] On Behalf Of Sandrine Bailleux via TF-M Sent: Tuesday, March 24, 2020 4:42 AM To: tf-a; tf-m(a)lists.trustedfirmware.org; tsc(a)lists.trustedfirmware.org; op-tee(a)linaro.org Cc: nd(a)arm.com Subject: [EXTERNAL] [TF-M] Project Maintenance Proposal for tf.org Projects Hello all, As the developers community at trustedfirmware.org is growing, there is an increasing need to have work processes that are clearly documented, feel smooth and scale well. We think that there is an opportunity to improve the way the trustedfirmware.org projects are managed today. That's why we are sharing a project maintenance proposal, focusing on the TF-A and TF-M projects initially. The aim of this document is to propose a set of rules, guidelines and processes to try and improve the way we work together as a community today. Note that this is an early draft at this stage. This is put up for further discussion within the trustedfirmware.org community. Nothing is set in stone yet and it is expected to go under change as feedback from the community is incorporated. Please find the initial proposal here: https://developer.trustedfirmware.org/w/collaboration/project-maintenance-p… Please provide any feedback you may have by replying to this email thread, keeping all 4 mailing lists in the recipients list. I will collate comments from the community and try to incorporate them in the document, keeping you updated on changes made between revisions. Regards, Sandrine -- TF-M mailing list TF-M(a)lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/tf-m

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Re: [TF-M] Project Maintenance Proposal for tf.org Projects

by Christian Daudt

Hi Sandrine, > Please find the initial proposal here: > > https://developer.trustedfirmware.org/w/collaboration/project-maintenance-p… > > Please provide any feedback you may have by replying to this email > thread, keeping all 4 mailing lists in the recipients list. > > I will collate comments from the community and try to incorporate them > in the document, keeping you updated on changes made between revisions. The maintenance proposal looks great ! I have some feedback on specific portions: 1. maintainer/owner/author patches. " Note that roles can be cumulative, in particular the same individual can be both a code owner and a maintainer. In such a scenario, the individual would be able to self-merge a patch solely affecting his module, having the authority to approve it from both a code owner and maintainer's point of view.": I'm always leery of people self-approving their patches. At a minimum, all self-patches should be published and a minimum wait time provided for feedback. Or preferably that another maintainer does the merge (it does not need to be mandated but should be suggested). 2. 'timely manner': This expectation should be more explicit - when the author can start requesting other maintainers to merge on assumption that silence == approval (or not). Such timeliness expectations are probably best set per project however. 3. The proposal does not address branching strategies. i.e. will there be separate maintainers for dev/master/stable branches? I don't think it needs to address it yet - keep it simpler for a start. But a todo saying something like "in the future this project maintenance proposal might be expanded to address multi-branch maintainership" would be good. 4. The platform lifecycle state machine has too many transitions. "Fully maintained" <-> "orphan" -> "out" seems sufficient to me. Thanks, Christian. This message and any attachments may contain confidential information from Cypress or its subsidiaries. If it has been received in error, please advise the sender and immediately delete this message.

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Slight update on design proposal process document

by Ken Liu

Hi, I have made a slight update on the design proposal process document, to simplify the design document drafting. The 'Author' and 'Organization' are not both mandatory, one of them can be optional depends on the contributor. And mark the 'status' optional since it can be covered by the document system. Feel free to comment on the patch: https://review.trustedfirmware.org/c/trusted-firmware-m/+/3407 And I prefer to comment on the issue link since there is more better for discussion: https://developer.trustedfirmware.org/T673 Reply here is an option, too. BR /Ken

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TF-M v1.0 is released

by Anton Komlev

Dear All, Happy to announce that Trusted Firmware - M project has reached the important milestone of v1.0. The major features covered in this release are : * PSA Level 1 & Level 2 certification requirements as updatable RoT * Support for PSA Dev APIs (PS, ITS, Attestation) aligned to PSA 1.0 specs, and Crypto aligned to 1.0-beta-3 * Reference implementation on various platforms * Arm : Musca-A, Musca-B1, Musca-S1, FPGAs , FVPs * Cypress PSoC6 * ST's STM32L5 and NXP's LPC55S69 are coming soon All release details are in the changelog file: https://git.trustedfirmware.org/trusted-firmware-m.git/tree/docs/changelog.… A Rendered HTML version is here: https://ci.trustedfirmware.org/job/tf-m-build-test-nightly/lastSuccessfulBu… This is the result of great collaboration between multiple organizations toward a single common goal - to make firmware secure and trustful. Thanks all direct and indirect contributors who devoted their time and efforts to make this happen. Anton Komlev TF-M Technical Leader Arm Ltd.

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Re: [TF-M] Multi-threaded single-scheduler model proposal

by Shreve, Erik

Ken, Thanks for the feedback! I agree that care will be needed in the design and implementation of the calls from S to NS. I hope to provide design details that minimize the risk by minimizing the RTOS specific layer. Unfortunately, I'm not clear on your feedback about the 'scheduler' and 'context-switch' terms. Let me expand on my proposal here a bit more. Perhaps this will clarify things or at least provide enough detail for you to provide more specific feedback. I'm sure you are aware that the PSA Firmware Framework provides for the scheduling of the secure partitions. I'm proposing (as an option, it is not a core feature of the proposal) that the SPM may be responsible for scheduling of Application Root of Trust services in this new model. Further, execution of PSA RoT services on behalf of Application RoT services may also fall under the SPM's scheduling. Thus, this part of the new model would fit with the PSA FF spec. This would thus mean that the NSPE RTOS is only scheduling NSPE Tasks and the associated PSA RoT service requests for those NSPE Tasks. However, supporting the "App RoT scheduling by SPM" in the model may complicate the implementation or at the very least the straightforward understanding of how the model works. The alternative, of course, is that the NSPE RTOS schedules the execution of the Application RoT services the same as it schedules the PSA RoT services. I think I prefer the latter, but I'm open to the former if the community has good reasons for it. One reason might be an expectation that PSA RoT services will be maintained by platform owners and platform owners can choose which models to support, but the community may want creators of Application RoT services to have the same experience regardless of the model implemented. Thanks! Erik Shreve, PSEM Software Security Engineer & Architect (CMCU Platform Development) From: TF-M [mailto:tf-m-bounces@lists.trustedfirmware.org] On Behalf Of Ken Liu via TF-M Sent: Monday, March 23, 2020 9:49 PM To: 'tf-m(a)lists.trustedfirmware.org' Cc: nd Subject: [EXTERNAL] Re: [TF-M] Multi-threaded single-scheduler model proposal Hi Erik, This is a good proposal, thanks. And I got two comments in your listed bullets: * Resource locking APIs are provided to allow PSA RoT functions to communicate with the NSPE scheduler (i.e. mutex take/give) - Even the Trustzone-M supports S to NS call, be cation when you are designing such features because leave a waiting pattern in the secure side exposes one extra interface. * A SPE scheduler may still exist for application root of trust services, if any exist on a system. - Please use the 'scheduler' and 'context-switch' with scope. If there are 2 threads only and just switching contexts between them, the word 'scheduler' would be a bit confusing here. Hope my assumption is incorrect. Please go ahead with your preparation for the Tech Forum. Anton can give you detail descriptions about it and I think preparing a PUBLIC slide can be the first step. Thanks. /Ken From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org> On Behalf Of Shreve, Erik via TF-M Sent: Tuesday, March 24, 2020 5:26 AM To: tf-m(a)lists.trustedfirmware.org Cc: nd <nd(a)arm.com> Subject: Re: [TF-M] Multi-threaded single-scheduler model proposal Anton, Yes, I can be prepared to discuss in the next forum. (I believe you are referring to the one on April 2nd). I've not participated in the forums yet, please send me some information as to the format/rules/etc. Thanks! Erik Shreve, PSEM Software Security Engineer & Architect (CMCU Platform Development) From: TF-M [mailto:tf-m-bounces@lists.trustedfirmware.org] On Behalf Of Anton Komlev via TF-M Sent: Monday, March 23, 2020 3:39 PM To: tf-m(a)lists.trustedfirmware.org<mailto:tf-m@lists.trustedfirmware.org> Cc: nd Subject: [EXTERNAL] Re: [TF-M] Multi-threaded single-scheduler model proposal Hi Erik, Thanks for proposing improvements to TF-M, cooperative scheduling namely. You hit the topic which was considered but postponed at some moment. Believe, it will be beneficial to all of us to discuss it online and share our views on potential improvement and possible side effects. Let me know, please, if you want to include this topic into next forum agenda? Kind regards, Anton Komlev From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org<mailto:tf-m-bounces@lists.trustedfirmware.org>> On Behalf Of Shreve, Erik via TF-M Sent: 23 March 2020 14:26 To: tf-m(a)lists.trustedfirmware.org<mailto:tf-m@lists.trustedfirmware.org> Subject: [TF-M] Multi-threaded single-scheduler model proposal I'd like to propose an additional model that provides a single-scheduler _and_ multiple thread support for PSA RoT. To state a little more specifically: * The NSPE scheduler makes all scheduling decisions for execution (call) flows of the NSPE tasks - including when those flows are operating in secure side * APIs are provided to the NSPE scheduler to switch SPE task contexts (one task context associated to each NSPE task that uses PSA RoT) * Resource locking APIs are provided to allow PSA RoT functions to communicate with the NSPE scheduler (i.e. mutex take/give) * A SPE scheduler may still exist for application root of trust services, if any exist on a system. I don't see anything written up on a model like this in the design proposals or Phabricator. However, it appears to me that such a model (or something similar) must have been previously discussed. 1. There already exists a tz_context API set in CMSIS-Core for communicating task switches by the NSPE scheduler to the SPM 2. Cooperative scheduling rules design was accepted: https://ci.trustedfirmware.org/job/tf-m-build-test-nightly/lastSuccessfulBu… 3. https://youtu.be/6wEFoq49qUw?t=1671 speaks about having a stack on the SPE per NSPE task. Also, the question from the audience at the end of the presentation relates to having a single NSPE scheduler. A brief word on the motivation for such a proposal... To ease (and thus increase) adaptation of PSA RoT, wherein those services are protected from nontrusted code, the impact to the NSPE code should be minimized. The current models (Library, IPC) do well to minimize the impact from an API standpoint. That is, the NSPE caller need not know where/how the PSA RoT operates in order to compile. However, the current models do not minimize impact to scheduling on single core systems. The library model locks behind a single mutex the operations that previously existed independent of one another. The IPC model provides more flexibility. However, it still extends lock times beyond current implementations and it introduces an additional scheduler which removes determinism and forces system designers to rethink existing code. I'd like to know if there are any recorded plans for such a model (or something more similar to it than the three items above). If not, has it been discussed and actively rejected? If so why? I can/will write up a more concrete proposal, but wanted to get some discussion around the high-level idea first. Thanks, Erik Shreve, PSEM Software Security Engineer & Architect (CMCU Platform Development) Texas Instruments Inc. 12500 TI Boulevard, MS F4000 Dallas, TX 75243

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Invitation: TF-M Tech Forum @ Thu 2 Apr 2020 16:00 - 17:00 (BST) (tf-m@lists.trustedfirmware.org)

by Bill Fletcher

You have been invited to the following event. Title: TF-M Tech Forum After a discussion on the mailing list we have moved the timeslot this week to give an opportunity for US participants to join.About TF-M Tech forum:This is an open forum for anyone to participate and it is not restricted to Trusted Firmware project members. It will operate under the guidance of the TF TSC.Feel free to forward it to colleagues.Details of previous meetings are here: https://www.trustedfirmware.org/meetings/tf-m-technical-forum/Tr… Firmware is inviting you to a scheduled Zoom meeting.Join Zoom Meetinghttps://zoom.us/j/9159704974Meeting ID: 915 970 4974One tap mobile+16465588656,,9159704974# US (New York)+16699009128,,9159704974# US (San Jose)Dial by your location        +1 646 558 8656 US (New York)        +1 669 900 9128 US (San Jose)        877 853 5247 US Toll-free        888 788 0099 US Toll-freeMeeting ID: 915 970 4974Find your local number: https://zoom.us/u/ad27hc6t7h When: Thu 2 Apr 2020 16:00 – 17:00 United Kingdom Time Calendar: tf-m(a)lists.trustedfirmware.org Who: * Bill Fletcher- creator * tf-m(a)lists.trustedfirmware.org Event details: https://www.google.com/calendar/event?action=VIEW&eid=NmY2dWZkbzZtMjZyNHNmb… Invitation from Google Calendar: https://www.google.com/calendar/ You are receiving this courtesy email at the account tf-m(a)lists.trustedfirmware.org because you are an attendee of this event. To stop receiving future updates for this event, decline this event. Alternatively, you can sign up for a Google Account at https://www.google.com/calendar/ and control your notification settings for your entire calendar. Forwarding this invitation could allow any recipient to send a response to the organiser and be added to the guest list, invite others regardless of their own invitation status or to modify your RSVP. Learn more at https://support.google.com/calendar/answer/37135#forwarding

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Re: [TF-M] TF-M Technical Forum call - April 2

by David Wang

That sounds good! Thanks. Regards, David Wang Arm Electronic Technology (Shanghai) Co., Ltd Phone: +86-21-6154 9142 (ext. 59142) From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org> On Behalf Of Anton Komlev via TF-M Sent: Tuesday, March 24, 2020 1:46 AM To: Jamie Fox <Jamie.Fox(a)arm.com>; tf-m(a)lists.trustedfirmware.org Cc: nd <nd(a)arm.com> Subject: Re: [TF-M] TF-M Technical Forum call - April 2 Hi Jamie, Thanks for noticing. You are right, that time would be better so the new proposal is 15.00 UTC. I have reused the time from the last session but forgot about the time change. Here anyone can play with the time zones: https://www.timeanddate.com/worldclock/meetingtime.html?day=2&month=4&year=… Location Local Time Time Zone UTC Offset Vancouver<https://www.timeanddate.com/worldclock/canada/vancouver> (Canada - British Columbia) Thursday, 2 April 2020, 08:00:00 PDT<https://www.timeanddate.com/time/zones/pdt> UTC-7 hours Chicago<https://www.timeanddate.com/worldclock/usa/chicago> (USA - Illinois) Thursday, 2 April 2020, 10:00:00 CDT<https://www.timeanddate.com/time/zones/cdt> UTC-5 hours Cambridge<https://www.timeanddate.com/worldclock/uk/cambridge> (United Kingdom - England) Thursday, 2 April 2020, 16:00:00 BST<https://www.timeanddate.com/time/zones/bst> UTC+1 hour Shanghai<https://www.timeanddate.com/worldclock/china/shanghai> (China - Shanghai Municipality) Thursday, 2 April 2020, 23:00:00 CST<https://www.timeanddate.com/time/zones/cst-china> UTC+8 hours Corresponding UTC (GMT) Thursday, 2 April 2020, 15:00:00<https://www.timeanddate.com/worldclock/fixedtime.html?iso=20200402T1500> Best regards, Anton From: Jamie Fox <Jamie.Fox(a)arm.com<mailto:Jamie.Fox@arm.com>> Sent: 23 March 2020 17:29 To: Anton Komlev <Anton.Komlev(a)arm.com<mailto:Anton.Komlev@arm.com>>; tf-m(a)lists.trustedfirmware.org<mailto:tf-m@lists.trustedfirmware.org> Cc: nd <nd(a)arm.com<mailto:nd@arm.com>> Subject: RE: TF-M Technical Forum call - April 2 Hi Anton, As we will have moved to daylight saving time in US and Europe, it seems like 15.00 UTC could be a good compromise for this next session. Would result in 8.00 west coast/10.00 central/11.00 east/16.00 UK/17.00 Europe/23.00 China. So good times for US/Europe and still possible for China to join if anyone really wants to. What do you think? Kind regards, Jamie From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org<mailto:tf-m-bounces@lists.trustedfirmware.org>> On Behalf Of Anton Komlev via TF-M Sent: 23 March 2020 14:30 To: tf-m(a)lists.trustedfirmware.org<mailto:tf-m@lists.trustedfirmware.org> Cc: nd <nd(a)arm.com<mailto:nd@arm.com>> Subject: [TF-M] TF-M Technical Forum call - April 2 Hello, Last 3 sessions of the Tech Forum were convenient for Europe – Asia time zones, where majority of participants are. To let US members a chance to join at a reasonable time, propose to have the next session at US-friendly time (17:00 UTC) and then keep it every 4th, having 1:3 ratio. What do you think about such schema? As usual, please reply to this email with your proposals for agenda topics. Best regards, Anton Komlev

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Project Maintenance Proposal for tf.org Projects

by Sandrine Bailleux

Hello all, As the developers community at trustedfirmware.org is growing, there is an increasing need to have work processes that are clearly documented, feel smooth and scale well. We think that there is an opportunity to improve the way the trustedfirmware.org projects are managed today. That's why we are sharing a project maintenance proposal, focusing on the TF-A and TF-M projects initially. The aim of this document is to propose a set of rules, guidelines and processes to try and improve the way we work together as a community today. Note that this is an early draft at this stage. This is put up for further discussion within the trustedfirmware.org community. Nothing is set in stone yet and it is expected to go under change as feedback from the community is incorporated. Please find the initial proposal here: https://developer.trustedfirmware.org/w/collaboration/project-maintenance-p… Please provide any feedback you may have by replying to this email thread, keeping all 4 mailing lists in the recipients list. I will collate comments from the community and try to incorporate them in the document, keeping you updated on changes made between revisions. Regards, Sandrine

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Re: [TF-M] TF-M Profile Small design document under review

by Andrej Butok

Hi David, I have attached the Mbed-Crypto configuration file, which enables only minimum set of crypto algorithms required to pass the current TFM regression tests. It saves us about 30KB of ROM if to compare to the default TFM settings. Hope, it can be useful for others. Regards, Andrej Butok From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org> On Behalf Of David Hu via TF-M Sent: Tuesday, March 24, 2020 7:37 AM To: tf-m(a)lists.trustedfirmware.org Cc: nd <nd(a)arm.com> Subject: [TF-M] TF-M Profile Small design document under review Hi all, Could you please help review the latest design document of TF-M Profile Small (previously named as Profile 1)? TF-M Profile Small provides a predefined list of features with small memory footprint, on ultra-constrained device. Major changes since last version: * Renamed as Profile Small to avoid confusing readers with other similar terms. The other profiles will be named as Profile Medium and Profile Large. * Enable symmetric key algorithms based Initial Attestation. Please help review the document on https://review.trustedfirmware.org/c/trusted-firmware-m/+/3598<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Freview.tr…> for more details. The corresponding implementation patch set is also updated on https://review.trustedfirmware.org/q/topic:%22profile-s-config%22+(status:o…<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Freview.tr…>. Any suggestion or comment is welcome! Best regards, Hu Ziji From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org<mailto:tf-m-bounces@lists.trustedfirmware.org>> On Behalf Of David Hu via TF-M Sent: Friday, March 6, 2020 4:47 PM To: tf-m(a)lists.trustedfirmware.org<mailto:tf-m@lists.trustedfirmware.org> Cc: nd <nd(a)arm.com<mailto:nd@arm.com>> Subject: [TF-M] TF-M Profile 1 design document under review Hi all, As we discussed in Tech Forum yesterday, we proposed the TF-M Profile 1 design document on https://review.trustedfirmware.org/c/trusted-firmware-m/+/3598<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Freview.tr…>. Any comment, suggestion or question is welcome. We will keep updating and finalizing the document. The corresponding TF-M Profile 1 implementation patch set is also under review on https://review.trustedfirmware.org/q/topic:%22profile-1-config%22+(status:o…<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Freview.tr…>. Best regards, Hu Ziji

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Re: [TF-M] Multi-threaded single-scheduler model proposal

by Anton Komlev

Hi Erik, Right, I had in mind the next forum on Apr 2, which is planned for US time zone. Invitations will be send soon having no more ideas or objection on the time slot. The forum format is open and quite unformal. You can find the recordings of all sessions here: https://www.trustedfirmware.org/meetings/tf-m-technical-forum/ I would suggest to have few slides with the concept for idea introduction and references during discussion. All the best, Anton Komlev From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org> On Behalf Of Shreve, Erik via TF-M Sent: 23 March 2020 21:26 To: tf-m(a)lists.trustedfirmware.org Cc: nd <nd(a)arm.com> Subject: Re: [TF-M] Multi-threaded single-scheduler model proposal Anton, Yes, I can be prepared to discuss in the next forum. (I believe you are referring to the one on April 2nd). I've not participated in the forums yet, please send me some information as to the format/rules/etc. Thanks! Erik Shreve, PSEM Software Security Engineer & Architect (CMCU Platform Development) From: TF-M [mailto:tf-m-bounces@lists.trustedfirmware.org] On Behalf Of Anton Komlev via TF-M Sent: Monday, March 23, 2020 3:39 PM To: tf-m(a)lists.trustedfirmware.org<mailto:tf-m@lists.trustedfirmware.org> Cc: nd Subject: [EXTERNAL] Re: [TF-M] Multi-threaded single-scheduler model proposal Hi Erik, Thanks for proposing improvements to TF-M, cooperative scheduling namely. You hit the topic which was considered but postponed at some moment. Believe, it will be beneficial to all of us to discuss it online and share our views on potential improvement and possible side effects. Let me know, please, if you want to include this topic into next forum agenda? Kind regards, Anton Komlev From: TF-M <tf-m-bounces(a)lists.trustedfirmware.org<mailto:tf-m-bounces@lists.trustedfirmware.org>> On Behalf Of Shreve, Erik via TF-M Sent: 23 March 2020 14:26 To: tf-m(a)lists.trustedfirmware.org<mailto:tf-m@lists.trustedfirmware.org> Subject: [TF-M] Multi-threaded single-scheduler model proposal I'd like to propose an additional model that provides a single-scheduler _and_ multiple thread support for PSA RoT. To state a little more specifically: * The NSPE scheduler makes all scheduling decisions for execution (call) flows of the NSPE tasks - including when those flows are operating in secure side * APIs are provided to the NSPE scheduler to switch SPE task contexts (one task context associated to each NSPE task that uses PSA RoT) * Resource locking APIs are provided to allow PSA RoT functions to communicate with the NSPE scheduler (i.e. mutex take/give) * A SPE scheduler may still exist for application root of trust services, if any exist on a system. I don't see anything written up on a model like this in the design proposals or Phabricator. However, it appears to me that such a model (or something similar) must have been previously discussed. 1. There already exists a tz_context API set in CMSIS-Core for communicating task switches by the NSPE scheduler to the SPM 2. Cooperative scheduling rules design was accepted: https://ci.trustedfirmware.org/job/tf-m-build-test-nightly/lastSuccessfulBu… 3. https://youtu.be/6wEFoq49qUw?t=1671 speaks about having a stack on the SPE per NSPE task. Also, the question from the audience at the end of the presentation relates to having a single NSPE scheduler. A brief word on the motivation for such a proposal... To ease (and thus increase) adaptation of PSA RoT, wherein those services are protected from nontrusted code, the impact to the NSPE code should be minimized. The current models (Library, IPC) do well to minimize the impact from an API standpoint. That is, the NSPE caller need not know where/how the PSA RoT operates in order to compile. However, the current models do not minimize impact to scheduling on single core systems. The library model locks behind a single mutex the operations that previously existed independent of one another. The IPC model provides more flexibility. However, it still extends lock times beyond current implementations and it introduces an additional scheduler which removes determinism and forces system designers to rethink existing code. I'd like to know if there are any recorded plans for such a model (or something more similar to it than the three items above). If not, has it been discussed and actively rejected? If so why? I can/will write up a more concrete proposal, but wanted to get some discussion around the high-level idea first. Thanks, Erik Shreve, PSEM Software Security Engineer & Architect (CMCU Platform Development) Texas Instruments Inc. 12500 TI Boulevard, MS F4000 Dallas, TX 75243

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