KVM: s390: reset KVM_REQ_MMU_RELOAD if mapping the prefix failed

When triggering KVM_RUN without a user memory region being mapped
(KVM_SET_USER_MEMORY_REGION) a validity intercept occurs. This could
happen, if the user memory region was not mapped initially or if it
was unmapped after the vcpu is initialized. The function
kvm_s390_handle_requests checks for the KVM_REQ_MMU_RELOAD bit. The
check function always clears this bit. If gmap_mprotect_notify
returns an error code, the mapping failed, but the KVM_REQ_MMU_RELOAD
was not set anymore. So the next time kvm_s390_handle_requests is
called, the execution would fall trough the check for
KVM_REQ_MMU_RELOAD. The bit needs to be resetted, if
gmap_mprotect_notify returns an error code. Resetting the bit with
kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu) fixes the bug.

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Julius Niedworok <jniedwor@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/kvm-s390.c

@@ -2362,8 +2362,10 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
 		rc = gmap_mprotect_notify(vcpu->arch.gmap,
 					  kvm_s390_get_prefix(vcpu),
 					  PAGE_SIZE * 2, PROT_WRITE);
-		if (rc)
+		if (rc) {
+			kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
 			return rc;
+		}
 		goto retry;
 	}