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

[Greg Kurz]

On Mon, 30 Sep 2019 14:01:56 +0200
Cédric Le Goater <clg at kaod.org> wrote:

> 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.
> 

Simpler code in the callers IMHO.

> 
> 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) {
> > 
>