Hi,
My interest in boot information passing is from the perspective of a
down-boot-chain consumer. From this perspective, I have the following
preferences:
1) Whatever information passing mechanism is used (e.g. HOB or DT), we use a
common object identification scheme that may be used with either mechanism.
This helps to decouple components that consume information from the actual
delivery method.
2) A hierarchical naming scheme is used (e.g. like the DT 'compatible' string).
This has the following benefits:
a. Scales well as the naming authority can be delegated to different
organisations.
b. Clear traceability to the defining authority.
c. No reliance on a central register of IDs.
d. New IDs can be freely defined without much ceremony.
e. Names can be meaningful and easy to understand.
f. The hierarchical structure may be exploited if necessary to include
things like family, version, instance number or any other structure that makes
sense to the naming authority.
Just my two cents worth.
Best regards,
Julian
-----Original Message-----
From: TF-A <[email protected]> On Behalf Of Madhukar
Pappireddy via TF-A
Sent: 19 May 2021 02:59
To: Joanna Farley <[email protected]>; Okash Khawaja
<[email protected]>; Simon Glass <[email protected]>
Cc: Harb Abdulhamid OS <[email protected]>; Boot Architecture
Mailman List <[email protected]>; Ed Stuber
<[email protected]>; Arjun Khare <[email protected]>;
U-Boot Mailing List <[email protected]>; [email protected];
Paul Isaac's <[email protected]>; Ron Minnich <[email protected]>; Moe
Ammar <[email protected]>
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 <[email protected]> On Behalf Of Joanna Farley
via TF-A
Sent: Sunday, May 16, 2021 5:19 AM
To: Okash Khawaja <[email protected]>; Simon Glass <[email protected]>
Cc: Harb Abdulhamid OS <[email protected]>; Boot Architecture
Mailman List <[email protected]>;
[email protected]; Ed Stuber <[email protected]>; Arjun
Khare <[email protected]>; U-Boot Mailing List <[email protected]>;
Paul Isaac's <[email protected]>; Ron Minnich <[email protected]>; Moe
Ammar <[email protected]>
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"
<[email protected] on behalf of
[email protected]> 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
<[email protected]> 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
<[email protected]> 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 <[email protected]>
>> Sent: Friday, April 30, 2021 8:14 AM
>> To: François Ozog <[email protected]>
>> Cc: Simon Glass <[email protected]>; Julius Werner
<[email protected]>; Harb Abdulhamid OS <[email protected]>;
Boot Architecture Mailman List <[email protected]>;
[email protected]; U-Boot Mailing List <[email protected]>;
Paul Isaac's <[email protected]>; Ron Minnich <[email protected]>
>> 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_0klgQnHTqzgA5Wav0qOO8n7SAM0yj-Hg.mLyFkVJNB1vDKqw_
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
>>
>> [email protected]
>>
>> Who
>>
>> •
>>
>> Bill Fletcher- creator
>>
>> •
>>
>> [email protected]
>>
>> 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
>>
>>
>>
>> One 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-free
>>
>> Meeting ID: 915 970 4974
>>
>> Find your local number: https://zoom.us/u/ad27hc6t7h
>>
>>
>>
>> ________________________________
>>
>> From: François Ozog <[email protected]>
>> Sent: 08 April 2021 16:50
>> To: Manish Pandey2 <[email protected]>
>> Cc: Simon Glass <[email protected]>; Julius Werner
<[email protected]>; Harb Abdulhamid OS <[email protected]>;
Boot Architecture Mailman List <[email protected]>;
[email protected] <[email protected]>; U-Boot Mailing
List <[email protected]>; Paul Isaac's <[email protected]>; Ron Minnich
<[email protected]>
>> 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_0klgQnHTqzgA5Wav0qOO8n7SAM0yj-Hg.mLyFkVJNB1vDKqw_
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
<[email protected]> 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 <[email protected]> on behalf of Julius
Werner via TF-A <[email protected]>
>> Sent: 25 March 2021 02:43
>> To: Simon Glass <[email protected]>
>> Cc: Harb Abdulhamid OS <[email protected]>; Boot
Architecture Mailman List <[email protected]>;
[email protected] <[email protected]>; U-Boot Mailing
List <[email protected]>; Paul Isaac's <[email protected]>; Ron Minnich
<[email protected]>
>> 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/+/refs/heads/master/include/export/lib/bl_aux_params/bl_aux_params_exp.h
>>
>>
https://review.trustedfirmware.org/plugins/gitiles/TF-A/trusted-firmware-a/+/refs/heads/master/lib/bl_aux_params/bl_aux_params.c
>>
>>
https://review.trustedfirmware.org/plugins/gitiles/TF-A/trusted-firmware-a/+/refs/heads/master/plat/rockchip/common/params_setup.c
>>
>>
>>
>> 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
<[email protected]> wrote:
>>
>> Hi Harb,
>>
>>
>>
>> On Wed, 24 Mar 2021 at 11:39, Harb Abdulhamid OS
<[email protected]> 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 good baseline for what we may be looking for.
>>
>>
>>
>> That being said, I would say that there is some benefit in having some
kind of unique identifiers (e.g. UUID or some unique signature) so that we can
tie standardized data structures (based on some future TBD specs) to a
particular ID. For example, if the TPM driver in BL33 is looking for the TPM
structure in the HOB/BOB list, and may not care about the other data blobs.
The driver needs a way to identify and locate the blob it cares about.
>>
>>
>>
>> The tag is intended to serve that purpose, although perhaps it should
switch from an auto-allocating enum to one with explicit values for each entry
and a range for 'local' use.
>>
>>
>>
>> I guess we can achieve this with the tag, but the problem with tag when
you have eco-system with a lot of parties doing parallel development, you can
end up with tag collisions and folks fighting about who has rights to what tag
values. We would need some official process for folks to register tags for
whatever new structures we define, or maybe some tag range for vendor specific
structures. This comes with a lot of pain and bureaucracy. On the other hand,
UUID has been a proven way to make it easy to just define your own blobs with
*either* standard or vendor specific structures without worry of ID collisions
between vendors.
>>
>>
>>
>> True. I think the pain is overstated, though. In this case I think we
actually want something that can be shared between projects and orgs, so some
amount of coordination could be considered a benefit. It could just be a github
pull request. I find the UUID unfriendly and not just to code size and
eyesight! Trying to discover what GUIDs mean or are valid is quite tricky. E.g.
see this code:
>>
>>
>>
>> #define FSP_HOB_RESOURCE_OWNER_TSEG_GUID \
>> EFI_GUID(0xd038747c, 0xd00c, 0x4980, \
>> 0xb3, 0x19, 0x49, 0x01, 0x99, 0xa4, 0x7d, 0x55)
>>
>> (etc.)
>>
>>
>>
>> static struct guid_name {
>> efi_guid_t guid;
>> const char *name;
>> } guid_name[] = {
>> { FSP_HOB_RESOURCE_OWNER_TSEG_GUID, "TSEG" },
>> { FSP_HOB_RESOURCE_OWNER_FSP_GUID, "FSP" },
>> { FSP_HOB_RESOURCE_OWNER_SMM_PEI_SMRAM_GUID, "SMM PEI SMRAM" },
>> { FSP_NON_VOLATILE_STORAGE_HOB_GUID, "NVS" },
>> { FSP_VARIABLE_NV_DATA_HOB_GUID, "Variable NVS" },
>> { FSP_GRAPHICS_INFO_HOB_GUID, "Graphics info" },
>> { FSP_HOB_RESOURCE_OWNER_PCD_DATABASE_GUID1, "PCD database ea" },
>> { FSP_HOB_RESOURCE_OWNER_PCD_DATABASE_GUID2, "PCD database 9b" },
>>
>> (never figured out what those two are)
>>
>>
>> { FSP_HOB_RESOURCE_OWNER_PEIM_DXE_GUID, "PEIM Init DXE" },
>> { FSP_HOB_RESOURCE_OWNER_ALLOC_STACK_GUID, "Alloc stack" },
>> { FSP_HOB_RESOURCE_OWNER_SMBIOS_MEMORY_GUID, "SMBIOS memory" },
>> { {}, "zero-guid" },
>> {}
>> };
>>
>> static const char *guid_to_name(const efi_guid_t *guid)
>> {
>> struct guid_name *entry;
>>
>> for (entry = guid_name; entry->name; entry++) {
>> if (!guidcmp(guid, &entry->guid))
>> return entry->name;
>> }
>>
>> return NULL;
>> }
>>
>>
>>
>> Believe it or not it took a fair bit of effort to find just that small
list, with nearly every one in a separate doc, from memory.
>>
>>
>>
>>
>>
>> We can probably debate whether there is any value in GUID/UUID or not
during the call… but again, boblist seems like a reasonable starting point as
an alternative to HOB.
>>
>>
>>
>> Indeed. There is certainly value in both approaches.
>>
>>
>>
>> Regards,
>>
>> Simon
>>
>>
>>
>>
>>
>> Thanks,
>>
>> --Harb
>>
>>
>>
>> From: François Ozog <[email protected]>
>> Sent: Tuesday, March 23, 2021 10:00 AM
>> To: François Ozog <[email protected]>; Ron Minnich
<[email protected]>; Paul Isaac's <[email protected]>
>> Cc: Simon Glass <[email protected]>; Harb Abdulhamid OS
<[email protected]>; Boot Architecture Mailman List
<[email protected]>; [email protected]
>> Subject: Re: [TF-A] Proposal: TF-A to adopt hand-off blocks (HOBs) for
information passing between boot stages
>>
>>
>>
>> +Ron Minnich +Paul Isaac's
>>
>>
>>
>> Adding Ron and Paul because I think this interface should be also
benefiting LinuxBoot efforts.
>>
>>
>>
>> On Tue, 23 Mar 2021 at 11:17, François Ozog via TF-A
<[email protected]> wrote:
>>
>> Hi,
>>
>>
>>
>> I propose we cover the topic at the next Trusted Substrate zoom call
on April 8th 4pm CET.
>>
>>
>>
>> The agenda:
>>
>> ABI between non-secure firmware and the rest of firmware (EL3, S-EL1,
S-EL2, SCP) to adapt hardware description to some runtime conditions.
>>
>> runtime conditions here relates to DRAM size and topology detection,
secure DRAM memory carvings, PSCI and SCMI interface publishing.
>>
>>
>>
>> For additional background on existing metadata: UEFI Platform
Initialization Specification Version 1.7, 5.5 Resource Descriptor HOB
>>
>> Out of the ResourceType we care about is EFI_RESOURCE_SYSTEM_MEMORY.
>>
>> This HOB lacks memory NUMA attachment or something that could be related
to fill SRAT table for ACPI or relevant DT proximity domains.
>>
>> HOB is not consistent accros platforms: some platforms (Arm) lists
memory from the booting NUMA node, other platforms (x86) lists all memory from
all NUMA nodes. (At least this is the case on the two platforms I tested).
>>
>>
>>
>> There are two proposals to use memory structures from SPL/BLx up to the
handover function (as defined in the Device Tree technical report) which can be
U-boot (BL33 or just U-Boot in case of SPL/U-Boot scheme) or EDK2.
>>
>> I would propose we also discuss possibility of FF-A interface to
actually query information or request actions to be done (this is a model
actually used in some SoCs with proprietary SMC calls).
>>
>>
>>
>> Requirements (to be validated):
>>
>> - ACPI and DT hardware descriptions.
>>
>> - agnostic to boot framework (SPL/U-Boot, TF-A/U-Boot, TF-A/EDK2)
>>
>> - agnostic to boot framework (SPL/U-Boot, TF-A/U-Boot, TF-A/EDK2,
TF-A/LinuxBoot)
>>
>> - at least allows complete DRAM description and "persistent" usage
(reserved areas for secure world or other usages)
>>
>> - support secure world device assignment
>>
>>
>>
>> Cheers
>>
>>
>>
>> FF
>>
>>
>>
>>
>>
>> On Mon, 22 Mar 2021 at 19:56, Simon Glass <[email protected]> wrote:
>>
>> Hi,
>>
>> Can I suggest using bloblist for this instead? It is lightweight,
>> easier to parse, doesn't have GUIDs and is already used within U-Boot
>> for passing info between SPL/U-Boot, etc.
>>
>> Docs here:
https://github.com/u-boot/u-boot/blob/master/doc/README.bloblist
>> Header file describes the format:
>> https://github.com/u-boot/u-boot/blob/master/include/bloblist.h
>>
>> Full set of unit tests:
>> https://github.com/u-boot/u-boot/blob/master/test/bloblist.c
>>
>> Regards,
>> Simon
>>
>> On Mon, 22 Mar 2021 at 23:58, François Ozog <[email protected]>
wrote:
>> >
>> > +Boot Architecture Mailman List <[email protected]>
>> >
>> > standardization is very much welcomed here and need to accommodate a
very
>> > diverse set of situations.
>> > For example, TEE OS may need to pass memory reservations to BL33 or
>> > "capture" a device for the secure world.
>> >
>> > I have observed a number of architectures:
>> > 1) pass information from BLx to BLy in the form of a specific object
>> > 2) BLx called by BLy by a platform specific SMC to get information
>> > 3) BLx called by BLy by a platform specific SMC to perform Device Tree
>> > fixups
>> >
>> > I also imagined a standardized "broadcast" FF-A call so that any
firmware
>> > element can either provide information or "do something".
>> >
>> > My understanding of your proposal is about standardizing on
architecture 1)
>> > with the HOB format.
>> >
>> > The advantage of the HOB is simplicity but it may be difficult to
implement
>> > schemes such as pruning a DT because device assignment in the secure
world.
>> >
>> > In any case, it looks feasible to have TF-A and OP-TEE complement the
list
>> > of HOBs to pass information downstream (the bootflow).
>> >
>> > It would be good to start with building the comprehensive list of
>> > information that need to be conveyed between firmware elements:
>> >
>> > information. | authoritative entity | reporting entity | information
>> > exchanged:
>> > dram | TFA | TFA
|
>> > <format to be detailed, NUMA topology to build the SRAT table or DT
>> > equivalent?>
>> > PSCI | SCP | TFA? |
>> > SCMI | SCP or TEE-OS | TFA? TEE-OS?|
>> > secure SRAM | TFA. | TFA. |
>> > secure DRAM | TFA? TEE-OS? | TFA? TEE-OS? |
>> > other? | |
>> > |
>> >
>> > Cheers
>> >
>> > FF
>> >
>> >
>> > On Mon, 22 Mar 2021 at 09:34, Harb Abdulhamid OS via TF-A <
>> > [email protected]> wrote:
>> >
>> > > Hello Folks,
>> > >
>> > >
>> > >
>> > > I'm emailing to start an open discussion about the adoption of a
concept
>> > > known as "hand-off blocks" or HOB to become a part of the TF-A
Firmware
>> > > Framework Architecture (FFA). This is something that is a pretty
major
>> > > pain point when it comes to the adoption of TF-A in ARM Server SoC’s
>> > > designed to enable a broad range of highly configurable datacenter
>> > > platforms.
>> > >
>> > >
>> > >
>> > >
>> > >
>> > > What is a HOB (Background)?
>> > >
>> > > ---------------------------
>> > >
>> > > UEFI PI spec describes a particular definition for how HOB may be
used for
>> > > transitioning between the PEI and DXE boot phases, which is a good
>> > > reference point for this discussion, but not necessarily the exact
solution
>> > > appropriate for TF-A.
>> > >
>> > >
>> > >
>> > > A HOB is simply a dynamically generated data structure passed in
between
>> > > two boot phases. This is information that was obtained through
discovery
>> > > and needs to be passed forward to the next boot phase *once*, with
no API
>> > > needed to call back (e.g. no call back into previous firmware phase
is
>> > > needed to fetch this information at run-time - it is simply passed
one time
>> > > during boot).
>> > >
>> > >
>> > >
>> > > There may be one or more HOBs passed in between boot phases. If
there are
>> > > more than one HOB that needs to be passed, this can be in a form of
a "HOB
>> > > table", which (for example) could be a UUID indexed array of
pointers to
>> > > HOB structures, used to locate a HOB of interest (based on UUID).
In such
>> > > cases, instead of passing a single HOB, the boot phases may rely on
passing
>> > > the pointer to the HOB table.
>> > >
>> > >
>> > >
>> > > This has been extremely useful concept to employ on highly
configurable
>> > > systems that must rely on flexible discovery mechanisms to
initialize and
>> > > boot the system. This is especially helpful when you have multiple
>> > >
>> > >
>> > >
>> > >
>> > >
>> > > Why do we need HOBs in TF-A?:
>> > >
>> > > -----------------------------
>> > >
>> > > It is desirable that EL3 firmware (e.g. TF-A) built for ARM Server
SoC in
>> > > a way that is SoC specific *but* platform agnostic. This means that
a
>> > > single ARM SoC that a SiP may deliver to customers may provide a
single
>> > > TF-A binary (e.g. BL1, BL2, BL31) that could be used to support a
broad
>> > > range of platform designs and configurations in order to boot a
platform
>> > > specific firmware (e.g. BL33 and possibly even BL32 code). In order
to
>> > > achieve this, the platform configuration must be *discovered*
instead of
>> > > statically compiled as it is today in TF-A via device tree based
>> > > enumeration. The mechanisms of discovery may differ broadly
depending on
>> > > the relevant industry standard, or in some cases may have rely on SiP
>> > > specific discovery flows.
>> > >
>> > >
>> > >
>> > > For example: On server systems that support a broad range DIMM
memory
>> > > population/topologies, all the necessary information required to
boot is
>> > > fully discovered via standard JEDEC Serial Presence Detect (SPD)
over an
>> > > I2C bus. Leveraging the SPD bus, may platform variants could be
supported
>> > > with a single TF-A binary. Not only is this information required to
>> > > initialize memory in early boot phases (e.g. BL2), the subsequent
boot
>> > > phases will also need this SPD info to construct a system physical
address
>> > > map and properly initialize the MMU based on the memory present, and
where
>> > > the memory may be present. Subsequent boot phases (e.g. BL33 /
UEFI) may
>> > > need to generate standard firmware tables to the operating systems,
such as
>> > > SMBIOS tables describing DIMM topology and various ACPI tables (e.g.
SLIT,
>> > > SRAT, even NFIT if NVDIMM's are present).
>> > >
>> > >
>> > >
>> > > In short, it all starts with a standardized or vendor specific
discovery
>> > > flow in an early boot stage (e.g. BL1/BL2), followed by the passing
of
>> > > information to the next boot stages (e.g. BL31/BL32/BL33).
>> > >
>> > >
>> > >
>> > > Today, every HOB may be a vendor specific structure, but in the
future
>> > > there may be benefit of defining standard HOBs. This may be useful
for
>> > > memory discovery, passing the system physical address map, enabling
TPM
>> > > measured boot, and potentially many other common HOB use-cases.
>> > >
>> > >
>> > >
>> > > It would be extremely beneficial to the datacenter market segment if
the
>> > > TF-A community would adopt this concept of information passing
between all
>> > > boot phases as opposed to rely solely on device tree enumeration.
This is
>> > > not intended to replace device tree, rather intended as an
alternative way
>> > > to describe the info that must be discovered and dynamically
generated.
>> > >
>> > >
>> > >
>> > >
>> > >
>> > > Conclusion:
>> > >
>> > > -----------
>> > >
>> > > We are proposing that the TF-A community begin pursuing the adoption
of
>> > > HOBs as a mechanism used for information exchange between each boot
stage
>> > > (e.g. BL1->BL2, BL2->BL31, BL31->BL32, and BL31->BL33)? Longer term
we
>> > > want to explore standardizing some HOB structures for the BL33 phase
(e.g.
>> > > UEFI HOB structures), but initially would like to agree on this
being a
>> > > useful mechanism used to pass information between each boot stage.
>> > >
>> > >
>> > >
>> > > Thanks,
>> > >
>> > > --Harb
>> > >
>> > >
>> > >
>> > >
>> > >
>> > >
>> > > --
>> > > TF-A mailing list
>> > > [email protected]
>> > > https://lists.trustedfirmware.org/mailman/listinfo/tf-a
>> > >
>> >
>> >
>> > --
>> > François-Frédéric Ozog | *Director Linaro Edge & Fog Computing Group*
>> > T: +33.67221.6485
>> > [email protected] | Skype: ffozog
>> > _______________________________________________
>> > boot-architecture mailing list
>> > [email protected]
>> > https://lists.linaro.org/mailman/listinfo/boot-architecture
>>
>>
>>
>>
>> --
>>
>> François-Frédéric Ozog | Director Linaro Edge & Fog Computing Group
>>
>> T: +33.67221.6485
>> [email protected] | Skype: ffozog
>>
>>
>>
>> --
>> TF-A mailing list
>> [email protected]
>> https://lists.trustedfirmware.org/mailman/listinfo/tf-a
>>
>>
>>
>>
>> --
>>
>> François-Frédéric Ozog | Director Linaro Edge & Fog Computing Group
>>
>> T: +33.67221.6485
>> [email protected] | Skype: ffozog
>>
>>
>>
>> --
>> TF-A mailing list
>> [email protected]
>> https://lists.trustedfirmware.org/mailman/listinfo/tf-a
>>
>> --
>> TF-A mailing list
>> [email protected]
>> https://lists.trustedfirmware.org/mailman/listinfo/tf-a
>>
>>
>>
>>
>> --
>>
>> François-Frédéric Ozog | Director Linaro Edge & Fog Computing Group
>>
>> T: +33.67221.6485
>> [email protected] | Skype: ffozog
>>
>>
>
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