[PATCH v2 4/6] KVM: PPC: Book3S HV: XIVE: Compute the VP id in a common helper

[Cédric Le Goater]

On 27/09/2019 13:53, Greg Kurz wrote:
> Reduce code duplication by consolidating the checking of vCPU ids and VP
> ids to a common helper used by both legacy and native XIVE KVM devices.
> And explain the magic with a comment.
> 
> Signed-off-by: Greg Kurz <groug at kaod.org>

Looks fine. One question below,

> ---
>  arch/powerpc/kvm/book3s_xive.c        |   42 ++++++++++++++++++++++++++-------
>  arch/powerpc/kvm/book3s_xive.h        |    1 +
>  arch/powerpc/kvm/book3s_xive_native.c |   11 ++-------
>  3 files changed, 36 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> index 0b7859e40f66..d84da9f6ee88 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c
> @@ -1211,6 +1211,37 @@ void kvmppc_xive_cleanup_vcpu(struct kvm_vcpu *vcpu)
>  	vcpu->arch.xive_vcpu = NULL;
>  }
>  
> +static bool kvmppc_xive_vcpu_id_valid(struct kvmppc_xive *xive, u32 cpu)
> +{
> +	/* We have a block of KVM_MAX_VCPUS VPs. We just need to check
> +	 * raw vCPU ids are below the expected limit for this guest's
> +	 * core stride ; kvmppc_pack_vcpu_id() will pack them down to an
> +	 * index that can be safely used to compute a VP id that belongs
> +	 * to the VP block.
> +	 */
> +	return cpu < KVM_MAX_VCPUS * xive->kvm->arch.emul_smt_mode;
> +}
> +
> +int kvmppc_xive_compute_vp_id(struct kvmppc_xive *xive, u32 cpu, u32 *vp)
> +{
> +	u32 vp_id;
> +
> +	if (!kvmppc_xive_vcpu_id_valid(xive, cpu)) {
> +		pr_devel("Out of bounds !\n");
> +		return -EINVAL;
> +	}
> +
> +	vp_id = kvmppc_xive_vp(xive, cpu);
> +	if (kvmppc_xive_vp_in_use(xive->kvm, vp_id)) {
> +		pr_devel("Duplicate !\n");
> +		return -EEXIST;
> +	}
> +
> +	*vp = vp_id;
> +
> +	return 0;

why not return vp_id ? and test for a negative value in callers.


C.

> +}
> +
>  int kvmppc_xive_connect_vcpu(struct kvm_device *dev,
>  			     struct kvm_vcpu *vcpu, u32 cpu)
>  {
> @@ -1229,20 +1260,13 @@ int kvmppc_xive_connect_vcpu(struct kvm_device *dev,
>  		return -EPERM;
>  	if (vcpu->arch.irq_type != KVMPPC_IRQ_DEFAULT)
>  		return -EBUSY;
> -	if (cpu >= (KVM_MAX_VCPUS * vcpu->kvm->arch.emul_smt_mode)) {
> -		pr_devel("Out of bounds !\n");
> -		return -EINVAL;
> -	}
>  
>  	/* We need to synchronize with queue provisioning */
>  	mutex_lock(&xive->lock);
>  
> -	vp_id = kvmppc_xive_vp(xive, cpu);
> -	if (kvmppc_xive_vp_in_use(xive->kvm, vp_id)) {
> -		pr_devel("Duplicate !\n");
> -		r = -EEXIST;
> +	r = kvmppc_xive_compute_vp_id(xive, cpu, &vp_id);
> +	if (r)
>  		goto bail;
> -	}
>  
>  	xc = kzalloc(sizeof(*xc), GFP_KERNEL);
>  	if (!xc) {
> diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h
> index fe3ed50e0818..90cf6ec35a68 100644
> --- a/arch/powerpc/kvm/book3s_xive.h
> +++ b/arch/powerpc/kvm/book3s_xive.h
> @@ -296,6 +296,7 @@ int kvmppc_xive_attach_escalation(struct kvm_vcpu *vcpu, u8 prio,
>  struct kvmppc_xive *kvmppc_xive_get_device(struct kvm *kvm, u32 type);
>  void xive_cleanup_single_escalation(struct kvm_vcpu *vcpu,
>  				    struct kvmppc_xive_vcpu *xc, int irq);
> +int kvmppc_xive_compute_vp_id(struct kvmppc_xive *xive, u32 cpu, u32 *vp);
>  
>  #endif /* CONFIG_KVM_XICS */
>  #endif /* _KVM_PPC_BOOK3S_XICS_H */
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index 43a86858390a..5bb480b2aafd 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -118,19 +118,12 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev,
>  		return -EPERM;
>  	if (vcpu->arch.irq_type != KVMPPC_IRQ_DEFAULT)
>  		return -EBUSY;
> -	if (server_num >= (KVM_MAX_VCPUS * vcpu->kvm->arch.emul_smt_mode)) {
> -		pr_devel("Out of bounds !\n");
> -		return -EINVAL;
> -	}
>  
>  	mutex_lock(&xive->lock);
>  
> -	vp_id = kvmppc_xive_vp(xive, server_num);
> -	if (kvmppc_xive_vp_in_use(xive->kvm, vp_id)) {
> -		pr_devel("Duplicate !\n");
> -		rc = -EEXIST;
> +	rc = kvmppc_xive_compute_vp_id(xive, server_num, &vp_id);
> +	if (rc)
>  		goto bail;
> -	}
>  
>  	xc = kzalloc(sizeof(*xc), GFP_KERNEL);
>  	if (!xc) {
>