Earlier this month as part of patches for cleaning up x86 32-bit kernel code for x86_64 systems, there was a patch to drop support for 32-bit x86 KVM host support. That patch has now been split off into its own patch series with also now raising the prospects of ending 32-bit KVM host support across all CPU architectures rather than being just an x86-only change.
The code for cleaning up the x86 kernel on x86_64 hardware patches continue moving along while now split off on their own are patches for ending 32-bit KVM host support across all architectures. The 32-bit KVM guest support would remain with these patches being about just ending support for 32-bit virtualization hosts… After all, who in 2025+ is likely running a leading-edge upstream kernel in a 32-bit environment and doing any virtualization hosting in production.
Rather than just dropping the 32-bit KVM host support for x86, it also ends the support for PowerPC, MIPS, and RISC-V. 32-bit ARM already dropped its KVM host support a few years back.
Arnd Bergmann argues in the patch series [RFC 0/5] KVM: drop 32-bit host support on all architectures:
“I submitted a patch to remove KVM support for x86-32 hosts earlier this month, but there were still concerns that this might be useful for testing 32-bit host in general, as that remains supported on three other architectures. I have gone through those three now and prepared similar patches, as all of them seem to be equally obsolete.
Support for 32-bit KVM host on Arm hardware was dropped back in 2020 because of lack of users, despite Cortex-A7/A15/A17 based SoCs being much more widely deployed than the other virtualization capable 32-bit CPUs (Intel Core Duo/Silverthorne, PowerPC e300/e500/e600, MIPS P5600) combined.
It probably makes sense to drop all of these at the same time, provided there are no actual users remaining (not counting regression testing that developers might be doing). Please let me know if you are still using any of these machines, or think there needs to be deprecation phase first.”
So should you actually be using a Linux 32-bit system as a Kernel-based Virtual Machine (KVM) host, now it’s time to let it be known and arguing if it should remain within the mainline Linux kernel… Especially if using an existing Linux LTS release isn’t feasible, such as the recently christened Linux 6.12 LTS.
We’ll see what happens with these patches for perhaps ending 32-bit KVM host support for good in 2025.
