On 07/07/2015 07:31 AM, Catalin Marinas wrote:

On Tue, Jul 07, 2015 at 01:20:51AM +0200, Rafael J. Wysocki wrote:

quoted

On Tue, Jul 7, 2015 at 1:16 AM, Al Stone [off-list ref] wrote:

quoted

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.

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