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

Al Stone ahs3 at redhat.com
Tue Jul 7 08:07:56 PDT 2015

On 07/07/2015 07:31 AM, Catalin Marinas wrote:
> On Tue, Jul 07, 2015 at 01:20:51AM +0200, Rafael J. Wysocki wrote:
>> 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?
> Fine by me. I'll pick them up for 4.2-rc2.
> Thanks.

Thanks, Catalin.  Holler if there's any problems.

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

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