s390/uv: Convert uv_destroy_owned_page() to uv_destroy_(folio|pte)()

Let's have the following variants for destroying pages:

(1) uv_destroy(): Like uv_pin_shared() and uv_convert_from_secure(),
"low level" helper that operates on paddr and doesn't mess with folios.

(2) uv_destroy_folio(): Consumes a folio to which we hold a reference.

(3) uv_destroy_pte(): Consumes a PTE that holds a reference through the
mapping.

Unfortunately we need uv_destroy_pte(), because pfn_folio() and
friends are not available in pgtable.h.
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20240508182955.358628-8-david@redhat.comSigned-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/include/asm/pgtable.h

@@ -1217,7 +1217,7 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
 	 * The notifier should have destroyed all protected vCPUs at this
 	 * point, so the destroy should be successful.
 	 */
-	if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
+	if (full && !uv_destroy_pte(res))
 		return res;
 	/*
 	 * If something went wrong and the page could not be destroyed, or

arch/s390/include/asm/uv.h

@@ -483,7 +483,8 @@ static inline int is_prot_virt_host(void)
 int uv_pin_shared(unsigned long paddr);
 int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb);
 int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr);
-int uv_destroy_owned_page(unsigned long paddr);
+int uv_destroy_folio(struct folio *folio);
+int uv_destroy_pte(pte_t pte);
 int uv_convert_owned_from_secure(unsigned long paddr);
 int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr);
 
@@ -497,7 +498,12 @@ static inline int uv_pin_shared(unsigned long paddr)
 	return 0;
 }
 
-static inline int uv_destroy_owned_page(unsigned long paddr)
+static inline int uv_destroy_folio(struct folio *folio)
+{
+	return 0;
+}
+
+static inline int uv_destroy_pte(pte_t pte)
 {
 	return 0;
 }

arch/s390/kernel/uv.c

@@ -110,7 +110,7 @@ EXPORT_SYMBOL_GPL(uv_pin_shared);
  *
  * @paddr: Absolute host address of page to be destroyed
  */
-static int uv_destroy_page(unsigned long paddr)
+static int uv_destroy(unsigned long paddr)
 {
 	struct uv_cb_cfs uvcb = {
 		.header.cmd = UVC_CMD_DESTR_SEC_STOR,
@@ -131,11 +131,10 @@ static int uv_destroy_page(unsigned long paddr)
 }
 
 /*
- * The caller must already hold a reference to the page
+ * The caller must already hold a reference to the folio
  */
-int uv_destroy_owned_page(unsigned long paddr)
+int uv_destroy_folio(struct folio *folio)
 {
-	struct folio *folio = phys_to_folio(paddr);
 	int rc;
 
 	/* See gmap_make_secure(): large folios cannot be secure */
@@ -143,13 +142,22 @@ int uv_destroy_owned_page(unsigned long paddr)
 		return 0;
 
 	folio_get(folio);
-	rc = uv_destroy_page(paddr);
+	rc = uv_destroy(folio_to_phys(folio));
 	if (!rc)
 		clear_bit(PG_arch_1, &folio->flags);
 	folio_put(folio);
 	return rc;
 }
 
+/*
+ * The present PTE still indirectly holds a folio reference through the mapping.
+ */
+int uv_destroy_pte(pte_t pte)
+{
+	VM_WARN_ON(!pte_present(pte));
+	return uv_destroy_folio(pfn_folio(pte_pfn(pte)));
+}
+
 /*
  * Requests the Ultravisor to encrypt a guest page and make it
  * accessible to the host for paging (export).
@@ -437,6 +445,7 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
 {
 	struct vm_area_struct *vma;
 	unsigned long uaddr;
+	struct folio *folio;
 	struct page *page;
 	int rc;
 
@@ -460,7 +469,8 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
 	page = follow_page(vma, uaddr, FOLL_WRITE | FOLL_GET);
 	if (IS_ERR_OR_NULL(page))
 		goto out;
-	rc = uv_destroy_owned_page(page_to_phys(page));
+	folio = page_folio(page);
+	rc = uv_destroy_folio(folio);
 	/*
 	 * Fault handlers can race; it is possible that two CPUs will fault
 	 * on the same secure page. One CPU can destroy the page, reboot,
@@ -472,7 +482,7 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
 	 */
 	if (rc)
 		rc = uv_convert_owned_from_secure(page_to_phys(page));
-	put_page(page);
+	folio_put(folio);
 out:
 	mmap_read_unlock(gmap->mm);
 	return rc;

arch/s390/mm/gmap.c

@@ -2841,13 +2841,15 @@ static const struct mm_walk_ops gather_pages_ops = {
  */
 void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
 {
+	struct folio *folio;
 	unsigned long i;
 
 	for (i = 0; i < count; i++) {
+		folio = pfn_folio(pfns[i]);
 		/* we always have an extra reference */
-		uv_destroy_owned_page(pfn_to_phys(pfns[i]));
+		uv_destroy_folio(folio);
 		/* get rid of the extra reference */
-		put_page(pfn_to_page(pfns[i]));
+		folio_put(folio);
 		cond_resched();
 	}
 }