Re: [PATCH v16 02/22] KVM: x86: Have all vendor neutral sub-configs depend on KVM_X86, not just KVM

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 7/23/2025 6:46 PM, Fuad Tabba wrote:
> From: Sean Christopherson <seanjc@google.com>
> 
> Make all vendor neutral KVM x86 configs depend on KVM_X86, not just KVM,
> i.e. gate them on at least one vendor module being enabled and thus on
> kvm.ko actually being built.  Depending on just KVM allows the user to
> select the configs even though they won't actually take effect, and more
> importantly, makes it all too easy to create unmet dependencies.  E.g.
> KVM_GENERIC_PRIVATE_MEM can't be selected by KVM_SW_PROTECTED_VM, because
> the KVM_GENERIC_MMU_NOTIFIER dependency is select by KVM_X86.
> 
> Hiding all sub-configs when neither KVM_AMD nor KVM_INTEL is selected also
> helps communicate to the user that nothing "interesting" is going on, e.g.
> 
>    --- Virtualization
>    <M>   Kernel-based Virtual Machine (KVM) support
>    < >   KVM for Intel (and compatible) processors support
>    < >   KVM for AMD processors support

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

> Fixes: ea4290d77bda ("KVM: x86: leave kvm.ko out of the build if no vendor module is requested")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
>   arch/x86/kvm/Kconfig | 16 ++++++++--------
>   1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index 2c86673155c9..9895fc3cd901 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -74,7 +74,7 @@ config KVM_WERROR
>   	# FRAME_WARN, i.e. KVM_WERROR=y with KASAN=y requires special tuning.
>   	# Building KVM with -Werror and KASAN is still doable via enabling
>   	# the kernel-wide WERROR=y.
> -	depends on KVM && ((EXPERT && !KASAN) || WERROR)
> +	depends on KVM_X86 && ((EXPERT && !KASAN) || WERROR)
>   	help
>   	  Add -Werror to the build flags for KVM.
>   
> @@ -83,7 +83,7 @@ config KVM_WERROR
>   config KVM_SW_PROTECTED_VM
>   	bool "Enable support for KVM software-protected VMs"
>   	depends on EXPERT
> -	depends on KVM && X86_64
> +	depends on KVM_X86 && X86_64
>   	help
>   	  Enable support for KVM software-protected VMs.  Currently, software-
>   	  protected VMs are purely a development and testing vehicle for
> @@ -169,7 +169,7 @@ config KVM_AMD_SEV
>   config KVM_IOAPIC
>   	bool "I/O APIC, PIC, and PIT emulation"
>   	default y
> -	depends on KVM
> +	depends on KVM_X86
>   	help
>   	  Provides support for KVM to emulate an I/O APIC, PIC, and PIT, i.e.
>   	  for full in-kernel APIC emulation.
> @@ -179,7 +179,7 @@ config KVM_IOAPIC
>   config KVM_SMM
>   	bool "System Management Mode emulation"
>   	default y
> -	depends on KVM
> +	depends on KVM_X86
>   	help
>   	  Provides support for KVM to emulate System Management Mode (SMM)
>   	  in virtual machines.  This can be used by the virtual machine
> @@ -189,7 +189,7 @@ config KVM_SMM
>   
>   config KVM_HYPERV
>   	bool "Support for Microsoft Hyper-V emulation"
> -	depends on KVM
> +	depends on KVM_X86
>   	default y
>   	help
>   	  Provides KVM support for emulating Microsoft Hyper-V.  This allows KVM
> @@ -203,7 +203,7 @@ config KVM_HYPERV
>   
>   config KVM_XEN
>   	bool "Support for Xen hypercall interface"
> -	depends on KVM
> +	depends on KVM_X86
>   	help
>   	  Provides KVM support for the hosting Xen HVM guests and
>   	  passing Xen hypercalls to userspace.
> @@ -213,7 +213,7 @@ config KVM_XEN
>   config KVM_PROVE_MMU
>   	bool "Prove KVM MMU correctness"
>   	depends on DEBUG_KERNEL
> -	depends on KVM
> +	depends on KVM_X86
>   	depends on EXPERT
>   	help
>   	  Enables runtime assertions in KVM's MMU that are too costly to enable
> @@ -228,7 +228,7 @@ config KVM_EXTERNAL_WRITE_TRACKING
>   
>   config KVM_MAX_NR_VCPUS
>   	int "Maximum number of vCPUs per KVM guest"
> -	depends on KVM
> +	depends on KVM_X86
>   	range 1024 4096
>   	default 4096 if MAXSMP
>   	default 1024