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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 128 deletions

diff --git a/arch/ia64/include/asm/tlbflush.h b/arch/ia64/include/asm/tlbflush.h
deleted file mode 100644
index ceac10c4d6e2..000000000000
--- a/arch/ia64/include/asm/tlbflush.h
+++ /dev/null
@@ -1,128 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_IA64_TLBFLUSH_H
-#define _ASM_IA64_TLBFLUSH_H
-
-/*
- * Copyright (C) 2002 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- */
-
-
-#include <linux/mm.h>
-
-#include <asm/intrinsics.h>
-#include <asm/mmu_context.h>
-#include <asm/page.h>
-
-struct ia64_tr_entry {
-	u64 ifa;
-	u64 itir;
-	u64 pte;
-	u64 rr;
-}; /*Record for tr entry!*/
-
-extern int ia64_itr_entry(u64 target_mask, u64 va, u64 pte, u64 log_size);
-extern void ia64_ptr_entry(u64 target_mask, int slot);
-extern struct ia64_tr_entry *ia64_idtrs[NR_CPUS];
-
-/*
- region register macros
-*/
-#define RR_TO_VE(val)   (((val) >> 0) & 0x0000000000000001)
-#define RR_VE(val)     (((val) & 0x0000000000000001) << 0)
-#define RR_VE_MASK     0x0000000000000001L
-#define RR_VE_SHIFT    0
-#define RR_TO_PS(val)  (((val) >> 2) & 0x000000000000003f)
-#define RR_PS(val)     (((val) & 0x000000000000003f) << 2)
-#define RR_PS_MASK     0x00000000000000fcL
-#define RR_PS_SHIFT    2
-#define RR_RID_MASK    0x00000000ffffff00L
-#define RR_TO_RID(val)         ((val >> 8) & 0xffffff)
-
-/*
- * Now for some TLB flushing routines.  This is the kind of stuff that
- * can be very expensive, so try to avoid them whenever possible.
- */
-extern void setup_ptcg_sem(int max_purges, int from_palo);
-
-/*
- * Flush everything (kernel mapping may also have changed due to
- * vmalloc/vfree).
- */
-extern void local_flush_tlb_all (void);
-
-#ifdef CONFIG_SMP
-  extern void smp_flush_tlb_all (void);
-  extern void smp_flush_tlb_mm (struct mm_struct *mm);
-  extern void smp_flush_tlb_cpumask (cpumask_t xcpumask);
-# define flush_tlb_all()	smp_flush_tlb_all()
-#else
-# define flush_tlb_all()	local_flush_tlb_all()
-# define smp_flush_tlb_cpumask(m) local_flush_tlb_all()
-#endif
-
-static inline void
-local_finish_flush_tlb_mm (struct mm_struct *mm)
-{
-	if (mm == current->active_mm)
-		activate_context(mm);
-}
-
-/*
- * Flush a specified user mapping.  This is called, e.g., as a result of fork() and
- * exit().  fork() ends up here because the copy-on-write mechanism needs to write-protect
- * the PTEs of the parent task.
- */
-static inline void
-flush_tlb_mm (struct mm_struct *mm)
-{
-	if (!mm)
-		return;
-
-	set_bit(mm->context, ia64_ctx.flushmap);
-	mm->context = 0;
-
-	if (atomic_read(&mm->mm_users) == 0)
-		return;		/* happens as a result of exit_mmap() */
-
-#ifdef CONFIG_SMP
-	smp_flush_tlb_mm(mm);
-#else
-	local_finish_flush_tlb_mm(mm);
-#endif
-}
-
-extern void flush_tlb_range (struct vm_area_struct *vma, unsigned long start, unsigned long end);
-
-/*
- * Page-granular tlb flush.
- */
-static inline void
-flush_tlb_page (struct vm_area_struct *vma, unsigned long addr)
-{
-#ifdef CONFIG_SMP
-	flush_tlb_range(vma, (addr & PAGE_MASK), (addr & PAGE_MASK) + PAGE_SIZE);
-#else
-	if (vma->vm_mm == current->active_mm)
-		ia64_ptcl(addr, (PAGE_SHIFT << 2));
-	else
-		vma->vm_mm->context = 0;
-#endif
-}
-
-/*
- * Flush the local TLB. Invoked from another cpu using an IPI.
- */
-#ifdef CONFIG_SMP
-void smp_local_flush_tlb(void);
-#else
-#define smp_local_flush_tlb()
-#endif
-
-static inline void flush_tlb_kernel_range(unsigned long start,
-					  unsigned long end)
-{
-	flush_tlb_all();	/* XXX fix me */
-}
-
-#endif /* _ASM_IA64_TLBFLUSH_H */