iommufd: Iterate the cache invalidation array in the core

The cache invalidation ops, cache_invalidate_user() for a nested HWPT and
the cache_invalidate() for a vIOMMU, are each handed the full user request
array and report how many of the array entries they handled by setting the
array->entry_num. Every driver therefore implements its own loop over the
array, and a driver wanting to process that array in fixed-size chunks
(e.g. to issue commands out of a fixed-size on-stack buffer) has to carry
the loop and its sub-array bookkeeping all on its own.

Move the iteration into the iommufd core instead. Invoke the op with a
sub-array that starts at the first not-yet-handled entry, let it handle a
prefix of that sub-array and report the count via array->entry_num, then
advance the base pointer and re-invoke the op until the entire array has
been consumed or until the op returns an error along the way.

A driver that handles the entire window in one single call, as all of the
current drivers happen to do, finishes the loop in just one pass, so this
does not change any of the existing behavior. It instead lets each of the
drivers convert to bounded chunk processing on its own, done by each of the
subsequent changes.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Link: https://patch.msgid.link/e1896d79382392f8a0bf0ae736aa295f11c45ef0.1788127877.git.nicolinc@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

0 files changed, 0 insertions, 0 deletions