iommupt: Add map_pages op

map is slightly complicated because it has to handle a number of special
edge cases:
 - Overmapping a previously shared, but now empty, table level with an OA.
   Requries validating and freeing the possibly empty tables
 - Doing the above across an entire to-be-created contiguous entry
 - Installing a new shared table level concurrently with another thread
 - Expanding the table by adding more top levels

Table expansion is a unique feature of AMDv1, this version is quite
similar except we handle racing concurrent lockless map. The table top
pointer and starting level are encoded in a single uintptr_t which ensures
we can READ_ONCE() without tearing. Any op will do the READ_ONCE() and use
that fixed point as its starting point. Concurrent expansion is handled
with a table global spinlock.

When inserting a new table entry map checks that the entire portion of the
table is empty. This includes freeing any empty lower tables that will be
overwritten by an OA. A separate free list is used while checking and
collecting all the empty lower tables so that writing the new entry is
uninterrupted, either the new entry fully writes or nothing changes.

A special fast path for PAGE_SIZE is implemented that does a direct walk
to the leaf level and installs a single entry. This gives ~15% improvement
for iommu_map() when mapping lists of single pages.

This version sits under the iommu_domain_ops as map_pages() but does not
require the external page size calculation. The implementation is actually
map_range() and can do arbitrary ranges, internally handling all the
validation and supporting any arrangment of page sizes. A future series
can optimize iommu_map() to take advantage of this.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Tested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

0 files changed, 0 insertions, 0 deletions