linux-kernel - Re: PCI: MSI interrupts masked using prohibited method

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Message-Id: <200806251420.51751.jbarnes@virtuousgeek.org>
Date:	Wed, 25 Jun 2008 14:20:51 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	David Vrabel <david.vrabel@....com>
Cc:	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: PCI: MSI interrupts masked using prohibited method

On Tuesday, June 24, 2008 3:46 am David Vrabel wrote:
> PCI MSI interrupts are masked and unmasked using a method (by writing
> the MSI Enable capability bit) that is prohibited by the PCI specification.

Yeah, it's probably quite a bit slower too (I assume you're talking about 
io_apic_64's msi_mask_irq).  Seems like masking this at the ioapic level 
would make more sense anyway...

> This behaviour can cause missed interrupts with some devices if the
> interrupt is asserted by the hardware while MSI is disabled.
>
> I believe the interrupt should be masked/unmasked on the interrupt
> controller (the APIC on x86, for example).   I'm going to test this now
> and see if it works.

Great, thanks.

Jesse
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