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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>
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1 changed files with 13 additions and 0 deletions
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@ -1455,6 +1455,19 @@ struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce,
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gmap_free(new);
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return sg;
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}
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if (asce & _ASCE_REAL_SPACE) {
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/* only allow one real-space gmap shadow */
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list_for_each_entry(sg, &parent->children, list) {
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if (sg->orig_asce & _ASCE_REAL_SPACE) {
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spin_lock(&sg->guest_table_lock);
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gmap_unshadow(sg);
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spin_unlock(&sg->guest_table_lock);
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list_del(&sg->list);
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gmap_put(sg);
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break;
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}
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}
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}
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atomic_set(&new->ref_count, 2);
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list_add(&new->list, &parent->children);
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if (asce & _ASCE_REAL_SPACE) {
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