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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 87 deletions

diff --git a/arch/ia64/kernel/efi_stub.S b/arch/ia64/kernel/efi_stub.S
deleted file mode 100644
index 1fd61b78fb29..000000000000
--- a/arch/ia64/kernel/efi_stub.S
+++ /dev/null
@@ -1,87 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * EFI call stub.
- *
- * Copyright (C) 1999-2001 Hewlett-Packard Co
- *	David Mosberger <davidm@hpl.hp.com>
- *
- * This stub allows us to make EFI calls in physical mode with interrupts
- * turned off.  We need this because we can't call SetVirtualMap() until
- * the kernel has booted far enough to allow allocation of struct vm_area_struct
- * entries (which we would need to map stuff with memory attributes other
- * than uncached or writeback...).  Since the GetTime() service gets called
- * earlier than that, we need to be able to make physical mode EFI calls from
- * the kernel.
- */
-
-/*
- * PSR settings as per SAL spec (Chapter 8 in the "IA-64 System
- * Abstraction Layer Specification", revision 2.6e).  Note that
- * psr.dfl and psr.dfh MUST be cleared, despite what this manual says.
- * Otherwise, SAL dies whenever it's trying to do an IA-32 BIOS call
- * (the br.ia instruction fails unless psr.dfl and psr.dfh are
- * cleared).  Fortunately, SAL promises not to touch the floating
- * point regs, so at least we don't have to save f2-f127.
- */
-#define PSR_BITS_TO_CLEAR						\
-	(IA64_PSR_I | IA64_PSR_IT | IA64_PSR_DT | IA64_PSR_RT |		\
-	 IA64_PSR_DD | IA64_PSR_SS | IA64_PSR_RI | IA64_PSR_ED |	\
-	 IA64_PSR_DFL | IA64_PSR_DFH)
-
-#define PSR_BITS_TO_SET							\
-	(IA64_PSR_BN)
-
-#include <asm/processor.h>
-#include <asm/asmmacro.h>
-
-/*
- * Inputs:
- *	in0 = address of function descriptor of EFI routine to call
- *	in1..in7 = arguments to routine
- *
- * Outputs:
- *	r8 = EFI_STATUS returned by called function
- */
-
-GLOBAL_ENTRY(efi_call_phys)
-	.prologue ASM_UNW_PRLG_RP|ASM_UNW_PRLG_PFS, ASM_UNW_PRLG_GRSAVE(8)
-	alloc loc1=ar.pfs,8,7,7,0
-	ld8 r2=[in0],8			// load EFI function's entry point
-	mov loc0=rp
-	.body
-	;;
-	mov loc2=gp			// save global pointer
-	mov loc4=ar.rsc			// save RSE configuration
-	mov ar.rsc=0			// put RSE in enforced lazy, LE mode
-	;;
-	ld8 gp=[in0]			// load EFI function's global pointer
-	movl r16=PSR_BITS_TO_CLEAR
-	mov loc3=psr			// save processor status word
-	movl r17=PSR_BITS_TO_SET
-	;;
-	or loc3=loc3,r17
-	mov b6=r2
-	;;
-	andcm r16=loc3,r16	// get psr with IT, DT, and RT bits cleared
-	br.call.sptk.many rp=ia64_switch_mode_phys
-.ret0:	mov out4=in5
-	mov out0=in1
-	mov out1=in2
-	mov out2=in3
-	mov out3=in4
-	mov out5=in6
-	mov out6=in7
-	mov loc5=r19
-	mov loc6=r20
-	br.call.sptk.many rp=b6		// call the EFI function
-.ret1:	mov ar.rsc=0			// put RSE in enforced lazy, LE mode
-	mov r16=loc3
-	mov r19=loc5
-	mov r20=loc6
-	br.call.sptk.many rp=ia64_switch_mode_virt // return to virtual mode
-.ret2:	mov ar.rsc=loc4			// restore RSE configuration
-	mov ar.pfs=loc1
-	mov rp=loc0
-	mov gp=loc2
-	br.ret.sptk.many rp
-END(efi_call_phys)