Re: [PATCH v3 02/25] KVM: Rename kvm_arch_vcpu_async_ioctl() to kvm_arch_vcpu_unlocked_ioctl()

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

On Thu, 16 Oct 2025 17:32:20 -0700
Sean Christopherson <seanjc@google.com> wrote:

> Rename the "async" ioctl API to "unlocked" so that upcoming usage in x86's
> TDX code doesn't result in a massive misnomer.  To avoid having to retry
> SEAMCALLs, TDX needs to acquire kvm->lock *and* all vcpu->mutex locks, and
> acquiring all of those locks after/inside the current vCPU's mutex is a
> non-starter.  However, TDX also needs to acquire the vCPU's mutex and load
> the vCPU, i.e. the handling is very much not async to the vCPU.
> 
> 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       | 4 ++--
>  arch/loongarch/kvm/vcpu.c  | 4 ++--
>  arch/mips/kvm/mips.c       | 4 ++--
>  arch/powerpc/kvm/powerpc.c | 4 ++--
>  arch/riscv/kvm/vcpu.c      | 4 ++--
>  arch/s390/kvm/kvm-s390.c   | 4 ++--
>  arch/x86/kvm/x86.c         | 4 ++--
>  include/linux/kvm_host.h   | 4 ++--
>  virt/kvm/kvm_main.c        | 6 +++---
>  9 files changed, 19 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 785aaaee6a5d..e8d654024608 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1828,8 +1828,8 @@ 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)
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
> +				  unsigned long arg)
>  {
>  	return -ENOIOCTLCMD;
>  }
> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> index 30e3b089a596..9a5844e85fd3 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -1471,8 +1471,8 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, struct kvm_interrupt *irq)
>  	return 0;
>  }
>  
> -long kvm_arch_vcpu_async_ioctl(struct file *filp,
> -			       unsigned int ioctl, unsigned long arg)
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
> +				  unsigned long arg)
>  {
>  	void __user *argp = (void __user *)arg;
>  	struct kvm_vcpu *vcpu = filp->private_data;
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index a75587018f44..b0fb92fda4d4 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -895,8 +895,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
>  	return r;
>  }
>  
> -long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl,
> -			       unsigned long arg)
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
> +				  unsigned long arg)
>  {
>  	struct kvm_vcpu *vcpu = filp->private_data;
>  	void __user *argp = (void __user *)arg;
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2ba057171ebe..9a89a6d98f97 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -2028,8 +2028,8 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
>  	return -EINVAL;
>  }
>  
> -long kvm_arch_vcpu_async_ioctl(struct file *filp,
> -			       unsigned int ioctl, unsigned long arg)
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
> +				  unsigned long arg)
>  {
>  	struct kvm_vcpu *vcpu = filp->private_data;
>  	void __user *argp = (void __user *)arg;
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index bccb919ca615..a4bd6077eecc 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -238,8 +238,8 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
>  	return VM_FAULT_SIGBUS;
>  }
>  
> -long kvm_arch_vcpu_async_ioctl(struct file *filp,
> -			       unsigned int ioctl, unsigned long arg)
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
> +				  unsigned long arg)
>  {
>  	struct kvm_vcpu *vcpu = filp->private_data;
>  	void __user *argp = (void __user *)arg;
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 16ba04062854..8c4caa5f2fcd 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -5730,8 +5730,8 @@ static long kvm_s390_vcpu_memsida_op(struct kvm_vcpu *vcpu,
>  	return r;
>  }
>  
> -long kvm_arch_vcpu_async_ioctl(struct file *filp,
> -			       unsigned int ioctl, unsigned long arg)
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
> +				  unsigned long arg)
>  {
>  	struct kvm_vcpu *vcpu = filp->private_data;
>  	void __user *argp = (void __user *)arg;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ca5ba2caf314..b85cb213a336 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7240,8 +7240,8 @@ 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)
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
> +				  unsigned long arg)
>  {
>  	return -ENOIOCTLCMD;
>  }
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 7186b2ae4b57..d93f75b05ae2 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1557,6 +1557,8 @@ long kvm_arch_dev_ioctl(struct file *filp,
>  			unsigned int ioctl, unsigned long arg);
>  long kvm_arch_vcpu_ioctl(struct file *filp,
>  			 unsigned int ioctl, unsigned long arg);
> +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp,
> +				  unsigned int ioctl, unsigned long arg);
>  vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf);
>  
>  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext);
> @@ -2437,8 +2439,6 @@ static inline bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
>  }
>  #endif /* CONFIG_HAVE_KVM_NO_POLL */
>  
> -long kvm_arch_vcpu_async_ioctl(struct file *filp,
> -			       unsigned int ioctl, unsigned long arg);
>  void kvm_arch_guest_memory_reclaimed(struct kvm *kvm);
>  
>  #ifdef CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b7a0ae2a7b20..b7db1d5f71a8 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4434,10 +4434,10 @@ static long kvm_vcpu_ioctl(struct file *filp,
>  		return r;
>  
>  	/*
> -	 * Some architectures have vcpu ioctls that are asynchronous to vcpu
> -	 * execution; mutex_lock() would break them.
> +	 * Let arch code handle select vCPU ioctls without holding vcpu->mutex,
> +	 * e.g. to support ioctls that can run asynchronous to vCPU execution.
>  	 */
> -	r = kvm_arch_vcpu_async_ioctl(filp, ioctl, arg);
> +	r = kvm_arch_vcpu_unlocked_ioctl(filp, ioctl, arg);
>  	if (r != -ENOIOCTLCMD)
>  		return r;
>