linux-kernel - Re: [git pull] IOMMU Updates for v3.7-rc1

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Message-ID: <20121011093239.GA2619@amd.com>
Date:	Thu, 11 Oct 2012 11:32:39 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Andrew Oakley <andrew@....is-a-geek.net>
CC:	<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] IOMMU Updates for v3.7-rc1

On Wed, Oct 10, 2012 at 11:02:31PM +0100, Andrew Oakley wrote:
> On Wed, 10 Oct 2012 20:11:31 +0100
> Andrew Oakley <andrew@....is-a-geek.net> wrote:

> I'm not sure if the fix I've got is safe or if it's really a good idea
> to enable interrupt remapping with a broken BIOS.

Sadly it is not. Your patch works for your particular case but is not
generally applicable. There are indeed systems with 2 or more IOAPICs
and they all use different device-ids.

So, typically, there is one IOAPIC per SB, like in your case. But on
RD890 the chipset NB also includes an IOAPIC (which uses
device-id 00:00.1). This IOAPIC exists on your system too but is
disabled by the BIOS because the board does not use it.

So, in the end, device-id 00:00.1 might also be correct and the IVRS
entry could refer to the NB IOAPIC. We don't have any reliable
indication which IOAPIC is described in the IVRS table.

Cheer,

	Joerg

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