On Sat, 9 Aug 2025 17:55:19 +0200
Mauro Carvalho Chehab [off-list ref] wrote:

Em Fri, 8 Aug 2025 16:22:09 +0100
Jonathan Cameron [off-list ref] escreveu:

quoted

On Tue, 05 Aug 2025 11:35:38 -0700
Daniel Ferguson [off-list ref] wrote:
  

quoted

From: Jason Tian <redacted>

The ARM processor CPER record was added in UEFI v2.6 and remained
unchanged up to v2.10.

Yet, the original arm_event trace code added by

  e9279e83ad1f ("trace, ras: add ARM processor error trace event")

is incomplete, as it only traces some fields of UAPI 2.6 table N.16, not
exporting any information from tables N.17 to N.29 of the record.

This is not enough for the user to be able to figure out what has
exactly happened or to take appropriate action.

According to the UEFI v2.9 specification chapter N2.4.4, the ARM
processor error section includes:

- several (ERR_INFO_NUM) ARM processor error information structures
  (Tables N.17 to N.20);
- several (CONTEXT_INFO_NUM) ARM processor context information
  structures (Tables N.21 to N.29);
- several vendor specific error information structures. The
  size is given by Section Length minus the size of the other
  fields.

In addition, it also exports two fields that are parsed by the GHES
driver when firmware reports it, e.g.:

- error severity
- CPU logical index

Report all of these information to userspace via a the ARM tracepoint so
that userspace can properly record the error and take decisions related
to CPU core isolation according to error severity and other info.

The updated ARM trace event now contains the following fields:

======================================  =============================
UEFI field on table N.16                ARM Processor trace fields
======================================  =============================
Validation                              handled when filling data for
                                        affinity MPIDR and running
                                        state.
ERR_INFO_NUM                            pei_len
CONTEXT_INFO_NUM                        ctx_len
Section Length                          indirectly reported by
                                        pei_len, ctx_len and oem_len
Error affinity level                    affinity
MPIDR_EL1                               mpidr
MIDR_EL1                                midr
Running State                           running_state
PSCI State                              psci_state
Processor Error Information Structure   pei_err - count at pei_len
Processor Context                       ctx_err- count at ctx_len
Vendor Specific Error Info              oem - count at oem_len
======================================  =============================

It should be noted that decoding of tables N.17 to N.29, if needed, will
be handled in userspace. That gives more flexibility, as there won't be
any need to flood the kernel with micro-architecture specific error
decoding.

Also, decoding the other fields require a complex logic, and should be
done for each of the several values inside the record field.  So, let
userspace daemons like rasdaemon decode them, parsing such tables and
having vendor-specific micro-architecture-specific decoders.

  [mchehab: modified description, solved merge conflicts and fixed coding style]

Fixes: e9279e83ad1f ("trace, ras: add ARM processor error trace event")
    

Fixes tag is part of the main tag block so no blank line here.
There are at least some scripts running on the kernel tree that trip
up on this (and one that moans at the submitter ;)

I'd also add something to explain the SoB sequence for the curious.
  

quoted

Co-developed-by: Jason Tian <redacted>    

Jason's the Author, so shouldn't have a Co-dev tag.
There is some info on this in
https://docs.kernel.org/process/submitting-patches.html  

My understanding is that all co-authors shall have co-developed-by
and SoB. Anyway, doesn't matter much in practice, I guess.

Nope.  In the description the docs say "in addition to the author
attribute in the From: tag"  There are also examples where there
isn't a Co-dev for the From author including the subtle question of
ordering if someone else posts that patch.

I have a vague recollection one of the scripts checking linux-next
might moan about this. 

quoted

quoted

Signed-off-by: Jason Tian <redacted>
Co-developed-by: Shengwei Luo <redacted>
Signed-off-by: Shengwei Luo <redacted>
Co-developed-by: Daniel Ferguson <redacted>
Signed-off-by: Daniel Ferguson <redacted>    

As person submitting I'd normally expect your SoB last.
  

quoted

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>    

I guess this is because Mauro posted an earlier version in which
case this is arguably correct, but likely to confuse.
For cases like this I add comments.  

If the patch is identical, and it is just a resubmission,
I would keep the original order.

Otherwise, if Daniel did some changes at the code (except for a
trivial rebase stuff), better to move his co-developed-by/SoB to
the end, eventually adding:

[Daniel: <did something>] before the custody chain block.

Docs are clear that sender of the patch must be last SoB.
That's also checked by the some of the tag block check scripts
I think.  There's an example of exactly this case in the in the
submitting-patches.rst file (last one in the section that talks
about Co-developed-by.

For meaning I don't care that much, but keeping to the rigid
rules in that doc makes it easier for scripts to check for the
more important stuff like whether all necessary SoB are there.

Jonathan

Thanks,
Mauro