Micron CXL Kernel Readme
========================

* This is the "cxl3" kernel from November 2021
* Security is disabled
* Raw mailbox ioctl commands are enabled
* ("normal" mailbox command ioctls also work)
* There is an example program that issues mailbox commands
  in the cxl-tools repo at progs/cxl_ioctl.c
  (see https://bitbucket.micron.com/bbdc/projects/SBUSW/repos/cxl-tools/browse)
* Note that building cxl components as modules is not working - at least the
  cxl_pci module (where the mbox interface lives) currently will not compile
  as a module. This is not related to any Micron patches...

Building
========

An appropriate config file is checked in as config-cxl3.  To build this
kernel, move that to ".config" and build.  E.g.:

    cp config-cxl3 .config
    make [-j24]


Installing
==========

To install on a system or VM:

    make modules_install headers_install install

Important note: You don't have to build this kernel on the system where you
intend to install it, but the directory that you install it from must be the same
path as it was built at.  I don't know why this limitation exists.  This might
force you to need to build the kernel on the target system...

Setting Default Kernel
======================

    grubby --set-default=/boot/<kernel>

Where <kernel> is the kernel file you want to activate as the default
(e.g. vmlinuz-5.15.0-rc2-cxl3+)

Debugging
=========

The driver contains debug messages (added by Micron) to assist in
trouble shooting the mailbox ioctl interface.

To enable kernel debug messages:

    sudo echo 'file drivers/cxl/pci.c +p'>/sys/kernel/debug/dynamic_debug/control

Tailing Kernel Logs
===================

To put a "tail" on the kernel log, including cxl-related debug messages
(if enabled), do this:

    journalctl -k -p 7 -f

To view the kernel log from the previous boot (in case you crashed it trying
something that didn't work), do this

    journalctl -k -b -1  # and then go to the end of the buffer in "less"

End Micron CXL Notes
====================

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.