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

[Al Stone]

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.

Changes for v4:
  -- Reword the cover letter to reflect smaller patch set
  -- Simplify BAD_MADT_GICC_ENTRY to the minimum needed; this removed
     the need for the first patch containing version number macros (Rafael)
  -- Simplify determining the GICC subtable length (Catalin)

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 (2):
  ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro
  ACPI / ARM64 : use the new BAD_MADT_GICC_ENTRY macro

 arch/arm64/include/asm/acpi.h | 8 ++++++++
 arch/arm64/kernel/smp.c       | 2 +-
 drivers/irqchip/irq-gic.c     | 2 +-
 3 files changed, 10 insertions(+), 2 deletions(-)

-- 
2.4.3

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