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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 53 deletions

diff --git a/arch/ia64/include/asm/percpu.h b/arch/ia64/include/asm/percpu.h
deleted file mode 100644
index f357b9bb3576..000000000000
--- a/arch/ia64/include/asm/percpu.h
+++ /dev/null
@@ -1,53 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_IA64_PERCPU_H
-#define _ASM_IA64_PERCPU_H
-
-/*
- * Copyright (C) 2002-2003 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- */
-
-#ifdef __ASSEMBLY__
-# define THIS_CPU(var)	(var)  /* use this to mark accesses to per-CPU variables... */
-#else /* !__ASSEMBLY__ */
-
-
-#include <linux/threads.h>
-
-#ifdef CONFIG_SMP
-
-#ifdef HAVE_MODEL_SMALL_ATTRIBUTE
-# define PER_CPU_ATTRIBUTES	__attribute__((__model__ (__small__)))
-#endif
-
-#define __my_cpu_offset	__ia64_per_cpu_var(local_per_cpu_offset)
-
-extern void *per_cpu_init(void);
-
-#else /* ! SMP */
-
-#define per_cpu_init()				(__phys_per_cpu_start)
-
-#endif	/* SMP */
-
-#define PER_CPU_BASE_SECTION ".data..percpu"
-
-/*
- * Be extremely careful when taking the address of this variable!  Due to virtual
- * remapping, it is different from the canonical address returned by this_cpu_ptr(&var)!
- * On the positive side, using __ia64_per_cpu_var() instead of this_cpu_ptr() is slightly
- * more efficient.
- */
-#define __ia64_per_cpu_var(var) (*({					\
-	__verify_pcpu_ptr(&(var));					\
-	((typeof(var) __kernel __force *)&(var));			\
-}))
-
-#include <asm-generic/percpu.h>
-
-/* Equal to __per_cpu_offset[smp_processor_id()], but faster to access: */
-DECLARE_PER_CPU(unsigned long, local_per_cpu_offset);
-
-#endif /* !__ASSEMBLY__ */
-
-#endif /* _ASM_IA64_PERCPU_H */