KVM: PPC: Book3S HV: Implement H_CONFER

The H_CONFER hypercall is used when a guest vcpu is spinning on a lock
held by another vcpu which has been preempted, and the spinning vcpu
wishes to give its timeslice to the lock holder.  We implement this
in the straightforward way using kvm_vcpu_yield_to().

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 56f57af7e738..a010aa4cd026 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -538,6 +538,15 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
                 }
                 break;
         case H_CONFER:
+                target = kvmppc_get_gpr(vcpu, 4);
+                if (target == -1)
+                        break;
+                tvcpu = kvmppc_find_vcpu(vcpu->kvm, target);
+                if (!tvcpu) {
+                        ret = H_PARAMETER;
+                        break;
+                }
+                kvm_vcpu_yield_to(tvcpu);
                 break;
         case H_REGISTER_VPA:
                 ret = do_h_register_vpa(vcpu, kvmppc_get_gpr(vcpu, 4),