1 files changed, 152 insertions, 25 deletions

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index b8ae4a4aa2ba..62758cb5872f 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2697,41 +2697,168 @@ void s390_reset_cmma(struct mm_struct *mm)
 }
 EXPORT_SYMBOL_GPL(s390_reset_cmma);
 
+#define GATHER_GET_PAGES 32
+
+struct reset_walk_state {
+	unsigned long next;
+	unsigned long count;
+	unsigned long pfns[GATHER_GET_PAGES];
+};
+
+static int s390_gather_pages(pte_t *ptep, unsigned long addr,
+			     unsigned long next, struct mm_walk *walk)
+{
+	struct reset_walk_state *p = walk->private;
+	pte_t pte = READ_ONCE(*ptep);
+
+	if (pte_present(pte)) {
+		/* we have a reference from the mapping, take an extra one */
+		get_page(phys_to_page(pte_val(pte)));
+		p->pfns[p->count] = phys_to_pfn(pte_val(pte));
+		p->next = next;
+		p->count++;
+	}
+	return p->count >= GATHER_GET_PAGES;
+}
+
+static const struct mm_walk_ops gather_pages_ops = {
+	.pte_entry = s390_gather_pages,
+};
+
 /*
- * make inaccessible pages accessible again
+ * Call the Destroy secure page UVC on each page in the given array of PFNs.
+ * Each page needs to have an extra reference, which will be released here.
  */
-static int __s390_reset_acc(pte_t *ptep, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
+void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
 {
-	pte_t pte = READ_ONCE(*ptep);
+	unsigned long i;
 
-	/* There is a reference through the mapping */
-	if (pte_present(pte))
-		WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK));
+	for (i = 0; i < count; i++) {
+		/* we always have an extra reference */
+		uv_destroy_owned_page(pfn_to_phys(pfns[i]));
+		/* get rid of the extra reference */
+		put_page(pfn_to_page(pfns[i]));
+		cond_resched();
+	}
+}
+EXPORT_SYMBOL_GPL(s390_uv_destroy_pfns);
 
+/**
+ * __s390_uv_destroy_range - Call the destroy secure page UVC on each page
+ * in the given range of the given address space.
+ * @mm: the mm to operate on
+ * @start: the start of the range
+ * @end: the end of the range
+ * @interruptible: if not 0, stop when a fatal signal is received
+ *
+ * Walk the given range of the given address space and call the destroy
+ * secure page UVC on each page. Optionally exit early if a fatal signal is
+ * pending.
+ *
+ * Return: 0 on success, -EINTR if the function stopped before completing
+ */
+int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
+			    unsigned long end, bool interruptible)
+{
+	struct reset_walk_state state = { .next = start };
+	int r = 1;
+
+	while (r > 0) {
+		state.count = 0;
+		mmap_read_lock(mm);
+		r = walk_page_range(mm, state.next, end, &gather_pages_ops, &state);
+		mmap_read_unlock(mm);
+		cond_resched();
+		s390_uv_destroy_pfns(state.count, state.pfns);
+		if (interruptible && fatal_signal_pending(current))
+			return -EINTR;
+	}
 	return 0;
 }
+EXPORT_SYMBOL_GPL(__s390_uv_destroy_range);
 
-static const struct mm_walk_ops reset_acc_walk_ops = {
-	.pte_entry		= __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;
 
-#include <linux/sched/mm.h>
-void s390_reset_acc(struct mm_struct *mm)
+	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)
 {
-	if (!mm_is_protected(mm))
-		return;
+	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));
+
 	/*
-	 * we might be called during
-	 * reset:                             we walk the pages and clear
-	 * close of all kvm file descriptors: we walk the pages and clear
-	 * exit of process on fd closure:     vma already gone, do nothing
+	 * 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.
 	 */
-	if (!mmget_not_zero(mm))
-		return;
-	mmap_read_lock(mm);
-	walk_page_range(mm, 0, TASK_SIZE, &reset_acc_walk_ops, NULL);
-	mmap_read_unlock(mm);
-	mmput(mm);
+	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_reset_acc);
+EXPORT_SYMBOL_GPL(s390_replace_asce);