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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 110 deletions

diff --git a/arch/ia64/include/asm/acpi.h b/arch/ia64/include/asm/acpi.h
deleted file mode 100644
index 58500a964238..000000000000
--- a/arch/ia64/include/asm/acpi.h
+++ /dev/null
@@ -1,110 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-/*
- *  Copyright (C) 1999 VA Linux Systems
- *  Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
- *  Copyright (C) 2000,2001 J.I. Lee <jung-ik.lee@intel.com>
- *  Copyright (C) 2001,2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
- */
-
-#ifndef _ASM_ACPI_H
-#define _ASM_ACPI_H
-
-#ifdef __KERNEL__
-
-#include <acpi/proc_cap_intel.h>
-
-#include <linux/init.h>
-#include <linux/numa.h>
-#include <asm/numa.h>
-
-
-extern int acpi_lapic;
-#define acpi_disabled 0	/* ACPI always enabled on IA64 */
-#define acpi_noirq 0	/* ACPI always enabled on IA64 */
-#define acpi_pci_disabled 0 /* ACPI PCI always enabled on IA64 */
-#define acpi_strict 1	/* no ACPI spec workarounds on IA64 */
-
-static inline bool acpi_has_cpu_in_madt(void)
-{
-	return !!acpi_lapic;
-}
-
-#define acpi_processor_cstate_check(x) (x) /* no idle limits on IA64 :) */
-static inline void disable_acpi(void) { }
-
-int acpi_request_vector (u32 int_type);
-int acpi_gsi_to_irq (u32 gsi, unsigned int *irq);
-
-/* Low-level suspend routine. */
-extern int acpi_suspend_lowlevel(void);
-
-static inline unsigned long acpi_get_wakeup_address(void)
-{
-	return 0;
-}
-
-/*
- * Record the cpei override flag and current logical cpu. This is
- * useful for CPU removal.
- */
-extern unsigned int can_cpei_retarget(void);
-extern unsigned int is_cpu_cpei_target(unsigned int cpu);
-extern void set_cpei_target_cpu(unsigned int cpu);
-extern unsigned int get_cpei_target_cpu(void);
-extern void prefill_possible_map(void);
-#ifdef CONFIG_ACPI_HOTPLUG_CPU
-extern int additional_cpus;
-#else
-#define additional_cpus 0
-#endif
-
-#ifdef CONFIG_ACPI_NUMA
-#if MAX_NUMNODES > 256
-#define MAX_PXM_DOMAINS MAX_NUMNODES
-#else
-#define MAX_PXM_DOMAINS (256)
-#endif
-extern int pxm_to_nid_map[MAX_PXM_DOMAINS];
-extern int __initdata nid_to_pxm_map[MAX_NUMNODES];
-#endif
-
-static inline bool arch_has_acpi_pdc(void) { return true; }
-static inline void arch_acpi_set_proc_cap_bits(u32 *cap)
-{
-	*cap |= ACPI_PROC_CAP_EST_CAPABILITY_SMP;
-}
-
-#ifdef CONFIG_ACPI_NUMA
-extern cpumask_t early_cpu_possible_map;
-#define for_each_possible_early_cpu(cpu)  \
-	for_each_cpu((cpu), &early_cpu_possible_map)
-
-static inline void per_cpu_scan_finalize(int min_cpus, int reserve_cpus)
-{
-	int low_cpu, high_cpu;
-	int cpu;
-	int next_nid = 0;
-
-	low_cpu = cpumask_weight(&early_cpu_possible_map);
-
-	high_cpu = max(low_cpu, min_cpus);
-	high_cpu = min(high_cpu + reserve_cpus, NR_CPUS);
-
-	for (cpu = low_cpu; cpu < high_cpu; cpu++) {
-		cpumask_set_cpu(cpu, &early_cpu_possible_map);
-		if (node_cpuid[cpu].nid == NUMA_NO_NODE) {
-			node_cpuid[cpu].nid = next_nid;
-			next_nid++;
-			if (next_nid >= num_online_nodes())
-				next_nid = 0;
-		}
-	}
-}
-
-extern void acpi_numa_fixup(void);
-
-#endif /* CONFIG_ACPI_NUMA */
-
-#endif /*__KERNEL__*/
-
-#endif /*_ASM_ACPI_H*/