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The access object has been used externally by VFIO mdev devices, allowing them to pin/unpin physical pages (via needs_pin_pages). Meanwhile, a racy unmap can occur in this case, so these devices usually implement an unmap handler, invoked by iommufd_access_notify_unmap(). The new HW queue object will need the same pin/unpin feature, although it (unlike the mdev case) wants to reject any unmap attempt, during its life cycle. Instead, it would not implement an unmap handler. Thus, bypass any access->ops->unmap access call when the access is marked as internal. Also, an area being pinned by an internal access should reject any unmap request. This cannot be done inside iommufd_access_notify_unmap() as it's a per-iopt action. Add a "num_locks" counter in the struct iopt_area, set that in iopt_area_add_access() when the caller is an internal access. Link: https://patch.msgid.link/r/6df9a43febf79c0379091ec59747276ce9d2493b.1752126748.git.nicolinc@nvidia.com Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Pranjal Shrivastava <praan@google.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.