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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 186 deletions

diff --git a/arch/ia64/mm/hugetlbpage.c b/arch/ia64/mm/hugetlbpage.c
deleted file mode 100644
index adc49f2d22e8..000000000000
--- a/arch/ia64/mm/hugetlbpage.c
+++ /dev/null
@@ -1,186 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * IA-64 Huge TLB Page Support for Kernel.
- *
- * Copyright (C) 2002-2004 Rohit Seth <rohit.seth@intel.com>
- * Copyright (C) 2003-2004 Ken Chen <kenneth.w.chen@intel.com>
- *
- * Sep, 2003: add numa support
- * Feb, 2004: dynamic hugetlb page size via boot parameter
- */
-
-#include <linux/init.h>
-#include <linux/fs.h>
-#include <linux/mm.h>
-#include <linux/hugetlb.h>
-#include <linux/pagemap.h>
-#include <linux/module.h>
-#include <linux/sysctl.h>
-#include <linux/log2.h>
-#include <asm/mman.h>
-#include <asm/tlb.h>
-#include <asm/tlbflush.h>
-
-unsigned int hpage_shift = HPAGE_SHIFT_DEFAULT;
-EXPORT_SYMBOL(hpage_shift);
-
-pte_t *
-huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
-	       unsigned long addr, unsigned long sz)
-{
-	unsigned long taddr = htlbpage_to_page(addr);
-	pgd_t *pgd;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte = NULL;
-
-	pgd = pgd_offset(mm, taddr);
-	p4d = p4d_offset(pgd, taddr);
-	pud = pud_alloc(mm, p4d, taddr);
-	if (pud) {
-		pmd = pmd_alloc(mm, pud, taddr);
-		if (pmd)
-			pte = pte_alloc_huge(mm, pmd, taddr);
-	}
-	return pte;
-}
-
-pte_t *
-huge_pte_offset (struct mm_struct *mm, unsigned long addr, unsigned long sz)
-{
-	unsigned long taddr = htlbpage_to_page(addr);
-	pgd_t *pgd;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte = NULL;
-
-	pgd = pgd_offset(mm, taddr);
-	if (pgd_present(*pgd)) {
-		p4d = p4d_offset(pgd, taddr);
-		if (p4d_present(*p4d)) {
-			pud = pud_offset(p4d, taddr);
-			if (pud_present(*pud)) {
-				pmd = pmd_offset(pud, taddr);
-				if (pmd_present(*pmd))
-					pte = pte_offset_huge(pmd, taddr);
-			}
-		}
-	}
-
-	return pte;
-}
-
-#define mk_pte_huge(entry) { pte_val(entry) |= _PAGE_P; }
-
-/*
- * Don't actually need to do any preparation, but need to make sure
- * the address is in the right region.
- */
-int prepare_hugepage_range(struct file *file,
-			unsigned long addr, unsigned long len)
-{
-	if (len & ~HPAGE_MASK)
-		return -EINVAL;
-	if (addr & ~HPAGE_MASK)
-		return -EINVAL;
-	if (REGION_NUMBER(addr) != RGN_HPAGE)
-		return -EINVAL;
-
-	return 0;
-}
-
-int pmd_huge(pmd_t pmd)
-{
-	return 0;
-}
-
-int pud_huge(pud_t pud)
-{
-	return 0;
-}
-
-void hugetlb_free_pgd_range(struct mmu_gather *tlb,
-			unsigned long addr, unsigned long end,
-			unsigned long floor, unsigned long ceiling)
-{
-	/*
-	 * This is called to free hugetlb page tables.
-	 *
-	 * The offset of these addresses from the base of the hugetlb
-	 * region must be scaled down by HPAGE_SIZE/PAGE_SIZE so that
-	 * the standard free_pgd_range will free the right page tables.
-	 *
-	 * If floor and ceiling are also in the hugetlb region, they
-	 * must likewise be scaled down; but if outside, left unchanged.
-	 */
-
-	addr = htlbpage_to_page(addr);
-	end  = htlbpage_to_page(end);
-	if (REGION_NUMBER(floor) == RGN_HPAGE)
-		floor = htlbpage_to_page(floor);
-	if (REGION_NUMBER(ceiling) == RGN_HPAGE)
-		ceiling = htlbpage_to_page(ceiling);
-
-	free_pgd_range(tlb, addr, end, floor, ceiling);
-}
-
-unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
-		unsigned long pgoff, unsigned long flags)
-{
-	struct vm_unmapped_area_info info;
-
-	if (len > RGN_MAP_LIMIT)
-		return -ENOMEM;
-	if (len & ~HPAGE_MASK)
-		return -EINVAL;
-
-	/* Handle MAP_FIXED */
-	if (flags & MAP_FIXED) {
-		if (prepare_hugepage_range(file, addr, len))
-			return -EINVAL;
-		return addr;
-	}
-
-	/* This code assumes that RGN_HPAGE != 0. */
-	if ((REGION_NUMBER(addr) != RGN_HPAGE) || (addr & (HPAGE_SIZE - 1)))
-		addr = HPAGE_REGION_BASE;
-
-	info.flags = 0;
-	info.length = len;
-	info.low_limit = addr;
-	info.high_limit = HPAGE_REGION_BASE + RGN_MAP_LIMIT;
-	info.align_mask = PAGE_MASK & (HPAGE_SIZE - 1);
-	info.align_offset = 0;
-	return vm_unmapped_area(&info);
-}
-
-static int __init hugetlb_setup_sz(char *str)
-{
-	u64 tr_pages;
-	unsigned long long size;
-
-	if (ia64_pal_vm_page_size(&tr_pages, NULL) != 0)
-		/*
-		 * shouldn't happen, but just in case.
-		 */
-		tr_pages = 0x15557000UL;
-
-	size = memparse(str, &str);
-	if (*str || !is_power_of_2(size) || !(tr_pages & size) ||
-		size <= PAGE_SIZE ||
-		size > (1UL << PAGE_SHIFT << MAX_ORDER)) {
-		printk(KERN_WARNING "Invalid huge page size specified\n");
-		return 1;
-	}
-
-	hpage_shift = __ffs(size);
-	/*
-	 * boot cpu already executed ia64_mmu_init, and has HPAGE_SHIFT_DEFAULT
-	 * override here with new page shift.
-	 */
-	ia64_set_rr(HPAGE_REGION_BASE, hpage_shift << 2);
-	return 0;
-}
-early_param("hugepagesz", hugetlb_setup_sz);