linux-kernel - Re: What are the real ioapic rte programming constraints?

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Message-id: <Pine.LNX.4.64.0702111416220.24829@montezuma.fsmlabs.com>
Date:	Sun, 11 Feb 2007 17:05:12 -0800 (PST)
From:	Zwane Mwaikambo <zwane@...radead.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Ashok Raj <ashok.raj@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	"Lu, Yinghai" <yinghai.lu@....com>,
	Natalie Protasevich <protasnb@...il.com>,
	Andi Kleen <ak@...e.de>
Subject: Re: What are the real ioapic rte programming constraints?

On Sun, 11 Feb 2007, Eric W. Biederman wrote:

> > 2.15.2 PCI Express* Legacy INTx Support and Boot Interrupt
> > http://download.intel.com/design/chipsets/datashts/30262802.pdf
> 
> Ouch.  And this kind of thing isn't exactly uncommon.
> 
> However if we have the irqs also disabled in the i8259 we should
> be safe from actually receiving this interrupt (even if it generates
> bus traffic), and when we enable the irq since it is level triggered  
> we should still get an interrupt message.
>
> It isn't immediately obvious where the i8259 irq enable/disable
> happens.  So i"m having trouble auditing that bit of code.
>
> Plus we can get very strange things like the irq number changing
> and the sharing rules being different when going through the i8259.
> So irqN may be irqM when going through the i8259.
> 
> As long as we aren't using anything on the i8259 including the timer
> in ExtINT mode we can disable every interrupt pin and not worry about
> interrupts from that source.

We do the 8259 mask in setup_IO_APIC_irq. does anyone have access to an 
E7520/E7320 system for testing?

Cheers,
	Zwane

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