KVM: s390: Provide guest TOD Clock Get/Set Controls

Provide controls for setting/getting the guest TOD clock based on the VM
attribute interface.

Provide TOD and TOD_HIGH vm attributes on s390 for managing guest Time Of
Day clock value.

TOD_HIGH is presently always set to 0. In the future it will contain a high
order expansion of the tod clock value after it overflows the 64-bits of
the TOD.

Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index a2dcd0e..8e22aa0 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -528,6 +528,7 @@
 	struct mutex ipte_mutex;
 	spinlock_t start_stop_lock;
 	struct kvm_s390_crypto crypto;
+	u64 epoch;
 };
 
 #define KVM_HVA_ERR_BAD		(-1UL)