[PATCH v8 08/29] KVM: Move architecture capability Kconfigs to header defines

[Steffen Eiden]

On Fri, Sep 18, 2026 at 03:30:45PM +0200, Steffen Eiden wrote:
> Historically, KVM feature opt-ins and callbacks (e.g. read-only memory,
> MSI routing, generic pre-fault memory, lockless aging, halt-polling
> controls, and vcpu run PID changes) were configured globally via Kconfig
> symbols (CONFIG_HAVE_KVM_* and CONFIG_KVM_*).
> 
> With s390 hosting multiple independent KVM implementations within the
> same kernel build (native s390 KVM and arm64 on s390), global Kconfig
> selections force both implementations to inherit options that only apply
> to one of them. For instance, selecting KVM_GENERIC_PRE_FAULT_MEMORY for
> native s390 would force arm64 on s390 to provide unused dummy stubs.
> 
> Replace these global Kconfig options with architecture-specific opt-in
> defines in <asm/kvm_host.h> and standardize their naming by dropping the
> HAVE_ prefix:
>   - KVM_GENERIC_PRE_FAULT_MEMORY
>   - KVM_INVALID_WAKEUPS
>   - KVM_MSI               (formerly HAVE_KVM_MSI)
>   - KVM_NO_POLL           (formerly HAVE_KVM_NO_POLL)
>   - KVM_READONLY_MEM      (formerly HAVE_KVM_READONLY_MEM)
>   - KVM_VCPU_RUN_PID_CHANGE (formerly HAVE_KVM_VCPU_RUN_PID_CHANGE)
> 
> This allows each architecture and guest implementation to configure its
> supported capabilities independently in its kvm_host header and eliminates
> unnecessary fallback stubs across different KVM targets.
> 
> Signed-off-by: Steffen Eiden <seiden at linux.ibm.com>
> ---
>  arch/arm64/include/asm/kvm_host.h     |  3 +++
>  arch/arm64/kvm/Kconfig                |  3 ---
>  arch/loongarch/include/asm/kvm_host.h |  2 ++
>  arch/loongarch/kvm/Kconfig            |  2 --
>  arch/mips/include/asm/kvm_host.h      |  1 +
>  arch/mips/kvm/Kconfig                 |  1 -
>  arch/powerpc/include/asm/kvm_host.h   |  3 +++
>  arch/powerpc/kvm/Kconfig              |  1 -
>  arch/riscv/include/asm/kvm_host.h     |  2 ++
>  arch/riscv/kvm/Kconfig                |  2 --
>  arch/s390/include/asm/kvm_host_s390.h |  4 ++++
>  arch/s390/kvm/Kconfig                 |  3 ---
>  arch/x86/include/asm/kvm_host.h       |  4 ++++
>  arch/x86/kvm/Kconfig                  |  4 ----
>  include/linux/kvm_host.h              | 20 ++++++++++++--------
>  virt/kvm/Kconfig                      | 20 +-------------------
>  virt/kvm/kvm_main.c                   |  8 ++++----
>  17 files changed, 36 insertions(+), 47 deletions(-)
> 

...

> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index c3c0ee253fc7..008b110ebdb7 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -9,7 +9,7 @@ config KVM_COMMON
>         select PREEMPT_NOTIFIERS
>  
>  config HAVE_KVM_PFNCACHE
> -       bool
> +       booCONFIG_ltt

Sorry, that must have sneaked in last minute.
Obviously, this is a mistake.