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:	Wed, 1 Jul 2015 10:06:53 +0800
From:	Hanjun Guo <guohanjun@...wei.com>
To:	"Rafael J. Wysocki" <rafael@...nel.org>, Al Stone <ahs3@...hat.com>
CC:	Sudeep Holla <sudeep.holla@....com>,
	Al Stone <al.stone@...aro.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"lenb@...nel.org" <lenb@...nel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"patches@...aro.org" <patches@...aro.org>
Subject: Re: [PATCH v2 0/3] Correct for ACPI 5.1->6.0 spec changes in MADT
 GICC entries

On 2015/7/1 2:35, Rafael J. Wysocki wrote:
> On Tue, Jun 30, 2015 at 8:25 PM, Rafael J. Wysocki <rafael@...nel.org> wrote:
>> Hi Al,
>>
>> On Tue, Jun 30, 2015 at 7:29 PM, Al Stone <ahs3@...hat.com> wrote:
>>> On 06/30/2015 11:07 AM, Sudeep Holla wrote:
>>>> Hi Al,
>>>>
>>>> On 18/06/15 23:36, 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.
>>>>>
>>>> We need to get this series or a patch to remove the check(similar to
>>>> ia64) based on what Rafael prefers. Without that, platforms using ACPI
>>>> on ARM64 fails to boot with latest mainline. This blocks any testing on
>>>> ARM64/ACPI systems.
>>>>
>>>> Regards,
>>>> Sudeep
>>> I have not received any other feedback than some Reviewed-bys from
>>> Hanjun and an ACK from Will for the arm64 patch.
>>>
>>> And absolutely agreed: this is a blocker for arm64/ACPI, starting with
>>> the ACPICA 20150515 patches which appear to have gone in with 4.2-rc1.
>>>
>>> Rafael?  Ping?
>> I overlooked the fact that this was needed to fix a recent regression,
>> sorry about that.
>>
>> Actually, if your patch fixes an error introduced by a specific
>> commit, it is good to use the Fixes: tag to indicate that.  Which I
>> still would like to do, so which commit is fixed by this?
>>
>>> Do we need these to go through your tree or the arm64
>>> tree?  Without this series (or an ia64-like solution), we have ACPI
>>> systems in the field that cannot boot.
>> I'm not quite sure why the definition of BAD_MADT_GICC_ENTRY has to go
>> into include/linux/acpi.h.  Why is it necessary in there?
> Like what about defining it in linux/irqchip/arm-gic-acpi.h for example?
>

This BAD_MADT_GICC_ENTRY is both used by SMP init and GIC irqchip init for
ARM64, would it be good to put BAD_MADT_GICC_ENTRY in arch/arm64/include/asm/acpi.h?

Thanks
Hanjun

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