[PATCH RFC 0/4] iommu: Add support to change default domain of a group

[Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>]

Presently, the default domain of a group is allocated during boot time and it
cannot be changed later. So, the device would typically be either in
identity/pass through mode or the device would be in DMA mode as long as the
system is up and running. There is no way to change the default domain type
dynamically i.e. after booting, a device cannot switch between identity mode and
DMA mode.

Assume a use case where-in the priviliged user would want to use the device in
pass-through mode when the device is used for host but would want to switch to
dma protected mode when switching for VFIO in user space. Presently, this is not
supported and hence add support to change default domain of a group dynamically.

Support this through a sysfs file, namely "/sys/kernel/iommu_groups/<grp_id>/type".

Testing:
--------
Tested by dynamically changing USB device from identity mode to dma and from dma
to identity. Only for x86_64 (i.e. intel_iommu/vt-d). Haven't tested for other
architectures.

Sai Praneeth Prakhya (4):
  iommu/vt-d: Modify device_def_domain_type() to use at runtime
  iommu: Add device_def_domain_type() call back function to iommu_ops
  iommu: Add support to change default domain of a group
  iommu: Document usage of "/sys/kernel/iommu_groups/<grp_id>/type" file

 .../ABI/testing/sysfs-kernel-iommu_groups     |  34 ++++
 drivers/iommu/intel-iommu.c                   |  32 +++-
 drivers/iommu/iommu.c                         | 178 +++++++++++++++++-
 include/linux/iommu.h                         |   3 +
 4 files changed, 237 insertions(+), 10 deletions(-)

Cc: Christoph Hellwig <hch@lst.de>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Sohil Mehta <sohil.mehta@intel.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>

-- 
2.19.1

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