s390/kvm: Add documentation for KVM_S390_INTERRUPT

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Documentation/virtual/kvm/api.txt

@@ -1997,6 +1997,39 @@ return the hash table order in the parameter.  (If the guest is using
 the virtualized real-mode area (VRMA) facility, the kernel will
 re-create the VMRA HPTEs on the next KVM_RUN of any vcpu.)
 
+4.77 KVM_S390_INTERRUPT
+
+Capability: basic
+Architectures: s390
+Type: vm ioctl, vcpu ioctl
+Parameters: struct kvm_s390_interrupt (in)
+Returns: 0 on success, -1 on error
+
+Allows to inject an interrupt to the guest. Interrupts can be floating
+(vm ioctl) or per cpu (vcpu ioctl), depending on the interrupt type.
+
+Interrupt parameters are passed via kvm_s390_interrupt:
+
+struct kvm_s390_interrupt {
+	__u32 type;
+	__u32 parm;
+	__u64 parm64;
+};
+
+type can be one of the following:
+
+KVM_S390_SIGP_STOP (vcpu) - sigp restart
+KVM_S390_PROGRAM_INT (vcpu) - program check; code in parm
+KVM_S390_SIGP_SET_PREFIX (vcpu) - sigp set prefix; prefix address in parm
+KVM_S390_RESTART (vcpu) - restart
+KVM_S390_INT_VIRTIO (vm) - virtio external interrupt; external interrupt
+			   parameters in parm and parm64
+KVM_S390_INT_SERVICE (vm) - sclp external interrupt; sclp parameter in parm
+KVM_S390_INT_EMERGENCY (vcpu) - sigp emergency; source cpu in parm
+KVM_S390_INT_EXTERNAL_CALL (vcpu) - sigp external call; source cpu in parm
+
+Note that the vcpu ioctl is asynchronous to vcpu execution.
+
 
 5. The kvm_run structure
 ------------------------