@@ -148,4 +148,6 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long dirty_bitmap[4],
unsigned long gaddr, unsigned long vmaddr);
int gmap_mark_unmergeable(void);
void s390_reset_acc(struct mm_struct *mm);
+void s390_unlist_old_asce(struct gmap *gmap);
+int s390_replace_asce(struct gmap *gmap);
#endif /* _ASM_S390_GMAP_H */
@@ -161,10 +161,13 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
atomic_set(&kvm->mm->context.is_protected, 0);
KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
- /* Inteded memory leak on "impossible" error */
- if (!cc)
+ /* Intended memory leak on "impossible" error */
+ if (!cc) {
kvm_s390_pv_dealloc_vm(kvm);
- return cc ? -EIO : 0;
+ return 0;
+ }
+ s390_replace_asce(kvm->arch.gmap);
+ return -EIO;
}
int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
@@ -2721,3 +2721,89 @@ void s390_reset_acc(struct mm_struct *mm)
mmput(mm);
}
EXPORT_SYMBOL_GPL(s390_reset_acc);
+
+/**
+ * s390_unlist_old_asce - Remove the topmost level of page tables from the
+ * list of page tables of the gmap.
+ * @gmap the gmap whose table is to be removed
+ *
+ * On s390x, KVM keeps a list of all pages containing the page tables of the
+ * gmap (the CRST list). This list is used at tear down time to free all
+ * pages that are now not needed anymore.
+ *
+ * This function removes the topmost page of the tree (the one pointed to by
+ * the ASCE) from the CRST list.
+ *
+ * This means that it will not be freed when the VM is torn down, and needs
+ * to be handled separately by the caller, unless a leak is actually
+ * intended. Notice that this function will only remove the page from the
+ * list, the page will still be used as a top level page table (and ASCE).
+ */
+void s390_unlist_old_asce(struct gmap *gmap)
+{
+ struct page *old;
+
+ old = virt_to_page(gmap->table);
+ spin_lock(&gmap->guest_table_lock);
+ list_del(&old->lru);
+ /*
+ * Sometimes the topmost page might need to be "removed" multiple
+ * times, for example if the VM is rebooted into secure mode several
+ * times concurrently, or if s390_replace_asce fails after calling
+ * s390_remove_old_asce and is attempted again later. In that case
+ * the old asce has been removed from the list, and therefore it
+ * will not be freed when the VM terminates, but the ASCE is still
+ * in use and still pointed to.
+ * A subsequent call to replace_asce will follow the pointer and try
+ * to remove the same page from the list again.
+ * Therefore it's necessary that the page of the ASCE has valid
+ * pointers, so list_del can work (and do nothing) without
+ * dereferencing stale or invalid pointers.
+ */
+ INIT_LIST_HEAD(&old->lru);
+ spin_unlock(&gmap->guest_table_lock);
+}
+EXPORT_SYMBOL_GPL(s390_unlist_old_asce);
+
+/**
+ * s390_replace_asce - Try to replace the current ASCE of a gmap with a copy
+ * @gmap the gmap whose ASCE needs to be replaced
+ *
+ * If the allocation of the new top level page table fails, the ASCE is not
+ * replaced.
+ * In any case, the old ASCE is always removed from the gmap CRST list.
+ * Therefore the caller has to make sure to save a pointer to it
+ * beforehand, unless a leak is actually intended.
+ */
+int s390_replace_asce(struct gmap *gmap)
+{
+ unsigned long asce;
+ struct page *page;
+ void *table;
+
+ s390_unlist_old_asce(gmap);
+
+ page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
+ if (!page)
+ return -ENOMEM;
+ table = page_to_virt(page);
+ memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));
+
+ /*
+ * The caller has to deal with the old ASCE, but here we make sure
+ * the new one is properly added to the CRST list, so that
+ * it will be freed when the VM is torn down.
+ */
+ spin_lock(&gmap->guest_table_lock);
+ list_add(&page->lru, &gmap->crst_list);
+ spin_unlock(&gmap->guest_table_lock);
+
+ /* Set new table origin while preserving existing ASCE control bits */
+ asce = (gmap->asce & ~_ASCE_ORIGIN) | __pa(table);
+ WRITE_ONCE(gmap->asce, asce);
+ WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
+ WRITE_ONCE(gmap->table, table);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(s390_replace_asce);