Linux 6.7 Set To Drop Support For Itanium IA-64

Since 2021 the Itanium IA-64 code was orphaned in the Linux kernel and over the course of this year there's been talk of retiring the Itanium code from the kernel, a.k.a. strip it out. It looks like 2023 will end with the Itanium IA-64 code indeed being removed from the Linux kernel.

Following those discussions over dropping IA-64 support from the kernel given its unmaintained state and no active users of IA-64 hardware on modern kernel versions, the plan is moving ahead with dropping the CPU architecture.

There was a pull request last week to go ahead and drop the IA-64 architecture. There is also a build fix so at least Linux 6.6, which is expected to be this year's Long Term Support (LTS) kernel release will at least have IA-64 support in good standing should anyone actually use it.

Removing the IA-64 support from the Linux kernel lightens the codebase by 65k lines of code. With the patch to remove the Itanium IA-64 architecture, Ard Biesheuvel notes:

"The Itanium architecture is obsolete, and an informal survey reveals that any residual use of Itanium hardware in production is mostly HP-UX or OpenVMS based.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.
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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 no longer has any IA-64 machines. GLIBC would like to get rid of IA-64 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, 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."

With last week's pull request the removal is now in asm-generic.git and pulled into today's linux-next state. Barring any surprises, the Itanium IA-64 removal will happen for Linux 6.7.

In the discussion of last week's pull, longtime kernel developer Thomas Gleixner commented, "Good riddance. Can we remove more of these crufty architectures please?"