KVM: s390: implement KVM_(S|G)ET_MP_STATE for user space state control

This patch
- adds s390 specific MP states to linux headers and documents them
- implements the KVM_{SET,GET}_MP_STATE ioctls
- enables KVM_CAP_MP_STATE
- allows user space to control the VCPU state on s390.

If user space sets the VCPU state using the ioctl KVM_SET_MP_STATE, we can disable
manual changing of the VCPU state and trust user space to do the right thing.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

Documentation/virtual/kvm/api.txt

@@ -974,7 +974,7 @@ for vm-wide capabilities.
 4.38 KVM_GET_MP_STATE
 
 Capability: KVM_CAP_MP_STATE
-Architectures: x86, ia64
+Architectures: x86, ia64, s390
 Type: vcpu ioctl
 Parameters: struct kvm_mp_state (out)
 Returns: 0 on success; -1 on error
@@ -998,6 +998,12 @@ Possible values are:
                                  is waiting for an interrupt [x86, ia64]
  - KVM_MP_STATE_SIPI_RECEIVED:   the vcpu has just received a SIPI (vector
                                  accessible via KVM_GET_VCPU_EVENTS) [x86, ia64]
+ - KVM_MP_STATE_STOPPED:         the vcpu is stopped [s390]
+ - KVM_MP_STATE_CHECK_STOP:      the vcpu is in a special error state [s390]
+ - KVM_MP_STATE_OPERATING:       the vcpu is operating (running or halted)
+                                 [s390]
+ - KVM_MP_STATE_LOAD:            the vcpu is in a special load/startup state
+                                 [s390]
 
 On x86 and ia64, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
 in-kernel irqchip, the multiprocessing state must be maintained by userspace on
@@ -1007,7 +1013,7 @@ these architectures.
 4.39 KVM_SET_MP_STATE
 
 Capability: KVM_CAP_MP_STATE
-Architectures: x86, ia64
+Architectures: x86, ia64, s390
 Type: vcpu ioctl
 Parameters: struct kvm_mp_state (in)
 Returns: 0 on success; -1 on error