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

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Date:	Tue, 7 Jul 2015 01:20:51 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Al Stone <al.stone@...aro.org>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"patches@...aro.org" <patches@...aro.org>
Subject: Re: [PATCH v4 0/2] Correct for ACPI 5.1->6.0 spec changes in MADT
 GICC entries

Hi Al,

On Tue, Jul 7, 2015 at 1:16 AM, Al Stone <al.stone@...aro.org> 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 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?

Rafael
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