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Date: Mon, 22 Aug 2011 09:30:26 +0300
From: Avi Kivity <avi@redhat.com>
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To: Alex Williamson <alex.williamson@redhat.com>
Subject: Re: kvm PCI assignment & VFIO ramblings
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Cc: chrisw <chrisw@sous-sol.org>, Alexey Kardashevskiy <aik@au1.ibm.com>,
	kvm@vger.kernel.org, Paul Mackerras <pmac@au1.ibm.com>,
	qemu-devel <qemu-devel@nongnu.org>, aafabbri <aafabbri@cisco.com>,
	iommu <iommu@lists.linux-foundation.org>,
	Anthony Liguori <anthony@codemonkey.ws>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
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On 08/20/2011 07:51 PM, Alex Williamson wrote:
> We need to address both the description and enforcement of device
> groups.  Groups are formed any time the iommu does not have resolution
> between a set of devices.  On x86, this typically happens when a
> PCI-to-PCI bridge exists between the set of devices and the iommu.  For
> Power, partitionable endpoints define a group.  Grouping information
> needs to be exposed for both userspace and kernel internal usage.  This
> will be a sysfs attribute setup by the iommu drivers.  Perhaps:
>
> # cat /sys/devices/pci0000:00/0000:00:19.0/iommu_group
> 42
>

$ readlink /sys/devices/pci0000:00/0000:00:19.0/iommu_group
../../../path/to/device/which/represents/the/resource/constraint

(the pci-to-pci bridge on x86, or whatever node represents partitionable 
endpoints on power)

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.