KVM: s390: dont allocate dirty bitmap

This patch #ifdefs the bitmap array for dirty tracking. We don't have dirty
tracking on s390 today, and we'd love to use our storage keys to store the
dirty information for migration. Therefore, we won't need this array at all,
and due to our limited amount of vmalloc space this limits the amount of guests
we can run.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7d10dfa..9ccaf8f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -359,6 +359,7 @@
 	r = -ENOMEM;
 
 	/* Allocate if a slot is being created */
+#ifndef CONFIG_S390
 	if (npages && !new.rmap) {
 		new.rmap = vmalloc(npages * sizeof(struct page *));
 
@@ -399,6 +400,7 @@
 			goto out_free;
 		memset(new.dirty_bitmap, 0, dirty_bytes);
 	}
+#endif /* not defined CONFIG_S390 */
 
 	if (mem->slot >= kvm->nmemslots)
 		kvm->nmemslots = mem->slot + 1;