[PATCH v2 0/3] Correct for ACPI 5.1->6.0 spec changes in MADT GICC entries

Al Stone ahs3 at redhat.com
Tue Jun 30 10:29:35 PDT 2015

On 06/30/2015 11:07 AM, Sudeep Holla wrote:
> Hi Al,
> On 18/06/15 23:36, Al Stone wrote:
>> In the ACPI 5.1 version of the spec, the struct for the GICC subtable
>> (struct acpi_madt_generic_interrupt) of the MADT is 76 bytes long; in
>> ACPI 6.0, the struct is 80 bytes long.  But, there is only one definition
>> in ACPICA for this struct -- and that is the 6.0 version.  Hence, when
>> BAD_MADT_ENTRY() compares the struct size to the length in the GICC
>> subtable, it fails if 5.1 structs are in use, and there are systems in
>> the wild that have them.
>> Note that this was found in linux-next and these patches apply against
>> that tree and the arm64 kernel tree; 4.1-rc8 does not appear to have this
>> problem since it still has the 5.1 struct definition.
>> Even though there is precendent in ia64 code for ignoring the changes in
>> size, this patch set instead tries to verify correctness.  The first patch
>> in the set adds macros for easily using the ACPI spec version.  The second
>> patch adds the BAD_MADT_GICC_ENTRY() macro that uses the version macros to
>> check the GICC subtable only, accounting for the difference in specification
>> versions that are possible.  The final patch replaces BAD_MADT_ENTRY usage
>> with the BAD_MADT_GICC_ENTRY macro in arm64 code, which is currently the
>> only architecture affected.  The BAD_MADT_ENTRY() will continue to work as
>> is for all other MADT subtables.
> We need to get this series or a patch to remove the check(similar to
> ia64) based on what Rafael prefers. Without that, platforms using ACPI
> on ARM64 fails to boot with latest mainline. This blocks any testing on
> ARM64/ACPI systems.
> Regards,
> Sudeep

I have not received any other feedback than some Reviewed-bys from
Hanjun and an ACK from Will for the arm64 patch.

And absolutely agreed: this is a blocker for arm64/ACPI, starting with
the ACPICA 20150515 patches which appear to have gone in with 4.2-rc1.

Rafael?  Ping?  Do we need these to go through your tree or the arm64
tree?  Without this series (or an ia64-like solution), we have ACPI
systems in the field that cannot boot.

Al Stone
Software Engineer
Red Hat, Inc.
ahs3 at redhat.com

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