Re: [PATCH 02/13] iommu: IOMMU Groups

From: Alex Williamson
Date: Fri May 11 2012 - 19:58:49 EST

On Fri, 2012-05-11 at 16:39 -0700, Greg KH wrote:
> On Fri, May 11, 2012 at 04:55:41PM -0600, Alex Williamson wrote:
> > IOMMU device groups are currently a rather vague associative notion
> > with assembly required by the user or user level driver provider to
> > do anything useful. This patch intends to grow the IOMMU group concept
> > into something a bit more consumable.
> >
> > To do this, we first create an object representing the group, struct
> > iommu_group. This structure is allocated (iommu_group_alloc) and
> > filled (iommu_group_add_device) by the iommu driver. The iommu driver
> > is free to add devices to the group using it's own set of policies.
> > This allows inclusion of devices based on physical hardware or topology
> > limitations of the platform, as well as soft requirements, such as
> > multi-function trust levels or peer-to-peer protection of the
> > interconnects. Each device may only belong to a single iommu group,
> > which is linked from struct device.iommu_group. IOMMU groups are
> > maintained using kobject reference counting, allowing for automatic
> > removal of empty, unreferenced groups. It is the responsibility of
> > the iommu driver to remove devices from the group
> > (iommu_group_remove_device).
> >
> > IOMMU groups also include a userspace representation in sysfs under
> > /sys/kernel/iommu_groups. When allocated, each group is given a
> > dynamically assign ID (int). The ID is managed by the core IOMMU group
> > code to support multiple heterogeneous iommu drivers, which could
> > potentially collide in group naming/numbering. This also keeps group
> > IDs to small, easily managed values. A directory is created under
> > /sys/kernel/iommu_groups for each group. A further subdirectory named
> > "devices" contains links to each device within the group. The iommu_group
> > file in the device's sysfs directory, which formerly contained a group
> > number when read, is now a link to the iommu group. Example:
> >
> > $ ls -l /sys/kernel/iommu_groups/26/devices/
> <snip>
> As you are creating new sysfs files and directories, you need to also
> add the proper Documentation/ABI/ files at the same time.

I'll update. Thanks,


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at