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The new PCI/IMS (Interrupt Message Store) functionality is allowing
hardware vendors to provide implementation specific storage for the MSI
messages. This can be device memory and also host/guest memory, e.g. in
queue memory which is shared with the hardware.
This requires device specific MSI interrupt domains, which cannot be
achieved by expanding the existing PCI/MSI interrupt domain concept which is
a global interrupt domain shared by all PCI devices on a particular (IOMMU)
segment:
|--- device 1
[Vector]---[Remapping]---[PCI/MSI]--|...
|--- device N
This works because the PCI/MSI[-X] space is uniform, but falls apart with
PCI/IMS which is implementation defined and must be available along with
PCI/MSI[-X] on the same device.
To support PCI/MSI[-X] plus PCI/IMS on the same device it is required to
rework the PCI/MSI interrupt domain hierarchy concept in the following way:
|--- [PCI/MSI] device 1
[Vector]---[Remapping]---|...
|--- [PCI/MSI] device N
That allows in the next step to create multiple interrupt domains per device:
|--- [PCI/MSI] device 1
|--- [PCI/IMS] device 1
[Vector]---[Remapping]---|...
|--- [PCI/MSI] device N
|--- [PCI/IMS] device N
So the domain which previously created the global PCI/MSI domain must now
act as parent domain for the per device domains.
The hierarchy depth is the same as before, but the PCI/MSI domains are then
device specific and not longer global.
Provide IRQ_DOMAIN_FLAG_MSI_PARENT, which allows to identify these parent
domains, along with helpers to query it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221124230313.690038274@linutronix.de
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.