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The Itanium architecture is obsolete, and an informal survey [0] reveals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>

1 files changed, 0 insertions, 55 deletions

diff --git a/arch/ia64/Kconfig.debug b/arch/ia64/Kconfig.debug
deleted file mode 100644
index 2ce008e2d164..000000000000
--- a/arch/ia64/Kconfig.debug
+++ /dev/null
@@ -1,55 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-
-choice
-	prompt "Physical memory granularity"
-	default IA64_GRANULE_64MB
-
-config IA64_GRANULE_16MB
-	bool "16MB"
-	help
-	  IA-64 identity-mapped regions use a large page size called "granules".
-
-	  Select "16MB" for a small granule size.
-	  Select "64MB" for a large granule size.  This is the current default.
-
-config IA64_GRANULE_64MB
-	bool "64MB"
-	depends on BROKEN
-
-endchoice
-
-config IA64_PRINT_HAZARDS
-	bool "Print possible IA-64 dependency violations to console"
-	depends on DEBUG_KERNEL
-	help
-	  Selecting this option prints more information for Illegal Dependency
-	  Faults, that is, for Read-after-Write (RAW), Write-after-Write (WAW),
-	  or Write-after-Read (WAR) violations.  This option is ignored if you
-	  are compiling for an Itanium A step processor
-	  (CONFIG_ITANIUM_ASTEP_SPECIFIC).  If you're unsure, select Y.
-
-config DISABLE_VHPT
-	bool "Disable VHPT"
-	depends on DEBUG_KERNEL
-	help
-	  The Virtual Hash Page Table (VHPT) enhances virtual address
-	  translation performance.  Normally you want the VHPT active but you
-	  can select this option to disable the VHPT for debugging.  If you're
-	  unsure, answer N.
-
-config IA64_DEBUG_CMPXCHG
-	bool "Turn on compare-and-exchange bug checking (slow!)"
-	depends on DEBUG_KERNEL && PRINTK
-	help
-	  Selecting this option turns on bug checking for the IA-64
-	  compare-and-exchange instructions.  This is slow!  Itaniums
-	  from step B3 or later don't have this problem. If you're unsure,
-	  select N.
-
-config IA64_DEBUG_IRQ
-	bool "Turn on irq debug checks (slow!)"
-	depends on DEBUG_KERNEL
-	help
-	  Selecting this option turns on bug checking for the IA-64 irq_save
-	  and restore instructions.  It's useful for tracking down spinlock
-	  problems, but slow!  If you're unsure, select N.