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When an MSI doorbell is located downstream of an IOMMU, it is required to swizzle the physical address with an appropriately-mapped IOVA for any device attached to one of our DMA ops domain. At the moment, the allocation of the mapping may be done when composing the message. However, the composing may be done in non-preemtible context while the allocation requires to be called from preemptible context. A follow-up change will split the current logic in two functions requiring to keep an IOMMU cookie per MSI. A new field is introduced in msi_desc to store an IOMMU cookie. As the cookie may not be required in some configuration, the field is protected under a new config CONFIG_IRQ_MSI_IOMMU. A pair of helpers has also been introduced to access the field. Signed-off-by: Julien Grall <julien.grall@arm.com> Reviewed-by: Robin Murphy <robin.murphy@arm.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.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 Restructured Text 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.