Bug#1021998: linux: please enable CXL_BUS

[Adam Borowski <kilobyte@angband.pl>]

Source: linux
Version: 6.0.2-1
Severity: wishlist

Hi!
Please enable the CXL bus in our kernel configs; its hardware is still rare
(requires PCIe 5.0) but will be widespread well before Bookworm release.

Note that there's some confusion between CXL bus and OpenCAPI OCXL, the
latter being an old IBM thingy from POWER8 times.  Both are PCIe based
and both allow coherent memory attach; IBM has moved to the new protocol
for new hardware.  The old thing has CONFIG_CXL_BASE and CONFIG_CXL.

It's already enabled in Fedora and Ubuntu configs; the former uses a mix
of =y and =m -- but I assume you're going to go all-modular.  Thus:

CONFIG_CXL_BUS=m
CONFIG_CXL_PCI=m
# CONFIG_CXL_MEM_RAW_COMMANDS=n
CONFIG_CXL_ACPI=m
CONFIG_CXL_PMEM=m
CONFIG_CXL_MEM=m
CONFIG_CXL_PORT=m
CONFIG_CXL_SUSPEND=y
CONFIG_CXL_REGION=m

(Raw commands are a debug only interface.)

I see that Ubuntu disables CONFIG_CXL_BUS (ie, everything) on s390x as that
arch is only VM guests that can't manage their own memory; I have no clue
about our weirder architectures.  But at least amd64 arm64 riscv64 ppc64el
want CXL_BUS enabled.


Meow!