Re: [PATCH v4 08/27] KVM: arm64: Prepare sharing arm64 code with s390

[Marc Zyngier <maz@kernel.org>]

On Mon, 06 Jul 2026 09:52:08 +0100,
Steffen Eiden <seiden@linux.ibm.com> wrote:
> 
> Mark functions that s390 can use to implement arm on s390 as shared
> functions.
> 
> No functional change.
> 
> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
> ---
>  arch/arm64/kvm/arm.c         |  3 +++
>  arch/arm64/kvm/guest.c       |  3 +++
>  arch/arm64/kvm/handle_exit.c |  6 ++++++
>  arch/arm64/kvm/mmio.c        | 14 ++++++++++++++
>  arch/arm64/kvm/reset.c       |  3 +++
>  5 files changed, 29 insertions(+)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 50adfff75be8..c992308b2dce 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1580,6 +1580,7 @@ static unsigned long system_supported_vcpu_features(void)
>  	return features;
>  }
>  
> +#ifdef ARM64_S390_COMMON
>  static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu,
>  					const struct kvm_vcpu_init *init)
>  {
> @@ -1628,6 +1629,8 @@ static bool kvm_vcpu_init_changed(struct kvm_vcpu *vcpu,
>  			     KVM_VCPU_MAX_FEATURES);
>  }
>  
> +#endif /* ARM64_S390_COMMON */
> +
>  static int kvm_setup_vcpu(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm *kvm = vcpu->kvm;
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index b01d6622b872..5a202cfd27bc 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -543,6 +543,7 @@ int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
>  	return -EINVAL;
>  }
>  
> +#ifdef ARM64_S390_COMMON
>  static int copy_core_reg_indices(const struct kvm_vcpu *vcpu,
>  				 u64 __user *uindices)
>  {
> @@ -591,6 +592,8 @@ static unsigned long num_core_regs(const struct kvm_vcpu *vcpu)
>  	return copy_core_reg_indices(vcpu, NULL);
>  }
>  
> +#endif /* ARM64_S390_COMMON */
> +
>  static unsigned long num_sve_regs(const struct kvm_vcpu *vcpu)
>  {
>  	const unsigned int slices = vcpu_sve_slices(vcpu);
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 54aedf93c78b..d511af145ee6 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -213,6 +213,7 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu)
>  	return 0;
>  }
>  
> +#ifdef ARM64_S390_COMMON
>  static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu)
>  {
>  	u64 esr = kvm_vcpu_get_esr(vcpu);
> @@ -224,6 +225,8 @@ static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu)
>  	return 1;
>  }
>  
> +#endif /* ARM64_S390_COMMON */
> +
>  /*
>   * Guest access to SVE registers should be routed to this handler only
>   * when the system doesn't support SVE.
> @@ -404,6 +407,7 @@ static exit_handle_fn arm_exit_handlers[] = {
>  	[ESR_ELx_EC_GCS]	= kvm_handle_gcs,
>  };
>  
> +#ifdef ARM64_S390_COMMON
>  static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
>  {
>  	u64 esr = kvm_vcpu_get_esr(vcpu);
> @@ -439,6 +443,8 @@ static int handle_trap_exceptions(struct kvm_vcpu *vcpu)
>  	return handled;
>  }
>  
> +#endif /* ARM64_S390_COMMON */
> +
>  /*
>   * Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
>   * proper exit to userspace.
> diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c
> index e2285ed8c91d..876d56dd5b64 100644
> --- a/arch/arm64/kvm/mmio.c
> +++ b/arch/arm64/kvm/mmio.c
> @@ -10,6 +10,7 @@
>  
>  #include "trace.h"
>  
> +#ifdef ARM64_S390_COMMON
>  void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data)
>  {
>  	void *datap = NULL;
> @@ -135,8 +136,11 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
>  		if (!kvm_vcpu_dabt_issf(vcpu))
>  			data = data & 0xffffffff;
>  
> +#endif /* ARM64_S390_COMMON */
>  		trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
>  			       &data);
> +		//TODO  tracing
> +#ifdef ARM64_S390_COMMON

Irk. The deal is that you lift full functions, not cherry-pick which
lines you want. Just define empty stubs for the trace nonsense, and be
done with it. But not this, please!

	M.

-- 
Jazz isn't dead. It just smells funny.