linux-kernel - Re: [PATCH v3 2/3] ACPI / ARM64: add BAD_MADT_GICC

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Message-ID: <20150706103355.GC27723@e104818-lin.cambridge.arm.com>
Date:	Mon, 6 Jul 2015 11:33:55 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Al Stone <ahs3@...hat.com>, linaro-kernel@...ts.linaro.org,
	jason@...edaemon.net, Al Stone <al.stone@...aro.org>,
	linaro-acpi@...ts.linaro.org, patches@...aro.org,
	will.deacon@....com, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, tglx@...utronix.de,
	linux-arm-kernel@...ts.infradead.org, lenb@...nel.org
Subject: Re: [PATCH v3 2/3] ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro

On Sat, Jul 04, 2015 at 01:54:15AM +0200, Rafael J. Wysocki wrote:
> On Friday, July 03, 2015 01:51:36 PM Al Stone wrote:
> > Perhaps the sanity checking for the MADT subtables needs to be revisited
> > and a more general solution provided -- this is not the only MADT subtable
> > with this problem and it may occur again.
> > 
> > Even the versions above are not technically compliant with the spec.  If
> > we implement what the spec currently says, it might look something like
> > this:
> > 
> > #define ACPI_MADT_GICC_LENGTH ({					\
> > 	u8 length;							\
> > 	switch (ACPI_FADT_SPEC_VERSION) {				\
> > 	case ACPI_FADT_SPEC_VERSION_5_0:				\
> > 		length = 40;						\
> > 		break;							\
> > 	case ACPI_FADT_SPEC_VERSION_5_1:				\
> > 		length = 76;						\
> > 		break;							\
> > 	default:	/* use 6.0 size */				\
> > 		length = 80;						\
> > 	}								\
> > 	length;								\
> > })
> > 
> > So it's just messy and there will be a need for change.  Let me think about
> > making this a function instead of a macro; it may make sense to really fix
> > BAD_MADT_ENTRY in general instead of just dealing with the GICC subtable,
> > but it could also be overkill.
> 
> So here's my suggestion.
> 
> First, make ARM64 boot with 4.2+ in the simplest way possible.
> 
> Second, set out to fix BAD_MADT_ENTRY() etc.  Start with fixing ACPICA to
> distinguish between the different formats depending on the spec version and
> follow up from there.

That's fine by me (as long as there is a plan to fix it properly,
ideally in 4.3).

-- 
Catalin
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