linux/lib/xz/Kconfig
Ard Biesheuvel cf8e865810 arch: Remove Itanium (IA-64) architecture
The Itanium architecture is obsolete, and an informal survey [0] reveals
that any residual use of Itanium hardware in production is mostly HP-UX
or OpenVMS based. The use of Linux on Itanium appears to be limited to
enthusiasts that occasionally boot a fresh Linux kernel to see whether
things are still working as intended, and perhaps to churn out some
distro packages that are rarely used in practice.

None of the original companies behind Itanium still produce or support
any hardware or software for the architecture, and it is listed as
'Orphaned' in the MAINTAINERS file, as apparently, none of the engineers
that contributed on behalf of those companies (nor anyone else, for that
matter) have been willing to support or maintain the architecture
upstream or even be responsible for applying the odd fix. The Intel
firmware team removed all IA-64 support from the Tianocore/EDK2
reference implementation of EFI in 2018. (Itanium is the original
architecture for which EFI was developed, and the way Linux supports it
deviates significantly from other architectures.) Some distros, such as
Debian and Gentoo, still maintain [unofficial] ia64 ports, but many have
dropped support years ago.

While the argument is being made [1] that there is a 'for the common
good' angle to being able to build and run existing projects such as the
Grid Community Toolkit [2] on Itanium for interoperability testing, the
fact remains that none of those projects are known to be deployed on
Linux/ia64, and very few people actually have access to such a system in
the first place. Even if there were ways imaginable in which Linux/ia64
could be put to good use today, what matters is whether anyone is
actually doing that, and this does not appear to be the case.

There are no emulators widely available, and so boot testing Itanium is
generally infeasible for ordinary contributors. GCC still supports IA-64
but its compile farm [3] no longer has any IA-64 machines. GLIBC would
like to get rid of IA-64 [4] too because it would permit some overdue
code cleanups. In summary, the benefits to the ecosystem of having IA-64
be part of it are mostly theoretical, whereas the maintenance overhead
of keeping it supported is real.

So let's rip off the band aid, and remove the IA-64 arch code entirely.
This follows the timeline proposed by the Debian/ia64 maintainer [5],
which removes support in a controlled manner, leaving IA-64 in a known
good state in the most recent LTS release. Other projects will follow
once the kernel support is removed.

[0] https://lore.kernel.org/all/CAMj1kXFCMh_578jniKpUtx_j8ByHnt=s7S+yQ+vGbKt9ud7+kQ@mail.gmail.com/
[1] https://lore.kernel.org/all/0075883c-7c51-00f5-2c2d-5119c1820410@web.de/
[2] https://gridcf.org/gct-docs/latest/index.html
[3] https://cfarm.tetaneutral.net/machines/list/
[4] https://lore.kernel.org/all/87bkiilpc4.fsf@mid.deneb.enyo.de/
[5] https://lore.kernel.org/all/ff58a3e76e5102c94bb5946d99187b358def688a.camel@physik.fu-berlin.de/

Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
2023-09-11 08:13:17 +00:00

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# SPDX-License-Identifier: GPL-2.0-only
config XZ_DEC
tristate "XZ decompression support"
select CRC32
help
LZMA2 compression algorithm and BCJ filters are supported using
the .xz file format as the container. For integrity checking,
CRC32 is supported. See Documentation/staging/xz.rst for more information.
if XZ_DEC
config XZ_DEC_X86
bool "x86 BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_POWERPC
bool "PowerPC BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_ARM
bool "ARM BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_ARMTHUMB
bool "ARM-Thumb BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_SPARC
bool "SPARC BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_MICROLZMA
bool "MicroLZMA decoder"
default n
help
MicroLZMA is a header format variant where the first byte
of a raw LZMA stream (without the end of stream marker) has
been replaced with a bitwise-negation of the lc/lp/pb
properties byte. MicroLZMA was created to be used in EROFS
but can be used by other things too where wasting minimal
amount of space for headers is important.
Unless you know that you need this, say N.
endif
config XZ_DEC_BCJ
bool
default n
config XZ_DEC_TEST
tristate "XZ decompressor tester"
default n
depends on XZ_DEC
help
This allows passing .xz files to the in-kernel XZ decoder via
a character special file. It calculates CRC32 of the decompressed
data and writes diagnostics to the system log.
Unless you are developing the XZ decoder, you don't need this
and should say N.