Hi Raghu,

The thing is, devicetree is already used widely on ARM and it is hard to see a good alternative. Using a C struct to describe something complicated is a pain. Take a look at the x86 setup.bin stuff, or the binary block that PowerPC used to pass to linux. Even the 'atag' tagged structure that ARM used before devicetree provides an example of the limitations of this approach. Look also at the huge tables of data passed to Intel's binary blobs (which are just chunks of UEFI, by the way) and passed back to the firmware framework, sometimes hundreds of fields across a dozen or more HOBs. C structs are good for simple things, particularly if they are not going to need to expand a lot, but devicetree provides more flexible data types and sizes, schema, human readability, expansion, tooling, future-proofing, etc. I really feel that this is self-evident, but I'm happy to go into more detail about why.

If some projects don't want to use devicetree for complex structures, that's OK. They can do their own thing and avoid talking across boundaries to other projects. When they have a need to pass complex info in a standard way to other projects once SDRAM is up, they can see whether adopting devicetree is worth it.

As I mentioned, "Blobs that were created pre-SDRAM can continue to be passed on". The proposal is just that we should not *create* new data in a blob once SDRAM is running. So we don't need to "take data from a bloblist and patch it in a devicetree".

There seems to be no benefit or need for a UUID where open collaboration is desired; in fact it appears to be designed for the opposite. The 'killer' argument provided for UUID is it allows people to allocate them in isolation without any reference to another project, which is exactly the opposite of open collaboration... So long as UUID is not *required* in any of the structures passed through the open firmware components, it seems OK to have it as an option. But it should not be *required* by ATF, etc. Specifically, U-Boot should be able to parse and generate bloblists without any UUID code. Further to that, it wouldn't make sense to use UUID to pass info from ATF to UEFI just because it is UEFI. Why not just use a tag? We have to allocate it anyway...

As to market segments, again, why? If we have a simple but sufficient solution, why not use that everywhere?

I am not sure how to respond to the part about UEFI not being private code; perhaps we just have different meanings of the word. Where is the project with all the boards supported by UEFI? U-Boot supports about 1300 with all sorts of vendors collaborating on advancing open firmware, over two decades. In any case that seems like a different topic. We don't need to discuss the merits of the different development models to come to an agreement on how to pass info between components, open or not.

Regards, SImon

On Thu, 17 Jun 2021 at 17:45, raghu.ncstate@icloud.com wrote:

My take: Don’t force device tree on platforms. Lets not make decisions about whether SDRAM is sufficient to expose device tree, that is assuming size may be the only problem with device tree. Some platforms don’t want to use device tree just like some platforms don’t want to use UUID’s(which b.t.w does not necessarily mean private use as was explained during the TF-A forums).

I support ARM’s proposal that partitions the problem based on market segments and allows different platforms to choose what is right for them, that includes the ability to use UUID if a platform so chooses AND across boundaries. I wouldn’t vote for the proposal below about using bloblist for simple things and device tree for other complex things based on SRAM/SDRAM etc. that complicates things further. What if you need to pass information from the bloblist to later boot stages? Do we take data from bloblist and patch it into a device tree?

I also think it is incorrect to partition platforms into what u-boot/linux boot/embdedded systems do and what “UEFI/private code” does. UEFI is a huge part of the ARM eco-system and is being used fairly extensively and supported across different markets and is not private code.

Thanks

-Raghu

*From:* TF-A tf-a-bounces@lists.trustedfirmware.org *On Behalf Of *François Ozog via TF-A *Sent:* Thursday, June 17, 2021 12:57 PM *To:* Simon Glass sjg@chromium.org *Cc:* Ed Stuber edstuber@amperecomputing.com; Boot Architecture Mailman List boot-architecture@lists.linaro.org; Harb Abdulhamid OS < abdulhamid@os.amperecomputing.com>; U-Boot Mailing List < u-boot@lists.denx.de>; Arjun Khare akhare@amperecomputing.com; tf-a@lists.trustedfirmware.org; Paul Isaac's paul.isaacs@linaro.org; Ron Minnich rminnich@google.com; Moe Ammar moe@amperecomputing.com *Subject:* Re: [TF-A] Proposal: TF-A to adopt hand-off blocks (HOBs) for information passing between boot stages

Le jeu. 17 juin 2021 à 21:38, Simon Glass sjg@chromium.org a écrit :

Hi,

On Fri, 11 Jun 2021 at 05:52, François Ozog francois.ozog@linaro.org wrote:

On Thu, 10 Jun 2021 at 23:57, Manish Pandey2 Manish.Pandey2@arm.com wrote:

Hi Everyone,

I have tried to conclude the discussions we had in two of the TF-A tech forum sessions and on mailing list.

The problem we are trying to solve is already solved in different projects in different ways, the purpose of these discussions was to come up with a standard way which can be adopted widely.

Considering that many Firmware projects are not DT aware its better to avoid its usage and use simple C structures for wider acceptance. Based on the discussions following design came up as most acceptable solution

• Use list of pre-defined C data structures(blobs) to pass

information, let's call it bloblist

• Only bootloaders stages will participate
• Blobs will be identified by either tags or UUIDs

They always have a tag, but one of the tags can be BLOBLISTT_UUID indicating it is for private use. But we should not allow this for passing across a boundary, so that no software needs to deal with UUID unless it is UEFI / private code. So, basically what Francios says below.

• Pass pointer to the bloblist head through x0
• Existing usage of x0 will be translated into a blob

After all discussions, I now support Simon proposal to use existing bloblist: it does the job, is already upstream in key projects (core boot, U-Boot), is supported on x86 and Arm.

I would think of a few additions on the bloblist_rec:

struct *bloblist_rec* https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/bloblist_rec {

  *u32* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/u32> *tag* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/tag>;

  *u32* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/u32> *hdr_size* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/hdr_size>;

  *u32* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/u32> size;

  *u32* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/u32> *spare* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/spare>;

};

enum *bloblist_tag_t* https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/bloblist_tag_t {

   *BLOBLISTT_NONE* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_NONE> = 0,



   */* Vendor-specific tags are permitted here */*

   *BLOBLISTT_EC_HOSTEVENT* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_EC_HOSTEVENT>,           */* Chromium OS EC host-event mask */*

We can give these each a value (=1, =2) so it is clear.

   *BLOBLISTT_SPL_HANDOFF* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_SPL_HANDOFF>,            */* Hand-off info from SPL */*

   *BLOBLISTT_VBOOT_CTX* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_VBOOT_CTX>,              */* Chromium OS verified boot context */*

   *BLOBLISTT_VBOOT_HANDOFF* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_VBOOT_HANDOFF>, */* Chromium OS internal handoff info */*

   */**

•    * Advanced Configuration and Power Interface Global Non-Volatile*
  
  

•    * Sleeping table. This forms part of the ACPI tables passed to Linux.*
  
  

•    */*
  
   *BLOBLISTT_ACPI_GNVS* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_ACPI_GNVS>,
  
   *BLOBLISTT_INTEL_VBT* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_INTEL_VBT>,              */* Intel Video-BIOS table */*
  
   *BLOBLISTT_TPM2_TCG_LOG* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_TPM2_TCG_LOG>,           */* TPM v2 log space */*
  
   *BLOBLISTT_TCPA_LOG* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_TCPA_LOG>,               */* TPM log space */*
  
   *BLOBLISTT_ACPI_TABLES* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_ACPI_TABLES>,            */* ACPI tables for x86 */*
  
   *BLOBLISTT_SMBIOS_TABLES* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_SMBIOS_TABLES>, */* SMBIOS tables for x86 */*
  
  

How about:

BLOBLISTT_LOCAL = 0xf0000000u /* values in this space are for local use during development */

   *BLOBLISTT_COUNT* <https://elixir.bootlin.com/u-boot/latest/source/include/latest/C/ident/BLOBLISTT_COUNT>

};

I would add a BLOBLISTT_UUID for all proprietary things that people want to add. Using private space in a 64 bit field does not make the thing open. So by using this tag, we know exactly the nature of the blob. Negotiating for adding a new tag is a good open governance process.

+1

We may have to deal with super small SRAM (256KB) and thus we can assume the bloblist will be a single region of blobs. So I would add a BLOBLISTT_CONTINUATION which would be a pointer from the SRAM bloblist to a DRAM backed bloblist.

It is possible to relocate a bloblist, so I wonder if another approach would be to allow the bloblist to grow as it progresses through the boot (e.g. once SDRAM is available). That is what U-Boot does and it makes the code simpler (although only very slightly). However, it does introduce copying overhead...?

looks good: just making the problem.

Other tags to consider: PSCI interface details, DRAM information, SCMI stuff, Secure SRAM and DRAM information...

• Going forward we would provide core changes to demonstrate this

design on various TF-A boundries, BL1<->BL2, BL2<->BL31 and BL31<->BL33(only BL31 part)

Please share your thoughts if you disagree to the proposed solution.

Also, refer to attached slide deck which was presented during last tech forum session on 3rd june, it also captures the points discussed during meeting and next steps for implementing it in TF-A.

Re devicetree, how about we use bloblist for simple things, but use a devicetree (perhaps in the bloblist) once SDRAM is available. Blobs that were created pre-SDRAM can continue to be passed on, but anything created after SDRAM is available should use devicetree? This would ensure that complex structures use devicetree rather than C structs, which are of course harder to extend / describe.

+1

Regards,

Simon

Thanks

Manish Pandey

*From:* Joanna Farley Joanna.Farley@arm.com *Sent:* 02 June 2021 16:26 *To:* Madhukar Pappireddy Madhukar.Pappireddy@arm.com; Okash Khawaja < okash.khawaja@gmail.com>; Simon Glass sjg@chromium.org *Cc:* Harb Abdulhamid OS abdulhamid@os.amperecomputing.com; Boot Architecture Mailman List boot-architecture@lists.linaro.org; Ed Stuber edstuber@amperecomputing.com; Arjun Khare akhare@amperecomputing.com; U-Boot Mailing List u-boot@lists.denx.de; Paul Isaac's < paul.isaacs@linaro.org>; Ron Minnich rminnich@google.com; Moe Ammar < moe@amperecomputing.com>; tf-a@lists.trustedfirmware.org < tf-a@lists.trustedfirmware.org>; Manish Pandey2 Manish.Pandey2@arm.com *Subject:* Re: [TF-A] Proposal: TF-A to adopt hand-off blocks (HOBs) for information passing between boot stages

• TF-A list that got dropped (again)!

Joanna

*From: *Joanna Farley Joanna.Farley@arm.com *Date: *Wednesday, 2 June 2021 at 15:29 *To: *Madhukar Pappireddy Madhukar.Pappireddy@arm.com, Okash Khawaja < okash.khawaja@gmail.com>, Simon Glass sjg@chromium.org *Cc: *Harb Abdulhamid OS abdulhamid@os.amperecomputing.com, Boot Architecture Mailman List boot-architecture@lists.linaro.org, Ed Stuber edstuber@amperecomputing.com, Arjun Khare akhare@amperecomputing.com, U-Boot Mailing List u-boot@lists.denx.de, Paul Isaac's < paul.isaacs@linaro.org>, Ron Minnich rminnich@google.com, Moe Ammar < moe@amperecomputing.com> *Subject: *Re: [TF-A] Proposal: TF-A to adopt hand-off blocks (HOBs) for information passing between boot stages

Hi Everyone,

The Manish Pandy and Madhukar Pappireddy of the TF-A team are planning to host another TF-A Tech Forum this Thursday to continue the live discussion.

Here is their agenda:

On tech forum this week, we would like to continue discussions on HOB list design.

The topics which we would like to cover is

1. Evaluate different proposals of passing information through boot phases.

2. If we don't get an agreement on one solution fit for all then we would

try to get consensus for Infra segment platform(to solve original problem mentioned by Harb)

3. Try to get an agreement on size of tags and how "hybrid and tag only"

HOB list can co-exist together?

Details of the call are:

======================

TF-A Tech Forum

When Every 2 weeks from 16:00 to 17:00 on Thursday United Kingdom Time

Calendar tf-a@lists.trustedfirmware.org

Who • Bill Fletcher- creator

• tf-a@lists.trustedfirmware.org

We run an open technical forum call 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 this invite to colleagues. Invites are via the TF-A mailing list and also published on the Trusted Firmware website. Details are here: https://www.trustedfirmware.org/meetings/tf-a-technical-forum/

Trusted Firmware is inviting you to a scheduled Zoom meeting.

Join Zoom Meeting

https://zoom.us/j/9159704974

Meeting ID: 915 970 4974 <(915)%20970-4974>

One tap mobile

+16465588656 <(646)%20558-8656>,,9159704974 <(915)%20970-4974># US (New York)

+16699009128 <(669)%20900-9128>,,9159704974 <(915)%20970-4974># US (San Jose)

Dial by your location

    +1 646 558 8656 <(646)%20558-8656> US (New York)

    +1 669 900 9128 <(669)%20900-9128> US (San Jose)

    877 853 5247 <(877)%20853-5247> US Toll-free

    888 788 0099 <(888)%20788-0099> US Toll-free

Meeting ID: 915 970 4974 <(915)%20970-4974>

Find your local number: https://zoom.us/u/ad27hc6t7h

================

Joanna

On 19/05/2021, 03:50, "Madhukar Pappireddy" Madhukar.Pappireddy@arm.com wrote:

Attached slides presented by Manish in the TF-A tech forum.





-----Original Message-----

From: TF-A <tf-a-bounces@lists.trustedfirmware.org> On Behalf Of

Madhukar Pappireddy via TF-A

Sent: Tuesday, May 18, 2021 8:59 PM

To: Joanna Farley <Joanna.Farley@arm.com>; Okash Khawaja <

okash.khawaja@gmail.com>; Simon Glass sjg@chromium.org

Cc: Harb Abdulhamid OS <abdulhamid@os.amperecomputing.com>; Boot

Architecture Mailman List boot-architecture@lists.linaro.org; Ed Stuber edstuber@amperecomputing.com; Arjun Khare akhare@amperecomputing.com; U-Boot Mailing List u-boot@lists.denx.de; tf-a@lists.trustedfirmware.org; Paul Isaac's paul.isaacs@linaro.org; Ron Minnich rminnich@google.com; Moe Ammar moe@amperecomputing.com

Subject: Re: [TF-A] Proposal: TF-A to adopt hand-off blocks (HOBs) for

information passing between boot stages

Hi,



I tried to summarize the discussions in the previous TF-A tech forum

regarding the proposal to adopt Hand-off Blocks (HOBs) for passing information along the boot chain. I am certain I could not capture all suggestions/concerns brought up during the call. I apologize if I missed and/or misinterpreted any comments and would appreciate it if everyone could share their thoughts in response to this email thread.

The idea is to share information to other boot phases:

> Dynamic information: Created during runtime. Shared in the form of a

chain of blobs(built as a linked list of C structure objects i.e., HOB list).

> Static information: Known at compile time. Historically, shared

through the use of Device Tree/ACPI tables

Both the above requirements are common in many ecosystems and need to

co-exist.

There are broadly 3 problems to solve:

1. Format of HOB structures: It looks like the consensus is that we

could use existing mechanisms for this (BL_AUX_PARAM in TF-A or bloblist in u-boot).

2. Identification of HOB list entries: There is a debate about whether

tags would suffice or if the HOB list producer and consumer would depend on UUID/GUIDs for identifying a specific HOB structure. Another suggestion was to use a hybrid approach. Reserve a single tag ID for identifying/constructing a HOB structure that further leverages UUID based identifier. This way, the generic HOB list doesn't need to support UUIDs and can work with tags.

3. The design contract for the static interface between two boot

phases: The problem at hand is whether to pass a pointer to a HOB list or a device tree blob through the general-purpose registers for configuration hand-off between two boot phases. Some proposals that came up:

        > Proposal 1: Always pass a pointer to the device tree blob

through the GP register and capture the pointer to the HOB list as a property of a node that is uniquely identifiable by the downstream boot phase. This needs to define a device tree binding such that producer and consumer agree on the information passed.

        > Proposal 2: Pass a pointer to a generic container through

the GP register that can be interpreted appropriately by both boot loaders(i.e., producer and consumer of the boot info). This container can either be a dtb or a HOB list which can be simply inferred by checking for a magic header that indicates if the buffer appears to be a flattened device tree.

        > One another concern that was brought up offline is to make

sure we don't break current design contracts between various boot loader phases in TF-A. Many of the general-purpose registers have a designated purpose such as to share configurations between BL images( such as firmware config dtb, SoC config dtb, Non trusted firmware config dtb, memory layout, entry point info, etc.).

If I am not mistaken, a single design may not fit the needs of every

segment(client, Infra, embedded) and the forum is open to solutions tailored for individual segments. Joanna will be sending a follow up email with more information about future TF-A tech forums that serves as a platform for further discussions.

Thanks,

Madhukar



-----Original Message-----

From: TF-A <tf-a-bounces@lists.trustedfirmware.org> On Behalf Of

Joanna Farley via TF-A

Sent: Sunday, May 16, 2021 5:19 AM

To: Okash Khawaja <okash.khawaja@gmail.com>; Simon Glass <

sjg@chromium.org>

Cc: Harb Abdulhamid OS <abdulhamid@os.amperecomputing.com>; Boot

Architecture Mailman List boot-architecture@lists.linaro.org; tf-a@lists.trustedfirmware.org; Ed Stuber edstuber@amperecomputing.com; Arjun Khare akhare@amperecomputing.com; U-Boot Mailing List < u-boot@lists.denx.de>; Paul Isaac's paul.isaacs@linaro.org; Ron Minnich rminnich@google.com; Moe Ammar moe@amperecomputing.com

Subject: Re: [TF-A] Proposal: TF-A to adopt hand-off blocks (HOBs) for

information passing between boot stages

Apologies I failed with the recording. Manish/Madhu will reply early

next week with the slides and some notes to help with a follow up session which we hope to hold this Thursday. Invite and agenda will also be sent out early next week.

Thanks



Joanna



On 14/05/2021, 13:30, "TF-A on behalf of Okash Khawaja via TF-A" <

tf-a-bounces@lists.trustedfirmware.org on behalf of tf-a@lists.trustedfirmware.org> wrote:

   Hi,



    Do we have slides and video from last week's discussion?



    Thanks,

    Okash





    On Wed, May 5, 2021 at 11:52 PM Simon Glass via TF-A

    <tf-a@lists.trustedfirmware.org> wrote:

    >

    > Hi Harb,

    >

    > Thanks for the idea. I am still not completely sure what benefit

UUID provides to an open project. I'd like to propose something different, more in the spirit of open collaboration. I also worry that the word 'standard' seems to be a synonym for UUIDs, UEFI, etc., i.e. enabling/preferring closed-source firmware and the continued decline of open-source projects. It really should not be.

    >

    > So I suggest: Use simple integer IDs and reserve some area for

'private' use. If you want to collaborate across projects outside your company, you either need to allocate a 'public' ID or agree privately between the parties which private ID to use.

    >

    > This means that the default and easiest option is for

collaboration and a public ID, with private ones (whose purpose may be secret) reserved just for private use.

    >

    > Regards,

    > Simon

    >

    > On Wed, 5 May 2021 at 11:42, Harb Abdulhamid OS <

abdulhamid@os.amperecomputing.com> wrote:

    >>

    >> Hey Folks,

    >>

    >> We wanted to put out a middle-ground proposal to help guide the

discussion on the call tomorrow.

    >>

    >>

    >>

    >> A proposal that we have been discussing offline involves

reserving a single tag ID for the purpose of construction UEFI PI HOB List structure, and that tag would be used to identify a HOB-specific structure that does leverage UUID based identifier. This will eliminate the burden of having to support UUID as the tag, and this enables projects that require UUID based identifiers for the broad range of HOB structures that need to be produced during the booting of the platform. Once we have a tag for a HOB list, this will enable various HOB producers that can add/extend the HOB list in TF-A code (or even pre-TF-A code), with a HOB consumer for that UUID/GUID on the other side (i.e. whatever the BL33 image is booting on that platform).

    >>

    >>

    >>

    >> Essentially, the idea is if someone would like to support HOB

structures in a standard way using TF-A, they would wrap it up in a BL_AUX_PARAM/BLOB structure (whatever the group decides) and the way we identify the structure as a HOB list is with this new reserved tag.

    >>

    >>

    >>

    >> Hopefully that makes sense and less contentious.  Look forward

to discuss this further on the call.

    >>

    >>

    >>

    >> Thanks,

    >>

    >> --Harb

    >>

    >>

    >>

    >> From: Manish Pandey2 <Manish.Pandey2@arm.com>

    >> Sent: Friday, April 30, 2021 8:14 AM

    >> To: François Ozog <francois.ozog@linaro.org>

    >> Cc: Simon Glass <sjg@chromium.org>; Julius Werner <

jwerner@chromium.org>; Harb Abdulhamid OS < abdulhamid@os.amperecomputing.com>; Boot Architecture Mailman List < boot-architecture@lists.linaro.org>; tf-a@lists.trustedfirmware.org; U-Boot Mailing List u-boot@lists.denx.de; Paul Isaac's < paul.isaacs@linaro.org>; Ron Minnich rminnich@google.com

    >> Subject: Re: [TF-A] Proposal: TF-A to adopt hand-off blocks

(HOBs) for information passing between boot stages

    >>

    >>

    >>

    >> Hi All,

    >>

    >>

    >>

    >> Please find invite for next TF-A Tech Forum session to continue

our discussions on HOB implementation, feel free to forward it to others.

    >>

    >>

    >>

    >> The next TF-A Tech Forum is scheduled for Thu 6th May 2021

16:00 – 17:00 (BST).

    >>

    >>

    >>

    >> Agenda:

    >>

    >> Discussion Session: Static and Dynamic Information Handling in

TF-A

    >>

    >> Lead by Manish Pandey and Madhukar Pappireddy

    >>

    >> ·         There is ongoing mailing lists discussion[1] related

with adopting a mechanism to pass information through boot stages.

    >>

    >> The requirement is two-fold:

    >>

    >> 1.      Passing static information(config files)

    >>

    >> 2.      Passing dynamic information (Hob list)

    >>

    >> In the upcoming TF-A tech forum, we can start with a discussion

on dynamic information passing and if time permits, we can cover static information passing. The purpose of the call is to have an open discussion and continue the discussion from the trusted-substrate call[2] done earlier. We would like to understand the various requirements and possible ways to implement it in TF-A in a generalized way so that it can work with other Firmware projects.

    >>

    >>

    >>

    >> The two specific item which we would like to discuss are:

    >>

    >> 1.      HOB format: TF-A/u-boot both has an existing bloblist

implementation, which uses tag values. Question, can this be enhanced to use hybrid values(Tag and UUID) both?

    >>

    >> 2.      Standardization on Physical register use to pass base

of HoB data structure.

    >>

    >> References:

    >>

    >> [1]

https://lists.trustedfirmware.org/pipermail/tf-a/2021-April/001069.html

    >>

    >> [2]

https://linaro-org.zoom.us/rec/share/zjfHeMIumkJhirLCVQYTHR6ftaqyWvF_0klgQnH... Passcode: IPn+5q%

    >>

    >>

    >>

    >> Thanks

    >>

    >>

    >>

    >> Joanna

    >>

    >>

    >>

    >> You have been invited to the following event.

    >>

    >> TF-A Tech Forum

    >>

    >> When

    >>

    >> Every 2 weeks from 16:00 to 17:00 on Thursday United Kingdom

Time

    >>

    >> Calendar

    >>

    >> tf-a@lists.trustedfirmware.org

    >>

    >> Who

    >>

    >> •

    >>

    >> Bill Fletcher- creator

    >>

    >> •

    >>

    >> tf-a@lists.trustedfirmware.org

    >>

    >> more details »

    >>

    >>

    >>

    >> We run an open technical forum call 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 this invite to colleagues. Invites are via

the TF-A mailing list and also published on the Trusted Firmware website. Details are here: https://www.trustedfirmware.org/meetings/tf-a-technical-forum/

    >>

    >>

    >>

    >> Trusted Firmware is inviting you to a scheduled Zoom meeting.

    >>

    >>

    >>

    >> Join Zoom Meeting

    >>

    >> https://zoom.us/j/9159704974

    >>

    >>

    >>

    >> Meeting ID: 915 970 4974 <(915)%20970-4974>

    >>

    >>

    >>

    >> One tap mobile

    >>

    >> +16465588656 <(646)%20558-8656>,,9159704974 <(915)%20970-4974>#

US (New York)

    >>

    >> +16699009128 <(669)%20900-9128>,,9159704974 <(915)%20970-4974>#

US (San Jose)

    >>

    >>

    >>

    >> Dial by your location

    >>

    >>         +1 646 558 8656 <(646)%20558-8656> US (New York)

    >>

    >>         +1 669 900 9128 <(669)%20900-9128> US (San Jose)

    >>

    >>         877 853 5247 <(877)%20853-5247> US Toll-free

    >>

    >>         888 788 0099 <(888)%20788-0099> US Toll-free

    >>

    >> Meeting ID: 915 970 4974 <(915)%20970-4974>

    >>

    >> Find your local number: https://zoom.us/u/ad27hc6t7h

    >>

    >>

    >>

    >> ________________________________

    >>

    >> From: François Ozog <francois.ozog@linaro.org>

    >> Sent: 08 April 2021 16:50

    >> To: Manish Pandey2 <Manish.Pandey2@arm.com>

    >> Cc: Simon Glass <sjg@chromium.org>; Julius Werner <

jwerner@chromium.org>; Harb Abdulhamid OS < abdulhamid@os.amperecomputing.com>; Boot Architecture Mailman List < boot-architecture@lists.linaro.org>; tf-a@lists.trustedfirmware.org < tf-a@lists.trustedfirmware.org>; U-Boot Mailing List u-boot@lists.denx.de; Paul Isaac's paul.isaacs@linaro.org; Ron Minnich rminnich@google.com

    >> Subject: Re: [TF-A] Proposal: TF-A to adopt hand-off blocks

(HOBs) for information passing between boot stages

    >>

    >>

    >>

    >> Hi

    >>

    >>

    >>

    >> here is the meeting recording:

    >>

    >>

https://linaro-org.zoom.us/rec/share/zjfHeMIumkJhirLCVQYTHR6ftaqyWvF_0klgQnH... Passcode: IPn+5q%z

    >>

    >>

    >>

    >> I am really sorry about the confusion related to the meeting

time. I have now understood: the Collaborate portal uses a specific calendar which is tied to US/Chicago timezone while the actual Google Calendar is tied to Central Europe timezone. I am going to drop the Collaborate portal and use a shared Google calendar (it should be visible on the trusted-substrate.org page).

    >>

    >>

    >>

    >> I'll try to summarize what I learnt and highlight my view on

what can be next steps in a future mail.

    >>

    >>

    >>

    >> Cheers

    >>

    >>

    >>

    >> FF

    >>

    >>

    >>

    >> On Thu, 8 Apr 2021 at 13:56, Manish Pandey2 via TF-A <

tf-a@lists.trustedfirmware.org> wrote:

    >>

    >> Hi,

    >>

    >>

    >>

    >> From TF-A project point of view, we prefer to use existing

mechanism to pass parameters across boot stages using linked list of tagged elements (as suggested by Julius). It has support for both generic and SiP-specific tags. Having said that, it does not stop partners to introduce new mechanisms suitable for their usecase in platform port initially and later move to generic code if its suitable for other platforms.

    >>

    >>

    >>

    >> To start with, Ampere can introduce a platform specific

implementation of memory tag(speed/NUMA topology etc) which can be evaluated and discussed for generalization in future. The tag will be populated in BL2 stage and can be forwarded to further stages(and to BL33) by passing the head of list pointer in one of the registers. Initially any register can be used but going forward a standardization will be needed.

    >>

    >>

    >>

    >> The U-boot bloblist mentioned by Simon is conceptually similar

to what TF-A is using, if there is consensus of using bloblist/taglist then TF-A tag list may be enhanced to take best of both the implementations.

    >>

    >>

    >>

    >> One of the potential problems of having structure used in

different projects is maintainability, this can be avoided by having a single copy of these structures in TF-A (kept inside "include/export" which intended to be used by other projects.)

    >>

    >>

    >>

    >> Regarding usage of either UUID or tag, I echo the sentiments of

Simon and Julius to keep it simple and use tag values.

    >>

    >>

    >>

    >> Looking forward to having further discussions on zoom call

today.

    >>

    >>

    >>

    >> Thanks

    >>

    >> Manish P

    >>

    >>

    >>

    >> ________________________________

    >>

    >> From: TF-A <tf-a-bounces@lists.trustedfirmware.org> on behalf

of Julius Werner via TF-A tf-a@lists.trustedfirmware.org

    >> Sent: 25 March 2021 02:43

    >> To: Simon Glass <sjg@chromium.org>

    >> Cc: Harb Abdulhamid OS <abdulhamid@os.amperecomputing.com>;

Boot Architecture Mailman List boot-architecture@lists.linaro.org; tf-a@lists.trustedfirmware.org tf-a@lists.trustedfirmware.org; U-Boot Mailing List u-boot@lists.denx.de; Paul Isaac's paul.isaacs@linaro.org; Ron Minnich rminnich@google.com

    >> Subject: Re: [TF-A] Proposal: TF-A to adopt hand-off blocks

(HOBs) for information passing between boot stages

    >>

    >>

    >>

    >> Just want to point out that TF-A currently already supports a

(very simple) mechanism like this:

    >>

    >>

    >>

    >>

https://review.trustedfirmware.org/plugins/gitiles/TF-A/trusted-firmware-a/+...

    >>

    >>

https://review.trustedfirmware.org/plugins/gitiles/TF-A/trusted-firmware-a/+...

    >>

    >>

https://review.trustedfirmware.org/plugins/gitiles/TF-A/trusted-firmware-a/+...

    >>

    >>

    >>

    >> It's just a linked list of tagged elements. The tag space is

split into TF-A-wide generic tags and SiP-specific tags (with plenty of room to spare if more areas need to be defined -- a 64-bit tag can fit a lot). This is currently being used by some platforms that run coreboot in place of BL1/BL2, to pass information from coreboot (BL2) to BL31.

    >>

    >>

    >>

    >> I would echo Simon's sentiment of keeping this as simple as

possible and avoiding complicated and bloated data structures with UUIDs. You usually want to parse something like this as early as possible in the passed-to firmware stage, particularly if the structure encodes information about the debug console (like it does for the platforms I mentioned above). For example, in BL31 this basically means doing it right after moving from assembly to C in bl31_early_platform_setup2() to get the console up before running anything else. At that point in the BL31 initialization, the MMU and caches are disabled, so data accesses are pretty expensive and you don't want to spend a lot of parsing effort or calculate complicated checksums or the like. You just want something extremely simple where you ideally have to touch every data word only once.

    >>

    >>

    >>

    >> On Wed, Mar 24, 2021 at 5:06 PM Simon Glass via TF-A <

tf-a@lists.trustedfirmware.org> wrote:

    >>

    >> Hi Harb,

    >>

    >>

    >>

    >> On Wed, 24 Mar 2021 at 11:39, Harb Abdulhamid OS <

abdulhamid@os.amperecomputing.com> wrote:

    >>

    >> Hello Folks,

    >>

    >> Appreciate the feedback and replies on this.  Glad to see that

there is interest in this topic.

    >>

    >>

    >>

    >> I try to address the comments/feedback from Francois and Simon

below….

    >>

    >>

    >>

    >> @François Ozog – happy to discuss this on a zoom call.  I will

make that time slot work, and will be available to attend April 8, 4pm CT.

    >>

    >>

    >>

    >> Note that I’m using the term “HOB” here more generically, as

there are typically vendor specific structures beyond the resource descriptor HOB, which provides only a small subset of the information that needs to be passed between the boot phases.

    >>

    >>

    >>

    >> The whole point here is to provide mechanism to develop

firmware that we can build ARM Server SoC’s that support *any* BL33 payload (e.g. EDK2, AptioV, CoreBoot, and maybe even directly boot strapping LinuxBoot at some point). In other-words, we are trying to come up with a TF-A that would be completely agnostic to the implementation of BL33 (i.e. BL33 is built completely independently by a separate entity – e.g. an ODM/OEM).

    >>

    >>

    >>

    >> Keep in mind, in the server/datacenter market segment we are

not building vertically integrated systems with a single entity compiling firmware/software stacks like most folks in TF-A have become use to. There are two categories of higher level firmware code blobs in the server/datacenter model:

    >>

    >> “SoC” or “silicon” firmware – in TF-A this may map to BL1, BL2,

BL31, and *possibly* one or more BL32 instances

    >> “Platform” or “board” firmware – in TF-A this may map to BL33

and *possibly* one or more BL32 instances.

    >>

    >>

    >>

    >> Even the platform firmware stack could be further fragmented by

having multiple entities involved in delivering the entire firmware stack: IBVs, ODMs, OEMs, CSPs, and possibly even device vendor code.

    >>

    >>

    >>

    >> To support a broad range of platform designs with a broad range

of memory devices, we need a crisp and clear contract between the SoC firmware that initializes memory (e.g. BL2) and how that platform boot firmware (e.g. BL33) gathers information about what memory that was initialized, at what speeds, NUMA topology, and many other relevant information that needs to be known and comprehended by the platform firmware and eventually by the platform software.

    >>

    >>

    >>

    >> I understand the versatility of DT, but I see two major

problems with DT:

    >>

    >> DT requires more complicated parsing to get properties, and

even more complex to dynamically set properties – this HOB structures may need to be generated in boot phases where DDR is not available, and therefore we will be extremely memory constrained.

    >> DT is probably overkill for this purpose – We really just want

a list of pointers to simple C structures that code cast (e.g. JEDEC SPD data blob)

    >>

    >>

    >>

    >> I think that we should not mix the efforts around DT/ACPI specs

with what we are doing here, because those specs and concepts were developed for a completely different purpose (i.e. abstractions needed for OS / RTOS software, and not necessarily suitable for firmware-to-firmware hand-offs).

    >>

    >>

    >>

    >> Frankly, I would personally push back pretty hard on defining

SMC’s for something that should be one way information passing. Every SMC we add is another attack vector to the secure world and an increased burden on the folks that have to do security auditing and threat analysis. I see no benefit in exposing these boot/HOB/BOB structures at run-time via SMC calls.

    >>

    >>

    >>

    >> Please do let me know if you disagree and why.  Look forward to

discussing on this thread or on the call.

    >>

    >>

    >>

    >> @Simon Glass   - Thanks for the pointer to bloblist.   I

briefly reviewed and it seems like a goo

--

*François-Frédéric Ozog* | *Director Linaro Edge & Fog Computing Group*

T: +33.67221.6485 francois.ozog@linaro.org | Skype: ffozog