linux-kernel - Re: [PATCH v2 0/3] Correct for ACPI 5.1->6.0 spec changes in MADT GICC entries

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Date:	Fri, 19 Jun 2015 14:05:31 -0600
From:	Al Stone <ahs3@...hat.com>
To:	Hanjun Guo <hanjun.guo@...aro.org>, Al Stone <al.stone@...aro.org>,
	linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
CC:	rjw@...ysocki.net, lenb@...nel.org, catalin.marinas@....com,
	will.deacon@....com, tglx@...utronix.de, jason@...edaemon.net,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	linaro-kernel@...ts.linaro.org, patches@...aro.org
Subject: Re: [PATCH v2 0/3] Correct for ACPI 5.1->6.0 spec changes in MADT
 GICC entries

On 06/19/2015 04:54 AM, Hanjun Guo wrote:
> On 06/19/2015 06:36 AM, Al Stone 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-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.
> 
> I also tested on QEMU, it fixed the problem when I was using ACPICA 6.0
> updates for MADT table,
> 
> Tested-by: Hanjun Guo <hanjun.guo@...aro.org>
> 
> Thanks
> Hanjun

Cool.  The patches did what they should.  Looks like they work on AMD
Seattle with older firmware, also.  Thanks.

>>
>> 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: add BAD_MADT_GICC_ENTRY() macro
>>    ACPI / ARM64 : use the new BAD_MADT_GICC_ENTRY macro
>>
>>   arch/arm64/kernel/smp.c   |  2 +-
>>   drivers/irqchip/irq-gic.c |  2 +-
>>   include/linux/acpi.h      | 15 +++++++++++++++
>>   3 files changed, 17 insertions(+), 2 deletions(-)
>>
> -- 
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-- 
ciao,
al
-----------------------------------
Al Stone
Software Engineer
Red Hat, Inc.
ahs3@...hat.com
-----------------------------------
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