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 <francois.o...@linaro.org> wrote: > > +Boot Architecture Mailman List <boot-architecture@lists.linaro.org> > > 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 < > t...@lists.trustedfirmware.org> 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 > > t...@lists.trustedfirmware.org > > https://lists.trustedfirmware.org/mailman/listinfo/tf-a > > > > > -- > François-Frédéric Ozog | *Director Linaro Edge & Fog Computing Group* > T: +33.67221.6485 > francois.o...@linaro.org | Skype: ffozog > _______________________________________________ > boot-architecture mailing list > boot-architecture@lists.linaro.org > https://lists.linaro.org/mailman/listinfo/boot-architecture _______________________________________________ boot-architecture mailing list boot-architecture@lists.linaro.org https://lists.linaro.org/mailman/listinfo/boot-architecture
