linux-kernel - Re: [tip:x86/apic] x86: Fix out of order gsi -- add remap_ioapic_gsi_to

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Message-ID: <m1y6ieo5zw.fsf@fess.ebiederm.org>
Date:	Sat, 27 Feb 2010 11:04:03 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Ingo Molnar <mingo@...e.hu>
Cc:	tip-bot for Yinghai Lu <yinghai@...nel.org>,
	linux-tip-commits@...r.kernel.org, linux-kernel@...r.kernel.org,
	hpa@...or.com, mingo@...hat.com, garyhade@...ibm.com,
	iranna.ankad@...ibm.com, suresh.b.siddha@...el.com,
	tglx@...utronix.de, trenn@...e.de
Subject: Re: [tip:x86/apic] x86: Fix out of order gsi -- add remap_ioapic_gsi_to_irq()

Ingo Molnar <mingo@...e.hu> writes:

> Causes:
>
>  arch/x86/kernel/apic/io_apic.c:1042: error: implicit declaration of function ?remap_ioapic_gsi_to_irq?
>
> Please send delta fix.

I am certain I have said this before but the entire concept of 
irq != gsi is broken.  We used to have code that did this and it was a
non-ending source of problems that we finally removed after we pushed
up the limit on the number of irqs.

We already have the irq_2_pin list which allows for arbitrary mappings
between irqs and the ioapics and pins.  So there should be no problem
mapping irq to gsi and assigning irqs to arbitrary ioapic pins.

I have yet to see something that even purports to be an explanation
of why our handling of acpi int_src_overrides is broken and why
it needs the mess that is a remapper.

I don't doubt YHs changes fix something but this feels like a direction
that trades off one bug for another instead of actually fixing the code.

It does look like we have weird old hard codes in some of the
irq_2_pin and pin_2_irq paths that YH is touching, and it may make sense
to introduce a concept of ioapic pin index.  

The touching of drivers/pnp/pnpacpi/rsparser.c feels like just the tip of
the iceberg in dealing with weird bugs if we continue down this path.

Eric
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