RFC iommu: APIs for paravirtual PASID allocation

This adds an uniformed API set for global PASIDs used by IOMMU and device drivers which depend on IOMMU. It works for drivers running on bare metal, full virtualized environments and para- virtualized environment.

When PASID requests come from components running on the bare metal hardware, the requests will be routed to the system wide I/O ASID allocator.

            ^   ^  iommu_pasid_init() 
            |   |  iommu_pasid_exit() 
            |   |  iommu_pasid_alloc()
            |   |  iommu_pasid_free() 

.-------------------------------.
| IOMMU PASID APIs |
'-------------------------------'
| ^
v |
.------------. .---------------.
| I/O ASID | | |
| allocator | | IOMMU drivers |
| (drivers/ | | or |
| base/ | | virtio IOMMU |
| ioasid.c) | | |
'------------' '---------------'

When PASID requests come from components running in full-virtualized or para-virtualized environments, they will be routed to the vendor- specific or virtio IOMMU driver, where the requests will be intercepted and routed to the Host Linux via VFIO interfaces.

    ......................................
    .            Guest Linux             .
    ......................................
    .                                    .
    . .----------------------------.     .
    . |       IOMMU PASID APIs     |     .
    . '----------------------------'     .
    .                           |        .
    .                           v        .
    .  .----------. .---------------.    ..---------.
    .  | I/O ASID | | IOMMU drivers |    .|  QEMU   |
    .  '----------' | /virtio IOMMU |---->'---------'
    .               '---------------'    .| virtio  |
    ......................................'---------'
                                               |
                                               |
    ...........................................|....
    .                  Host Linux              |   .
    ...........................................|....
    .                      |-------------------'   .
    .                      v                       .
    .         .----------------------------.       .
    .         |       IOMMU PASID APIs     |       .
    .         '----------------------------'       .
    .               |                              .
    .               v       .---------------.      .
    .         .----------.  | IOMMU drivers |      .
    .         | I/O ASID |  | /virtio IOMMU |      .
    .         '----------'  '---------------'      .
    ................................................

Below APIs are introduced:

* iommu_pasid_init(pasid)
- Initialize a PASID consumer. The vendor specific IOMMU drivers are able to set the PASID range imposed by IOMMU hardware through a callback in iommu_ops.

* iommu_pasid_exit(pasid)
- The PASID consumer stops consuming any PASID.

* iommu_pasid_alloc(pasid, min, max, private, *ioasid)
- Allocate a PASID and associate a @private data with this PASID. The PASID value is stored in @ioaisd if returning success.

* iommu_pasid_free(pasid, ioasid)
- Free a PASID to the pool so that it could be consumed by others.

It also adds below helpers to lookup or iterate PASID items.

* iommu_pasid_for_each(pasid, func, data)
- Iterate PASID items of the consumer identified by @pasid, and call @func() against each item. An error returned from @func() will break the iteration.

* iommu_pasid_find(pasid, ioasid)
- Retrieve the private data associated with @ioasid.

This patch set depends on the I/O APSID allocator posted here
[1] for discussion.

[1] https://www.spinics.net/lists/iommu/msg30639.html

Best regards,
Lu Baolu

Lu Baolu (5):
iommu: Add APIs for IOMMU PASID management
iommu/vt-d: Initialize a PASID consumer
iommu/vt-d: Enlightened PASID allocation
iommu/vt-d: Allocate and free a pasid
iommu/vt-d: Use global pasid allocator

 drivers/iommu/Kconfig       |  1 +
 drivers/iommu/intel-iommu.c | 83 +++++++++++++++++++++++++++++++---
 drivers/iommu/intel-pasid.c | 88 +++++++++++++++++++++++++-----------
 drivers/iommu/intel-pasid.h | 16 +++++--
 drivers/iommu/intel-svm.c   | 24 +++++-----
 drivers/iommu/iommu.c       | 89 +++++++++++++++++++++++++++++++++++++
 include/linux/intel-iommu.h |  5 +++
 include/linux/iommu.h       | 73 ++++++++++++++++++++++++++++++
 8 files changed, 332 insertions(+), 47 deletions(-)

2.17.1