hulk inclusion
category: feature
bugzilla: 14369
CVE: NA
-------------------

Allocate IOMMU mm structures and binding them to devices. Four operations
are added to IOMMU drivers:

* mm_alloc(): to create an io_mm structure and perform architecture-
  specific operations required to grab the process (for instance on ARM,
  pin down the CPU ASID so that the process doesn't get assigned a new
  ASID on rollover).

  There is a single valid io_mm structure per Linux mm. Future extensions
  may also use io_mm for kernel-managed address spaces, populated with
  map()/unmap() calls instead of bound to process address spaces. This
  patch focuses on "shared" io_mm.

* mm_attach(): attach an mm to a device. The IOMMU driver checks that the
  device is capable of sharing an address space, and writes the PASID
  table entry to install the pgd.

  Some IOMMU drivers will have a single PASID table per domain, for
  convenience. Other can implement it differently but to help these
  drivers, mm_attach and mm_detach take 'attach_domain' and
  'detach_domain' parameters, that tell whether they need to set and clear
  the PASID entry or only send the required TLB invalidations.

* mm_detach(): detach an mm from a device. The IOMMU driver removes the
  PASID table entry and invalidates the IOTLBs.

* mm_free(): free a structure allocated by mm_alloc(), and let arch
  release the process.

mm_attach and mm_detach operations are serialized with a spinlock. When
trying to optimize this code, we should at least prevent concurrent
attach()/detach() on the same domain (so multi-level PASID table code can
allocate tables lazily). mm_alloc() can sleep, but mm_free must not
(because we'll have to call it from call_srcu later on).

At the moment we use an IDR for allocating PASIDs and retrieving contexts.
We also use a single spinlock. These can be refined and optimized later (a
custom allocator will be needed for top-down PASID allocation).

Keeping track of address spaces requires the use of MMU notifiers.
Handling process exit with regard to unbind() is tricky, so it is left for
another patch and we explicitly fail mm_alloc() for the moment.
Signed-off-by: NJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: NFang Lijun <fanglijun3@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Reviewed-by: NZhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>