Re: [PATCH v7 03/23] KVM: Allow KVM implementations to switch off MMIO independent of Kconfig

[Sean Christopherson]

On Mon, Aug 31, 2026, Steffen Eiden wrote:
> Only defining KVM_MMIO is not flexible enough for multi-KVM systems
> where one KVM implements MMIO but others do not. Solve this by
> additionally testing for the non-existence of KVM_NO_MMIO before
> including MMIO code to KVM.

Ewwwww.  IIUC, s390 ends up with two KVM modules, i.e. there really are two different
KVMs being built.  Rather than have a KVM_MMIO and NO_KVM_MMIO, I vote very
strongly to drop CONFIG_KVM_MMIO entirely and replace it with __KVM_HAVE_ARCH_MMIO,
a la __KVM_HAVE_ARCH_VM_FREE and others.  Tracking two separate macros is going
to be annoying to maintain, and will definitely be confusing for non-s390 people.

It'll mean linking in an emtpy coalesced_mmio.o on s390 when building without arm64
support, but I'm guessing that won't be at all common for s390 builds.