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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 138 deletions

diff --git a/arch/ia64/include/uapi/asm/cmpxchg.h b/arch/ia64/include/uapi/asm/cmpxchg.h
deleted file mode 100644
index a59b5de6eec6..000000000000
--- a/arch/ia64/include/uapi/asm/cmpxchg.h
+++ /dev/null
@@ -1,138 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
-#ifndef _UAPI_ASM_IA64_CMPXCHG_H
-#define _UAPI_ASM_IA64_CMPXCHG_H
-
-/*
- * Compare/Exchange, forked from asm/intrinsics.h
- * which was:
- *
- *	Copyright (C) 2002-2003 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- */
-
-#ifndef __ASSEMBLY__
-
-#include <linux/types.h>
-/* include compiler specific intrinsics */
-#include <asm/ia64regs.h>
-#include <asm/gcc_intrin.h>
-
-/*
- * This function doesn't exist, so you'll get a linker error if
- * something tries to do an invalid xchg().
- */
-extern void ia64_xchg_called_with_bad_pointer(void);
-
-#define __arch_xchg(x, ptr, size)					\
-({									\
-	unsigned long __xchg_result;					\
-									\
-	switch (size) {							\
-	case 1:								\
-		__xchg_result = ia64_xchg1((__u8 __force *)ptr, x);	\
-		break;							\
-									\
-	case 2:								\
-		__xchg_result = ia64_xchg2((__u16 __force *)ptr, x);	\
-		break;							\
-									\
-	case 4:								\
-		__xchg_result = ia64_xchg4((__u32 __force *)ptr, x);	\
-		break;							\
-									\
-	case 8:								\
-		__xchg_result = ia64_xchg8((__u64 __force *)ptr, x);	\
-		break;							\
-	default:							\
-		ia64_xchg_called_with_bad_pointer();			\
-	}								\
-	(__typeof__ (*(ptr)) __force) __xchg_result;			\
-})
-
-#ifndef __KERNEL__
-#define xchg(ptr, x)							\
-({(__typeof__(*(ptr))) __arch_xchg((unsigned long) (x), (ptr), sizeof(*(ptr)));})
-#endif
-
-/*
- * Atomic compare and exchange.  Compare OLD with MEM, if identical,
- * store NEW in MEM.  Return the initial value in MEM.  Success is
- * indicated by comparing RETURN with OLD.
- */
-
-/*
- * This function doesn't exist, so you'll get a linker error
- * if something tries to do an invalid cmpxchg().
- */
-extern long ia64_cmpxchg_called_with_bad_pointer(void);
-
-#define ia64_cmpxchg(sem, ptr, old, new, size)				\
-({									\
-	__u64 _o_, _r_;							\
-									\
-	switch (size) {							\
-	case 1:								\
-		_o_ = (__u8) (long __force) (old);			\
-		break;							\
-	case 2:								\
-		_o_ = (__u16) (long __force) (old);			\
-		break;							\
-	case 4:								\
-		_o_ = (__u32) (long __force) (old);			\
-		break;							\
-	case 8:								\
-		_o_ = (__u64) (long __force) (old);			\
-		break;							\
-	default:							\
-		break;							\
-	}								\
-	switch (size) {							\
-	case 1:								\
-		_r_ = ia64_cmpxchg1_##sem((__u8 __force *) ptr, new, _o_);	\
-		break;							\
-									\
-	case 2:								\
-		_r_ = ia64_cmpxchg2_##sem((__u16 __force *) ptr, new, _o_);	\
-		break;							\
-									\
-	case 4:								\
-		_r_ = ia64_cmpxchg4_##sem((__u32 __force *) ptr, new, _o_);	\
-		break;							\
-									\
-	case 8:								\
-		_r_ = ia64_cmpxchg8_##sem((__u64 __force *) ptr, new, _o_);	\
-		break;							\
-									\
-	default:							\
-		_r_ = ia64_cmpxchg_called_with_bad_pointer();		\
-		break;							\
-	}								\
-	(__typeof__(old) __force) _r_;					\
-})
-
-#define cmpxchg_acq(ptr, o, n)	\
-	ia64_cmpxchg(acq, (ptr), (o), (n), sizeof(*(ptr)))
-#define cmpxchg_rel(ptr, o, n)	\
-	ia64_cmpxchg(rel, (ptr), (o), (n), sizeof(*(ptr)))
-
-/*
- * Worse still - early processor implementations actually just ignored
- * the acquire/release and did a full fence all the time.  Unfortunately
- * this meant a lot of badly written code that used .acq when they really
- * wanted .rel became legacy out in the wild - so when we made a cpu
- * that strictly did the .acq or .rel ... all that code started breaking - so
- * we had to back-pedal and keep the "legacy" behavior of a full fence :-(
- */
-
-#ifndef __KERNEL__
-/* for compatibility with other platforms: */
-#define cmpxchg(ptr, o, n)	cmpxchg_acq((ptr), (o), (n))
-#define cmpxchg64(ptr, o, n)	cmpxchg_acq((ptr), (o), (n))
-
-#define cmpxchg_local		cmpxchg
-#define cmpxchg64_local		cmpxchg64
-#endif
-
-#endif /* !__ASSEMBLY__ */
-
-#endif /* _UAPI_ASM_IA64_CMPXCHG_H */