On Wed, Dec 04, 2024, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@xxxxxxxx> > > There are very few 32-bit machines that support KVM, the main exceptions > are the "Yonah" Generation Xeon-LV and Core Duo from 2006 and the Atom > Z5xx "Silverthorne" from 2008 that were all release just before their > 64-bit counterparts. > > Using KVM as a host on a 64-bit CPU using a 32-bit kernel generally > works fine, but is rather pointless since 64-bit kernels are much better > supported and deal better with the memory requirements of VM guests. > > Drop all the 32-bit-only portions and the "#ifdef CONFIG_X86_64" checks > of the x86 KVM code and add a Kconfig dependency to only allow building > this on 64-bit kernels. While 32-bit KVM doesn't need to be a thing for x86 usage, Paolo expressed concerns that dropping 32-bit support on x86 would cause general 32-bit KVM support to bitrot horribly. 32-bit x86 doesn't get much testing, but I do at least boot VMs with it on a semi-regular basis. I don't think we can say the same for other architectures with 32-bit variants. PPC apparently still has 32-bit users[1][2], and 32-bit RISC-V is a thing, so I think we're stuck with 32-bit x86 for the time being. :-( [1] https://lore.kernel.org/all/87zg4aveow.fsf@mail.lhotse [2] https://lore.kernel.org/all/fc43f9eb-a60f-5c4a-a694-83029234a9c4@xxxxxxxxxxx
