core: add HOB creation and Apply FF-A v1.2 in stmm_sp.

[LeviYeoReum]

According to Platform Initialization (PI) Specification [1] and
Discussion on edk2 mailing list [2],
StandaloneMm shouldn't create Hob but it should be passed from TF-A.
That's why StandaloneMm in Arm wouldn't produce Hob by itself [3] but
other software stack should pass boot information via PHIT Hob.

To make compatible with edk2 patches [3],
add HOB creation to load StandaloneMm properly.

Also, StandaloneMm doesn't support under FF-A v1.2 version ABI.
For this, update syscall handler with FF-A v1.2 compatiblity.

Links: https://uefi.org/sites/default/files/resources/PI_Spec_1_6.pdf [1]
Links: https://edk2.groups.io/g/devel/topic/103675962#114283 [2]
Links: tianocore/edk2#6116 [3]

[jenswi-linaro]

Why is this HOB needed if StMM could create it by itself before? What is the long-term goal with StMM? Should it be turned into an SP or something else?

[LeviYeoReum]

Why is this HOB needed if StMM could create it by itself before? What is the long-term goal with StMM? Should it be turned into an SP or something else?

Since StandaloneMm (StMM) is not producer of HOB but consumer according to specification,
StMM couldn't create HOB by itslef anymore.
Formerly, the creating HOB in StMM is against specification. So edk2 patches're required.

As long term, there is plan for StMM to move SP,
but before moving to StMM SP for support exist platform (i.e) RPMB
This patch is written.

Thanks.

[jenswi-linaro]

Once StMM is an SP, who will create the HOB for StMM? How is this accommodated in the FF-A spec? Or do you anticipate a shim? If so how is that implemented?

[LeviYeoReum]

Once StMM is an SP, who will create the HOB for StMM? How is this accommodated in the FF-A spec? Or do you anticipate a shim? If so how is that implemented?

TBH, I don't know exactly, But I think SPMC should create the HOB information according to manifest file.
(i.e. TF-A with SPMC_AT_EL3: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/30481/17/services/std_svc/spm/el3_spmc/spmc_setup.c#104).

This build hob list passed via FF-A boot protocol and StMM get Hob List in FF-A boot protocol and initialize itself with it.

[jenswi-linaro]

Do you expect to merge the same thing in Hafnium?
It looks strange that a generic component like SPMC should need custom glue code for StMM, not in one place but in three places, TF-A SPMC, OP-TEE SPMC, and Hafnium SPMC. Have you considered adding a shim to the StMM binary to create the HOB from the manifest before handing control over to StMM?

[LeviYeoReum]

Do you expect to merge the same thing in Hafnium? It looks strange that a generic component like SPMC should need custom glue code for StMM, not in one place but in three places, TF-A SPMC, OP-TEE SPMC, and Hafnium SPMC. Have you considered adding a shim to the StMM binary to create the HOB from the manifest before handing control over to StMM?

No, It's not glue code for StMM, But it's based on the FF-A specfication.
Because according to FF-A Boot protocol, It can pass "HobList" instead of "FDT".
That's why in near future, there will be patch for Hafnium to sending HobList.

The FF-A boot protocol and its contents should be created from SPMC when it loads partition.
So, It's not a glue code but add a way which spec describes.

[jenswi-linaro]

Thanks, I've found it in the spec too. :-)
I'll review with that in mind.

[jenswi-linaro]

We should go with the lib approach as in TF-A. Please move all the HOB-related code under core/lib/libefi.
hob.c to core/lib/libefi/hob.c and the .h files needed outside of hob.c under core/lib/libefi/include/efi.
I'm choosing libefi over libhob since we need a prefix for the exported functions and I think the efi_ looks better than hob_.

[LeviYeoReum]

We should go with the lib approach as in TF-A. Please move all the HOB-related code under core/lib/libefi. hob.c to core/lib/libefi/hob.c and the .h files needed outside of hob.c under core/lib/libefi/include/efi. I'm choosing libefi over libhob since we need a prefix for the exported functions and I think the efi_ looks better than hob_.

Thanks for reviewing this :)
I'll move it :)