[PATCH v4 0/2] Correct for ACPI 5.1->6.0 spec changes in MADT GICC entries

Al Stone ahs3 at redhat.com
Mon Jul 6 16:45:40 PDT 2015

On 07/06/2015 05:20 PM, Rafael J. Wysocki wrote:
> Hi Al,
> On Tue, Jul 7, 2015 at 1:16 AM, Al Stone <al.stone at linaro.org> 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 does not appear to have this
>> problem since it still has the 5.1 struct definition.
>> Though there is precedent in ia64 code for ignoring the changes in size,
>> this patch set instead verifies correctness.  The first patch adds the
>> BAD_MADT_GICC_ENTRY() macro to check the GICC subtable only, accounting
>> for the difference in specification versions that are possible.  The
>> second 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.
>> I have tested these patches on an APM Mustang with version 1.15 firmware,
>> where the problem was found, and they fix the problem -- i.e., the system
>> will boot with either Linux 4.1 or linux-next kernels using the same ACPI
>> 5.1 compatible firmware.
> ACK for the series, but I guess it's better to let it go via ARM64, right?
> Rafael

Thanks, Rafael.  Yeah, probably so.  Will has ACKd the one patch
(2/2); if he and/or Catalin ACK patch 1/2, then this seems like it
would pretty cleanly fit into ARM64.  The only question would be if
Will or Catalin would want an ACK from Thomas on the irq-gic.c part
in 2/2.

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

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