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.
I have tested these patches on an APM Mustang with version 1.15 firmware, where the problem was found, and they fix the problem.
Changes for v3: -- Modified the macros for using spec version numbers in order to make them clearer (Rafael, Hanjun) -- Moved the definition of the BAD_MADT_GICC_ENTRY macro to an arm64-specific header file since only this architecture uses the GICC subtable (Rafael) -- Added Reviewed-by (Hanjun) and Acked-by (Will) tags to 3/3, the only unchanged patch; other tags could be applied but the patches have changed. -- Added Fixes: tag to patches
Changes for v2: -- Replace magic constants with proper defines (Lorenzo) -- Minor syntax clean-up noted by checkpatch -- Send out CCs properly this time -- Minor clean-up of the paragraphs in this cover letter
Al Stone (3): ACPI : introduce macros for using the ACPI specification version ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro ACPI / ARM64 : use the new BAD_MADT_GICC_ENTRY macro
arch/arm64/include/asm/acpi.h | 11 +++++++++++ arch/arm64/kernel/smp.c | 2 +- drivers/irqchip/irq-gic.c | 2 +- include/linux/acpi.h | 10 ++++++++++ 4 files changed, 23 insertions(+), 2 deletions(-)