[PATCH] xen: switch gnttab_end_foreign_access() to take a struct page pointer

[PATCH] xen: switch gnttab_end_foreign_access() to take a struct page pointer

[Juergen Gross]

Instead of a virtual kernel address use a pointer of the associated
struct page as second parameter of gnttab_end_foreign_access().

Most users have that pointer available already and are creating the
virtual address from it, risking problems in case the memory is
located in highmem.

gnttab_end_foreign_access() itself won't need to get the struct page
from the address again.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/block/xen-blkfront.c        | 6 +++---
 drivers/input/misc/xen-kbdfront.c   | 4 ++--
 drivers/net/xen-netfront.c          | 7 +++----
 drivers/xen/gntalloc.c              | 9 +++------
 drivers/xen/gntdev-dmabuf.c         | 2 +-
 drivers/xen/grant-table.c           | 8 ++++----
 drivers/xen/pvcalls-front.c         | 6 +++---
 drivers/xen/xen-front-pgdir-shbuf.c | 2 +-
 drivers/xen/xenbus/xenbus_client.c  | 2 +-
 include/xen/grant_table.h           | 6 +++---
 net/9p/trans_xen.c                  | 8 ++++----
 11 files changed, 28 insertions(+), 32 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 55e004d03ced..a88ce4426400 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1221,7 +1221,7 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo)
 			list_del(&persistent_gnt->node);
 			if (persistent_gnt->gref != INVALID_GRANT_REF) {
 				gnttab_end_foreign_access(persistent_gnt->gref,
-							  0UL);
+							  NULL);
 				rinfo->persistent_gnts_c--;
 			}
 			if (info->feature_persistent)
@@ -1244,7 +1244,7 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo)
 		       rinfo->shadow[i].req.u.rw.nr_segments;
 		for (j = 0; j < segs; j++) {
 			persistent_gnt = rinfo->shadow[i].grants_used[j];
-			gnttab_end_foreign_access(persistent_gnt->gref, 0UL);
+			gnttab_end_foreign_access(persistent_gnt->gref, NULL);
 			if (info->feature_persistent)
 				__free_page(persistent_gnt->page);
 			kfree(persistent_gnt);
@@ -1259,7 +1259,7 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo)
 
 		for (j = 0; j < INDIRECT_GREFS(segs); j++) {
 			persistent_gnt = rinfo->shadow[i].indirect_grants[j];
-			gnttab_end_foreign_access(persistent_gnt->gref, 0UL);
+			gnttab_end_foreign_access(persistent_gnt->gref, NULL);
 			__free_page(persistent_gnt->page);
 			kfree(persistent_gnt);
 		}
diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
index 1fc9b3e7007f..8d8ebdc2039b 100644
--- a/drivers/input/misc/xen-kbdfront.c
+++ b/drivers/input/misc/xen-kbdfront.c
@@ -481,7 +481,7 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
  error_evtchan:
 	xenbus_free_evtchn(dev, evtchn);
  error_grant:
-	gnttab_end_foreign_access(info->gref, 0UL);
+	gnttab_end_foreign_access(info->gref, NULL);
 	info->gref = -1;
 	return ret;
 }
@@ -492,7 +492,7 @@ static void xenkbd_disconnect_backend(struct xenkbd_info *info)
 		unbind_from_irqhandler(info->irq, info);
 	info->irq = -1;
 	if (info->gref >= 0)
-		gnttab_end_foreign_access(info->gref, 0UL);
+		gnttab_end_foreign_access(info->gref, NULL);
 	info->gref = -1;
 }
 
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 65ab907aca5a..8c0b9546d5a2 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1386,7 +1386,7 @@ static void xennet_release_tx_bufs(struct netfront_queue *queue)
 		queue->tx_skbs[i] = NULL;
 		get_page(queue->grant_tx_page[i]);
 		gnttab_end_foreign_access(queue->grant_tx_ref[i],
-					  (unsigned long)page_address(queue->grant_tx_page[i]));
+					  queue->grant_tx_page[i]);
 		queue->grant_tx_page[i] = NULL;
 		queue->grant_tx_ref[i] = INVALID_GRANT_REF;
 		add_id_to_list(&queue->tx_skb_freelist, queue->tx_link, i);
@@ -1418,8 +1418,7 @@ static void xennet_release_rx_bufs(struct netfront_queue *queue)
 		 * foreign access is ended (which may be deferred).
 		 */
 		get_page(page);
-		gnttab_end_foreign_access(ref,
-					  (unsigned long)page_address(page));
+		gnttab_end_foreign_access(ref, page);
 		queue->grant_rx_ref[id] = INVALID_GRANT_REF;
 
 		kfree_skb(skb);
@@ -1760,7 +1759,7 @@ static void xennet_end_access(int ref, void *page)
 {
 	/* This frees the page as a side-effect */
 	if (ref != INVALID_GRANT_REF)
-		gnttab_end_foreign_access(ref, (unsigned long)page);
+		gnttab_end_foreign_access(ref, virt_to_page(page));
 }
 
 static void xennet_disconnect_backend(struct netfront_info *info)
diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index 55acb32842a3..a15729beb9d1 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -175,8 +175,6 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
 
 static void __del_gref(struct gntalloc_gref *gref)
 {
-	unsigned long addr;
-
 	if (gref->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
 		uint8_t *tmp = kmap_local_page(gref->page);
 		tmp[gref->notify.pgoff] = 0;
@@ -190,10 +188,9 @@ static void __del_gref(struct gntalloc_gref *gref)
 	gref->notify.flags = 0;
 
 	if (gref->gref_id) {
-		if (gref->page) {
-			addr = (unsigned long)page_to_virt(gref->page);
-			gnttab_end_foreign_access(gref->gref_id, addr);
-		} else
+		if (gref->page)
+			gnttab_end_foreign_access(gref->gref_id, gref->page);
+		else
 			gnttab_free_grant_reference(gref->gref_id);
 	}
 
diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c
index 91073b4e4a20..940e5e9e8a54 100644
--- a/drivers/xen/gntdev-dmabuf.c
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -524,7 +524,7 @@ static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
 
 	for (i = 0; i < count; i++)
 		if (refs[i] != INVALID_GRANT_REF)
-			gnttab_end_foreign_access(refs[i], 0UL);
+			gnttab_end_foreign_access(refs[i], NULL);
 }
 
 static void dmabuf_imp_free_storage(struct gntdev_dmabuf *gntdev_dmabuf)
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 1a1aec0a88a1..1b9b28bc3228 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -430,13 +430,13 @@ int gnttab_try_end_foreign_access(grant_ref_t ref)
 }
 EXPORT_SYMBOL_GPL(gnttab_try_end_foreign_access);
 
-void gnttab_end_foreign_access(grant_ref_t ref, unsigned long page)
+void gnttab_end_foreign_access(grant_ref_t ref, struct page *page)
 {
 	if (gnttab_try_end_foreign_access(ref)) {
-		if (page != 0)
-			put_page(virt_to_page(page));
+		if (page)
+			put_page(page);
 	} else
-		gnttab_add_deferred(ref, page ? virt_to_page(page) : NULL);
+		gnttab_add_deferred(ref, page);
 }
 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
 
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index e254ed19488f..1826e8e67125 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -238,8 +238,8 @@ static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
 	spin_unlock(&bedata->socket_lock);
 
 	for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
-		gnttab_end_foreign_access(map->active.ring->ref[i], 0);
-	gnttab_end_foreign_access(map->active.ref, 0);
+		gnttab_end_foreign_access(map->active.ring->ref[i], NULL);
+	gnttab_end_foreign_access(map->active.ref, NULL);
 	free_page((unsigned long)map->active.ring);
 
 	kfree(map);
@@ -1117,7 +1117,7 @@ static int pvcalls_front_remove(struct xenbus_device *dev)
 		}
 	}
 	if (bedata->ref != -1)
-		gnttab_end_foreign_access(bedata->ref, 0);
+		gnttab_end_foreign_access(bedata->ref, NULL);
 	kfree(bedata->ring.sring);
 	kfree(bedata);
 	xenbus_switch_state(dev, XenbusStateClosed);
diff --git a/drivers/xen/xen-front-pgdir-shbuf.c b/drivers/xen/xen-front-pgdir-shbuf.c
index b6433761d42c..bef8d72a6ca6 100644
--- a/drivers/xen/xen-front-pgdir-shbuf.c
+++ b/drivers/xen/xen-front-pgdir-shbuf.c
@@ -135,7 +135,7 @@ void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf)
 
 		for (i = 0; i < buf->num_grefs; i++)
 			if (buf->grefs[i] != INVALID_GRANT_REF)
-				gnttab_end_foreign_access(buf->grefs[i], 0UL);
+				gnttab_end_foreign_access(buf->grefs[i], NULL);
 	}
 	kfree(buf->grefs);
 	kfree(buf->directory);
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index d6fdd2d209d3..d5f3f763717e 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -439,7 +439,7 @@ void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages,
 
 	for (i = 0; i < nr_pages; i++) {
 		if (grefs[i] != INVALID_GRANT_REF) {
-			gnttab_end_foreign_access(grefs[i], 0);
+			gnttab_end_foreign_access(grefs[i], NULL);
 			grefs[i] = INVALID_GRANT_REF;
 		}
 	}
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 7d0f2f0037b8..527c9907f99c 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -101,10 +101,10 @@ int gnttab_end_foreign_access_ref(grant_ref_t ref);
  * Eventually end access through the given grant reference, and once that
  * access has been ended, free the given page too.  Access will be ended
  * immediately iff the grant entry is not in use, otherwise it will happen
- * some time later.  page may be 0, in which case no freeing will occur.
+ * some time later.  page may be NULL, in which case no freeing will occur.
  * Note that the granted page might still be accessed (read or write) by the
  * other side after gnttab_end_foreign_access() returns, so even if page was
- * specified as 0 it is not allowed to just reuse the page for other
+ * specified as NULL it is not allowed to just reuse the page for other
  * purposes immediately. gnttab_end_foreign_access() will take an additional
  * reference to the granted page in this case, which is dropped only after
  * the grant is no longer in use.
@@ -112,7 +112,7 @@ int gnttab_end_foreign_access_ref(grant_ref_t ref);
  * gnttab_end_foreign_access() are done via alloc_pages_exact() (and freeing
  * via free_pages_exact()) in order to avoid high order pages.
  */
-void gnttab_end_foreign_access(grant_ref_t ref, unsigned long page);
+void gnttab_end_foreign_access(grant_ref_t ref, struct page *page);
 
 /*
  * End access through the given grant reference, iff the grant entry is
diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 77883b6788cd..833cd3792c51 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -279,13 +279,13 @@ static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 				grant_ref_t ref;
 
 				ref = priv->rings[i].intf->ref[j];
-				gnttab_end_foreign_access(ref, 0);
+				gnttab_end_foreign_access(ref, NULL);
 			}
 			free_pages_exact(priv->rings[i].data.in,
 				   1UL << (priv->rings[i].intf->ring_order +
 					   XEN_PAGE_SHIFT));
 		}
-		gnttab_end_foreign_access(priv->rings[i].ref, 0);
+		gnttab_end_foreign_access(priv->rings[i].ref, NULL);
 		free_page((unsigned long)priv->rings[i].intf);
 	}
 	kfree(priv->rings);
@@ -353,10 +353,10 @@ static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
 out:
 	if (bytes) {
 		for (i--; i >= 0; i--)
-			gnttab_end_foreign_access(ring->intf->ref[i], 0);
+			gnttab_end_foreign_access(ring->intf->ref[i], NULL);
 		free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
 	}
-	gnttab_end_foreign_access(ring->ref, 0);
+	gnttab_end_foreign_access(ring->ref, NULL);
 	free_page((unsigned long)ring->intf);
 	return ret;
 }
-- 
2.35.3

Re: [PATCH] xen: switch gnttab_end_foreign_access() to take a struct page pointer

[Jan Beulich]

On 24.05.2022 14:41, Juergen Gross wrote:
> Instead of a virtual kernel address use a pointer of the associated
> struct page as second parameter of gnttab_end_foreign_access().
> 
> Most users have that pointer available already and are creating the
> virtual address from it, risking problems in case the memory is
> located in highmem.
> 
> gnttab_end_foreign_access() itself won't need to get the struct page
> from the address again.
> 
> Suggested-by: Jan Beulich <jbeulich@suse.com>
> Signed-off-by: Juergen Gross <jgross@suse.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>