Commit 717c0555 authored May 02, 2016 by David Hildenbrand Committed by Christian Borntraeger Jun 20, 2016

s390/mm: limit number of real-space gmap shadows



We have no known user of real-space designation and only support it to
be architecture compliant.

Gmap shadows with real-space designation are never unshadowed
automatically, as there is nothing to protect for the top level table.

So let's simply limit the number of such shadows to one by removing
existing ones on creation of another one.

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

parent 3218f709

arch/s390/mm/gmap.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -1455,6 +1455,19 @@ struct gmap gmap_shadow(struct gmap parent, unsigned long asce,
		gmap_free(new);
		return sg;
		}
		if (asce & _ASCE_REAL_SPACE) {
		/* only allow one real-space gmap shadow */
		list_for_each_entry(sg, &parent->children, list) {
		if (sg->orig_asce & _ASCE_REAL_SPACE) {
		spin_lock(&sg->guest_table_lock);
		gmap_unshadow(sg);
		spin_unlock(&sg->guest_table_lock);
		list_del(&sg->list);
		gmap_put(sg);
		break;
		}
		}
		}
		atomic_set(&new->ref_count, 2);
		list_add(&new->list, &parent->children);
		if (asce & _ASCE_REAL_SPACE) {

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