Re: [PATCH v3 01/25] KVM: Make support for kvm_arch_vcpu_async_ioctl() mandatory

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Thu, 16 Oct 2025 17:32:19 -0700
Sean Christopherson <seanjc@google.com> wrote:

> Implement kvm_arch_vcpu_async_ioctl() "natively" in x86 and arm64 instead
> of relying on an #ifdef'd stub, and drop HAVE_KVM_VCPU_ASYNC_IOCTL in
> anticipation of using the API on x86.  Once x86 uses the API, providing a
> stub for one architecture and having all other architectures opt-in
> requires more code than simply implementing the API in the lone holdout.
> 
> Eliminating the Kconfig will also reduce churn if the API is renamed in
> the future (spoiler alert).
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  arch/arm64/kvm/arm.c       |  6 ++++++
>  arch/loongarch/kvm/Kconfig |  1 -
>  arch/mips/kvm/Kconfig      |  1 -
>  arch/powerpc/kvm/Kconfig   |  1 -
>  arch/riscv/kvm/Kconfig     |  1 -
>  arch/s390/kvm/Kconfig      |  1 -
>  arch/x86/kvm/x86.c         |  6 ++++++
>  include/linux/kvm_host.h   | 10 ----------
>  virt/kvm/Kconfig           |  3 ---
>  9 files changed, 12 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index f21d1b7f20f8..785aaaee6a5d 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1828,6 +1828,12 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>  	return r;
>  }
>  
> +long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl,
> +			       unsigned long arg)
> +{
> +	return -ENOIOCTLCMD;
> +}
> +
>  void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
>  {
>  
> diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
> index ae64bbdf83a7..ed4f724db774 100644
> --- a/arch/loongarch/kvm/Kconfig
> +++ b/arch/loongarch/kvm/Kconfig
> @@ -25,7 +25,6 @@ config KVM
>  	select HAVE_KVM_IRQCHIP
>  	select HAVE_KVM_MSI
>  	select HAVE_KVM_READONLY_MEM
> -	select HAVE_KVM_VCPU_ASYNC_IOCTL
>  	select KVM_COMMON
>  	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
>  	select KVM_GENERIC_HARDWARE_ENABLING
> diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
> index ab57221fa4dd..cc13cc35f208 100644
> --- a/arch/mips/kvm/Kconfig
> +++ b/arch/mips/kvm/Kconfig
> @@ -22,7 +22,6 @@ config KVM
>  	select EXPORT_UASM
>  	select KVM_COMMON
>  	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> -	select HAVE_KVM_VCPU_ASYNC_IOCTL
>  	select KVM_MMIO
>  	select KVM_GENERIC_MMU_NOTIFIER
>  	select KVM_GENERIC_HARDWARE_ENABLING
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index 2f2702c867f7..c9a2d50ff1b0 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -20,7 +20,6 @@ if VIRTUALIZATION
>  config KVM
>  	bool
>  	select KVM_COMMON
> -	select HAVE_KVM_VCPU_ASYNC_IOCTL
>  	select KVM_VFIO
>  	select HAVE_KVM_IRQ_BYPASS
>  
> diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
> index c50328212917..77379f77840a 100644
> --- a/arch/riscv/kvm/Kconfig
> +++ b/arch/riscv/kvm/Kconfig
> @@ -23,7 +23,6 @@ config KVM
>  	select HAVE_KVM_IRQCHIP
>  	select HAVE_KVM_IRQ_ROUTING
>  	select HAVE_KVM_MSI
> -	select HAVE_KVM_VCPU_ASYNC_IOCTL
>  	select HAVE_KVM_READONLY_MEM
>  	select HAVE_KVM_DIRTY_RING_ACQ_REL
>  	select KVM_COMMON
> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> index cae908d64550..96d16028e8b7 100644
> --- a/arch/s390/kvm/Kconfig
> +++ b/arch/s390/kvm/Kconfig
> @@ -20,7 +20,6 @@ config KVM
>  	def_tristate y
>  	prompt "Kernel-based Virtual Machine (KVM) support"
>  	select HAVE_KVM_CPU_RELAX_INTERCEPT
> -	select HAVE_KVM_VCPU_ASYNC_IOCTL
>  	select KVM_ASYNC_PF
>  	select KVM_ASYNC_PF_SYNC
>  	select KVM_COMMON
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b4b5d2d09634..ca5ba2caf314 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7240,6 +7240,12 @@ static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp)
>  	return 0;
>  }
>  
> +long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl,
> +			       unsigned long arg)
> +{
> +	return -ENOIOCTLCMD;
> +}
> +
>  int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
>  {
>  	struct kvm *kvm = filp->private_data;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 5bd76cf394fa..7186b2ae4b57 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2437,18 +2437,8 @@ static inline bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
>  }
>  #endif /* CONFIG_HAVE_KVM_NO_POLL */
>  
> -#ifdef CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL
>  long kvm_arch_vcpu_async_ioctl(struct file *filp,
>  			       unsigned int ioctl, unsigned long arg);
> -#else
> -static inline long kvm_arch_vcpu_async_ioctl(struct file *filp,
> -					     unsigned int ioctl,
> -					     unsigned long arg)
> -{
> -	return -ENOIOCTLCMD;
> -}
> -#endif /* CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL */
> -
>  void kvm_arch_guest_memory_reclaimed(struct kvm *kvm);
>  
>  #ifdef CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index 5f0015c5dd95..267c7369c765 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -78,9 +78,6 @@ config HAVE_KVM_IRQ_BYPASS
>         tristate
>         select IRQ_BYPASS_MANAGER
>  
> -config HAVE_KVM_VCPU_ASYNC_IOCTL
> -       bool
> -
>  config HAVE_KVM_VCPU_RUN_PID_CHANGE
>         bool
>  


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