VFIO mdev aggregated resources handling

Current mdev device create interface depends on fixed mdev type, which get uuid from user to create instance of mdev device. If user wants to use customized number of resource for mdev device, then only can create new mdev type for that which may not be flexible. This requirement comes not only from to be able to allocate flexible resources for KVMGT, but also from Intel scalable IO virtualization which would use vfio/mdev to be able to allocate arbitrary resources on mdev instance. More info on [1] [2] [3].

To allow to create user defined resources for mdev, it trys to extend mdev create interface by adding new "aggregate=xxx" parameter following UUID, for target mdev type if aggregation is supported, it can create new mdev device which contains resources combined by number of instances, e.g

    echo "<uuid>,aggregate=10" > create

VM manager e.g libvirt can check mdev type with "aggregation" attribute which can support this setting. If no "aggregation" attribute found for mdev type, previous behavior is still kept for one instance allocation. And new sysfs attribute "aggregated_instances" is created for each mdev device to show allocated number.

References:
[1] https://software.intel.com/en-us/download/intel-virtualization-technology-for-directed-io-architecture-specification
[2] https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification
[3] https://schd.ws/hosted_files/lc32018/00/LC3-SIOV-final.pdf

v2:
- Add new create_with_instances driver hook
- Update doc for new attributes

v3:
- Rename parameter and attribute names from review
- Make "aggregation" attribute to show maxium resource number for aggregation
- Check driver hooks for attribute create validation
- Update doc and ABI spec

Zhenyu Wang (6):
vfio/mdev: Add new "aggregate" parameter for mdev create vfio/mdev: Add "aggregation" attribute for supported mdev type vfio/mdev: Add "aggregated_instances" attribute for supported mdev
device
Documentation/vfio-mediated-device.txt: Update for vfio/mdev
aggregation support
Documentation/ABI/testing/sysfs-bus-vfio-mdev: Update for vfio/mdev
aggregation support
drm/i915/gvt: Add new type with aggregation support

 Documentation/ABI/testing/sysfs-bus-vfio-mdev | 25 +++++++
 Documentation/vfio-mediated-device.txt        | 44 +++++++++--
 drivers/gpu/drm/i915/gvt/gvt.h                | 11 ++-
 drivers/gpu/drm/i915/gvt/kvmgt.c              | 53 ++++++++++++-
 drivers/gpu/drm/i915/gvt/vgpu.c               | 56 +++++++++++++-
 drivers/vfio/mdev/mdev_core.c                 | 40 +++++++++-
 drivers/vfio/mdev/mdev_private.h              |  6 +-
 drivers/vfio/mdev/mdev_sysfs.c                | 74 ++++++++++++++++++-
 include/linux/mdev.h                          | 19 +++++
 9 files changed, 305 insertions(+), 23 deletions(-)

2.19.1