KVM: s390: make cmma usage conditionally

When userspace reset the guest without notifying kvm, the CMMA state
of the pages might be unused, resulting in guest data corruption.
To avoid this, CMMA must be enabled only if userspace understands
the implications.

CMMA must be enabled before vCPU creation. It can't be switched off
once enabled.  All subsequently created vCPUs will be enabled for
CMMA according to the CMMA state of the VM.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[remove now unnecessary calls to page_table_reset_pgste]

arch/s390/kvm/kvm-s390.h

@@ -158,8 +158,11 @@ void s390_vcpu_block(struct kvm_vcpu *vcpu);
 void s390_vcpu_unblock(struct kvm_vcpu *vcpu);
 void exit_sie(struct kvm_vcpu *vcpu);
 void exit_sie_sync(struct kvm_vcpu *vcpu);
-/* are we going to support cmma? */
-bool kvm_enabled_cmma(void);
+int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu);
+void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu);
+/* is cmma enabled */
+bool kvm_s390_cmma_enabled(struct kvm *kvm);
+
 /* implemented in diag.c */
 int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);