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The upcoming mechanism to allocate MSI-X vectors after enabling MSI-X needs
to share some of the MSI-X descriptor setup.
The regular descriptor setup on enable has the following code flow:
1) Allocate descriptor
2) Setup descriptor with PCI specific data
3) Insert descriptor
4) Allocate interrupts which in turn scans the inserted
descriptors
This cannot be easily changed because the PCI/MSI code needs to handle the
legacy architecture specific allocation model and the irq domain model
where quite some domains have the assumption that the above flow is how it
works.
Ideally the code flow should look like this:
1) Invoke allocation at the MSI core
2) MSI core allocates descriptor
3) MSI core calls back into the irq domain which fills in
the domain specific parts
This could be done for underlying parent MSI domains which support
post-enable allocation/free but that would create significantly different
code pathes for MSI/MSI-X enable.
Though for dynamic allocation which wants to share the allocation code with
the upcoming PCI/IMS support it's the right thing to do.
Split the MSI-X descriptor setup into the preallocation part which just sets
the index and fills in the horrible hack of virtual IRQs and the real PCI
specific MSI-X setup part which solely depends on the index in the
descriptor. This allows to provide a common dynamic allocation interface at
the MSI core level for both PCI/MSI-X and PCI/IMS.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221124232326.616292598@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.