Re: [PATCH] arm64: Kconfig: Make CPU_BIG_ENDIAN depend on BROKEN

[Catalin Marinas <catalin.marinas@arm.com>]

On Mon, Sep 29, 2025 at 02:18:55AM +0200, J. Neuschäfer wrote:
> On Fri, Sep 19, 2025 at 07:40:25PM +0100, Will Deacon wrote:
> > Big-endian arm64 configurations are vanishingly rare, yet we still claim
> > to support them in Linux despite very limited testing or visible
> > interest. Supporting big-endian adds unnecessary burden to reviewers and
> > contributors which, without any known active users, is hard to justify.
> > For example, recent work to improve our futex routines and to implement
> > nested virtualisation support is non-trivially complicated by having to
> > support both big- and little-endianness.
> > 
> > Back in 2019 [1], it was claimed that Huawei were using arm64 big-endian
> > machines in their telecommunication products but I don't know whether
> > that's still the case and certainly haven't seen any patch contributions
> > to help support or maintain it.
> > 
> > Make CPU_BIG_ENDIAN depend on BROKEN as an initial deprecation step
> > towards its removal.
> 
> As of this month (September 2025) there's a new community project [1,2]
> to revive aarch64_be. Jens Reidel (CC'd) and I are involved in it. We've
> been fixing several aarch64_be-related bugs, but mostly[3] in userspace,
> because the kernel support is pretty solid.
> 
> So, just so it doesn't go unmentioned, there is interest in keeping
> big-endian ARM64 alive.

It's nice to see it gets testing but is there any actual beyond you and
Jens (i.e. in production somewhere like Huawei's case)? We want to
assess whether it's worth the kernel maintenance and testing hassle and
for how long.

-- 
Catalin