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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 83 deletions

diff --git a/arch/ia64/kernel/entry.h b/arch/ia64/kernel/entry.h
deleted file mode 100644
index 6463dc316263..000000000000
--- a/arch/ia64/kernel/entry.h
+++ /dev/null
@@ -1,83 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-/*
- * Preserved registers that are shared between code in ivt.S and
- * entry.S.  Be careful not to step on these!
- */
-#define PRED_LEAVE_SYSCALL	1 /* TRUE iff leave from syscall */
-#define PRED_KERNEL_STACK	2 /* returning to kernel-stacks? */
-#define PRED_USER_STACK		3 /* returning to user-stacks? */
-#define PRED_SYSCALL		4 /* inside a system call? */
-#define PRED_NON_SYSCALL	5 /* complement of PRED_SYSCALL */
-
-#ifdef __ASSEMBLY__
-# define PASTE2(x,y)	x##y
-# define PASTE(x,y)	PASTE2(x,y)
-
-# define pLvSys		PASTE(p,PRED_LEAVE_SYSCALL)
-# define pKStk		PASTE(p,PRED_KERNEL_STACK)
-# define pUStk		PASTE(p,PRED_USER_STACK)
-# define pSys		PASTE(p,PRED_SYSCALL)
-# define pNonSys	PASTE(p,PRED_NON_SYSCALL)
-#endif
-
-#define PT(f)		(IA64_PT_REGS_##f##_OFFSET)
-#define SW(f)		(IA64_SWITCH_STACK_##f##_OFFSET)
-#define SOS(f)		(IA64_SAL_OS_STATE_##f##_OFFSET)
-
-#define PT_REGS_SAVES(off)			\
-	.unwabi 3, 'i';				\
-	.fframe IA64_PT_REGS_SIZE+16+(off);	\
-	.spillsp rp, PT(CR_IIP)+16+(off);	\
-	.spillsp ar.pfs, PT(CR_IFS)+16+(off);	\
-	.spillsp ar.unat, PT(AR_UNAT)+16+(off);	\
-	.spillsp ar.fpsr, PT(AR_FPSR)+16+(off);	\
-	.spillsp pr, PT(PR)+16+(off);
-
-#define PT_REGS_UNWIND_INFO(off)		\
-	.prologue;				\
-	PT_REGS_SAVES(off);			\
-	.body
-
-#define SWITCH_STACK_SAVES(off)							\
-	.savesp ar.unat,SW(CALLER_UNAT)+16+(off);				\
-	.savesp ar.fpsr,SW(AR_FPSR)+16+(off);					\
-	.spillsp f2,SW(F2)+16+(off); .spillsp f3,SW(F3)+16+(off);		\
-	.spillsp f4,SW(F4)+16+(off); .spillsp f5,SW(F5)+16+(off);		\
-	.spillsp f16,SW(F16)+16+(off); .spillsp f17,SW(F17)+16+(off);		\
-	.spillsp f18,SW(F18)+16+(off); .spillsp f19,SW(F19)+16+(off);		\
-	.spillsp f20,SW(F20)+16+(off); .spillsp f21,SW(F21)+16+(off);		\
-	.spillsp f22,SW(F22)+16+(off); .spillsp f23,SW(F23)+16+(off);		\
-	.spillsp f24,SW(F24)+16+(off); .spillsp f25,SW(F25)+16+(off);		\
-	.spillsp f26,SW(F26)+16+(off); .spillsp f27,SW(F27)+16+(off);		\
-	.spillsp f28,SW(F28)+16+(off); .spillsp f29,SW(F29)+16+(off);		\
-	.spillsp f30,SW(F30)+16+(off); .spillsp f31,SW(F31)+16+(off);		\
-	.spillsp r4,SW(R4)+16+(off); .spillsp r5,SW(R5)+16+(off);		\
-	.spillsp r6,SW(R6)+16+(off); .spillsp r7,SW(R7)+16+(off);		\
-	.spillsp b0,SW(B0)+16+(off); .spillsp b1,SW(B1)+16+(off);		\
-	.spillsp b2,SW(B2)+16+(off); .spillsp b3,SW(B3)+16+(off);		\
-	.spillsp b4,SW(B4)+16+(off); .spillsp b5,SW(B5)+16+(off);		\
-	.spillsp ar.pfs,SW(AR_PFS)+16+(off); .spillsp ar.lc,SW(AR_LC)+16+(off);	\
-	.spillsp @priunat,SW(AR_UNAT)+16+(off);					\
-	.spillsp ar.rnat,SW(AR_RNAT)+16+(off);					\
-	.spillsp ar.bspstore,SW(AR_BSPSTORE)+16+(off);				\
-	.spillsp pr,SW(PR)+16+(off)
-
-#define DO_SAVE_SWITCH_STACK			\
-	movl r28=1f;				\
-	;;					\
-	.fframe IA64_SWITCH_STACK_SIZE;		\
-	adds sp=-IA64_SWITCH_STACK_SIZE,sp;	\
-	mov.ret.sptk b7=r28,1f;			\
-	SWITCH_STACK_SAVES(0);			\
-	br.cond.sptk.many save_switch_stack;	\
-1:
-
-#define DO_LOAD_SWITCH_STACK			\
-	movl r28=1f;				\
-	;;					\
-	invala;					\
-	mov.ret.sptk b7=r28,1f;			\
-	br.cond.sptk.many load_switch_stack;	\
-1:	.restore sp;				\
-	adds sp=IA64_SWITCH_STACK_SIZE,sp