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CXL 3.1 Section 3.1.1 states: "A Function on a CXL device must not generate INTx messages if that Function participates in CXL.cache protocol or CXL.mem protocols." The generic CXL memory driver only supports devices which use the CXL.mem protocol. The current driver attempts to allocate MSI/MSI-X vectors in anticipation of their need for mailbox interrupts or event processing. However, the above requirement does not require a device to support interrupts, only that they use MSI/MSI-X. For example, a device may disable mailbox interrupts and either be configured for firmware first or skip event processing and function. Dave Larsen reported that the following Intel / Agilex card does not support interrupts on function 0. CXL: Intel Corporation Device 0ddb (rev 01) (prog-if 10 [CXL Memory Device (CXL 2.x)]) Rather than fail device probe if interrupts are not supported; flag that irqs are not enabled and avoid features which require interrupts. Emit messages appropriate for the situation to aid in debugging should device behavior be unexpected due to a failure to allocate vectors. Note that it is possible for a device to have host based event processing through polling. However, the driver does not support polling and it is not anticipated to be generally required. Leave that functionality to a future patch if such a device comes along. Reported-by: Dave Larsen <davelarsen58@gmail.com> Reviewed-by: Dave Jiang <dave.jiang@intel.com> Reviewed-by: Fan Ni <fan.ni@samsung.com> Signed-off-by: Ira Weiny <ira.weiny@intel.com> Reviewed-and-tested-by: Davidlohr Bueso <dave@stgolabs.net> Link: https://lore.kernel.org/r/20240117-dont-fail-irq-v2-1-f33f26b0e365@intel.com Signed-off-by: Dan Williams <dan.j.williams@intel.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.