linux-kernel - Re: [Patch v2] x86, ACPI, irq: Add a quirk to override SCI polarity for HyperV

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Message-ID: <alpine.DEB.2.11.1508191025000.3873@nanos>
Date:	Wed, 19 Aug 2015 10:29:02 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Nick Meier <nmeier@...rosoft.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [Patch v2] x86, ACPI, irq: Add a quirk to override SCI polarity
 for HyperV

On Wed, 19 Aug 2015, Jiang Liu wrote:
> On 2015/8/19 14:45, Rafael J. Wysocki wrote:
> > Well, the regression at hand has just shown that the assertion in the
> > changelog of that commit ("no need for for special treatment for GSI
> > used by ACPI SCI") does not really hold.  So, if the only motivation
> > for it was to get rid of one extra check in mp_unregister_gsi()
> > (mp_register_gsi() still needs to check if it is dealing with the SCI
> > anyway), I'd vote for reverting it.
> Hi Rafael,
> 	The motivation is to treat SCI as normal IOAPIC interrupt so
> we could enforce stricter pin attribute checking. Now it does reveal
> flaws in ACPI BIOS implementations, but we ran into trouble about how to
> handle those flaws:(

The intent of this change is entirely correct, though it seems that
reality of ACPI is just different.

To be on the safe side of things, I agree with Rafael that we should
revert that patch instead of introducing a single platform quirk.

What we can do is to emit a pr_warn() if we detect inconsistency of
the SCI configuration. That way we might be able to gather information
how wide spread this disease is.

Thanks,

	tglx



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