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From: "Roedel, Joerg" <Joerg.Roedel@amd.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Andreas Hartmann <andihartmann@01019freenet.de>,
	<kvm@vger.kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci <linux-pci@vger.kernel.org>
Subject: Re: vfio: missing patch in linux 3.6
Date: Fri, 5 Oct 2012 15:08:57 +0200
Message-ID: <20121005130857.GX4009@amd.com> (raw)
In-Reply-To: <1349368080.2759.52.camel@ul30vt.home>

On Thu, Oct 04, 2012 at 10:28:00AM -0600, Alex Williamson wrote:
> There are a couple questions in the link above.  Since the devices don't
> expose a PCIe capability, we probably need to add a check to look at the
> upstream device and verify we're not on a legacy bus where ACS can't be
> enforced.

You can certainly do that, but for existing hardware (with an AMD IOMMU)
this check would never be true. These devices are always on a seperate
south-bridge chip which is connected to the north-bridge via PCIe. So
the topology where you find these devices is always the same in an AMD
IOMMU system.

> Then there's the general question of whether the confirmation
> of no peer-to-peer applies to every case where we might see this device
> (some of them seem to have history that pre-dates this specific package
> implementation) or do we need to try to identify specific package
> properties in addition to just a device ID?

The device ids are kept the same to maintain compatability with older
software. Besides that, my statement about the peer-2-peer safety is
true for all south-bridges that you can find in an AMD IOMMU capable
system.

Regards,

	Joerg

-- 
AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632


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Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-04 15:13 Andreas Hartmann
2012-10-04 15:26 ` Alex Williamson
2012-10-04 15:57   ` Andreas Hartmann
2012-10-04 16:14   ` Roedel, Joerg
2012-10-04 16:28     ` Alex Williamson
2012-10-05 13:08       ` Roedel, Joerg [this message]
2012-10-14 15:07         ` Andreas Hartmann

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