Merge tag 'for-linus-6.8-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:

 - update some Xen PV interface related headers

 - fix some kernel-doc comments in the xenbus driver

 - fix the Xen gntdev driver to not access the struct page of pages
   imported from a DMA-buf

* tag 'for-linus-6.8-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/gntdev: Fix the abuse of underlying struct page in DMA-buf import
  xen/xenbus: client: fix kernel-doc comments
  xen: update PV-device interface headers

5 files changed, 62 insertions, 53 deletions

diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c
index 4440e626b797..42adc2c1e06b 100644
--- a/drivers/xen/gntdev-dmabuf.c
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/dma-buf.h>
+#include <linux/dma-direct.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
@@ -50,7 +51,7 @@ struct gntdev_dmabuf {
 
 	/* Number of pages this buffer has. */
 	int nr_pages;
-	/* Pages of this buffer. */
+	/* Pages of this buffer (only for dma-buf export). */
 	struct page **pages;
 };
 
@@ -484,7 +485,7 @@ out:
 /* DMA buffer import support. */
 
 static int
-dmabuf_imp_grant_foreign_access(struct page **pages, u32 *refs,
+dmabuf_imp_grant_foreign_access(unsigned long *gfns, u32 *refs,
 				int count, int domid)
 {
 	grant_ref_t priv_gref_head;
@@ -507,7 +508,7 @@ dmabuf_imp_grant_foreign_access(struct page **pages, u32 *refs,
 		}
 
 		gnttab_grant_foreign_access_ref(cur_ref, domid,
-						xen_page_to_gfn(pages[i]), 0);
+						gfns[i], 0);
 		refs[i] = cur_ref;
 	}
 
@@ -529,7 +530,6 @@ static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
 
 static void dmabuf_imp_free_storage(struct gntdev_dmabuf *gntdev_dmabuf)
 {
-	kfree(gntdev_dmabuf->pages);
 	kfree(gntdev_dmabuf->u.imp.refs);
 	kfree(gntdev_dmabuf);
 }
@@ -549,12 +549,6 @@ static struct gntdev_dmabuf *dmabuf_imp_alloc_storage(int count)
 	if (!gntdev_dmabuf->u.imp.refs)
 		goto fail;
 
-	gntdev_dmabuf->pages = kcalloc(count,
-				       sizeof(gntdev_dmabuf->pages[0]),
-				       GFP_KERNEL);
-	if (!gntdev_dmabuf->pages)
-		goto fail;
-
 	gntdev_dmabuf->nr_pages = count;
 
 	for (i = 0; i < count; i++)
@@ -576,7 +570,8 @@ dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
 	struct dma_buf *dma_buf;
 	struct dma_buf_attachment *attach;
 	struct sg_table *sgt;
-	struct sg_page_iter sg_iter;
+	struct sg_dma_page_iter sg_iter;
+	unsigned long *gfns;
 	int i;
 
 	dma_buf = dma_buf_get(fd);
@@ -624,26 +619,31 @@ dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
 
 	gntdev_dmabuf->u.imp.sgt = sgt;
 
-	/* Now convert sgt to array of pages and check for page validity. */
+	gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL);
+	if (!gfns) {
+		ret = ERR_PTR(-ENOMEM);
+		goto fail_unmap;
+	}
+
+	/*
+	 * Now convert sgt to array of gfns without accessing underlying pages.
+	 * It is not allowed to access the underlying struct page of an sg table
+	 * exported by DMA-buf, but since we deal with special Xen dma device here
+	 * (not a normal physical one) look at the dma addresses in the sg table
+	 * and then calculate gfns directly from them.
+	 */
 	i = 0;
-	for_each_sgtable_page(sgt, &sg_iter, 0) {
-		struct page *page = sg_page_iter_page(&sg_iter);
-		/*
-		 * Check if page is valid: this can happen if we are given
-		 * a page from VRAM or other resources which are not backed
-		 * by a struct page.
-		 */
-		if (!pfn_valid(page_to_pfn(page))) {
-			ret = ERR_PTR(-EINVAL);
-			goto fail_unmap;
-		}
+	for_each_sgtable_dma_page(sgt, &sg_iter, 0) {
+		dma_addr_t addr = sg_page_iter_dma_address(&sg_iter);
+		unsigned long pfn = bfn_to_pfn(XEN_PFN_DOWN(dma_to_phys(dev, addr)));
 
-		gntdev_dmabuf->pages[i++] = page;
+		gfns[i++] = pfn_to_gfn(pfn);
 	}
 
-	ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gntdev_dmabuf->pages,
+	ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gfns,
 						      gntdev_dmabuf->u.imp.refs,
 						      count, domid));
+	kfree(gfns);
 	if (IS_ERR(ret))
 		goto fail_end_access;
 
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index d4b251925796..32835b4b9bc5 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -119,11 +119,13 @@ EXPORT_SYMBOL_GPL(xenbus_strstate);
  * @callback: callback to register
  *
  * Register a @watch on the given path, using the given xenbus_watch structure
- * for storage, and the given @callback function as the callback.  Return 0 on
- * success, or -errno on error.  On success, the given @path will be saved as
- * @watch->node, and remains the caller's to free.  On error, @watch->node will
+ * for storage, and the given @callback function as the callback.  On success,
+ * the given @path will be saved as @watch->node, and remains the
+ * caller's to free.  On error, @watch->node will
  * be NULL, the device will switch to %XenbusStateClosing, and the error will
  * be saved in the store.
+ *
+ * Returns: %0 on success or -errno on error
  */
 int xenbus_watch_path(struct xenbus_device *dev, const char *path,
 		      struct xenbus_watch *watch,
@@ -160,12 +162,14 @@ EXPORT_SYMBOL_GPL(xenbus_watch_path);
  * @pathfmt: format of path to watch
  *
  * Register a watch on the given @path, using the given xenbus_watch
- * structure for storage, and the given @callback function as the callback.
- * Return 0 on success, or -errno on error.  On success, the watched path
- * (@path/@path2) will be saved as @watch->node, and becomes the caller's to
- * kfree().  On error, watch->node will be NULL, so the caller has nothing to
+ * structure for storage, and the given @callback function as the
+ * callback.  On success, the watched path (@path/@path2) will be saved
+ * as @watch->node, and becomes the caller's to kfree().
+ * On error, watch->node will be NULL, so the caller has nothing to
  * free, the device will switch to %XenbusStateClosing, and the error will be
  * saved in the store.
+ *
+ * Returns: %0 on success or -errno on error
  */
 int xenbus_watch_pathfmt(struct xenbus_device *dev,
 			 struct xenbus_watch *watch,
@@ -255,13 +259,15 @@ abort:
 }
 
 /**
- * xenbus_switch_state
+ * xenbus_switch_state - save the new state of a driver
  * @dev: xenbus device
  * @state: new state
  *
  * Advertise in the store a change of the given driver to the given new_state.
- * Return 0 on success, or -errno on error.  On error, the device will switch
- * to XenbusStateClosing, and the error will be saved in the store.
+ * On error, the device will switch to XenbusStateClosing, and the error
+ * will be saved in the store.
+ *
+ * Returns: %0 on success or -errno on error
  */
 int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state)
 {
@@ -305,7 +311,7 @@ static void xenbus_va_dev_error(struct xenbus_device *dev, int err,
 }
 
 /**
- * xenbus_dev_error
+ * xenbus_dev_error - place an error message into the store
  * @dev: xenbus device
  * @err: error to report
  * @fmt: error message format
@@ -324,7 +330,7 @@ void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...)
 EXPORT_SYMBOL_GPL(xenbus_dev_error);
 
 /**
- * xenbus_dev_fatal
+ * xenbus_dev_fatal - put an error messages into the store and then shutdown
  * @dev: xenbus device
  * @err: error to report
  * @fmt: error message format
@@ -346,7 +352,7 @@ void xenbus_dev_fatal(struct xenbus_device *dev, int err, const char *fmt, ...)
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_fatal);
 
-/**
+/*
  * Equivalent to xenbus_dev_fatal(dev, err, fmt, args), but helps
  * avoiding recursion within xenbus_switch_state.
  */
@@ -453,7 +459,7 @@ void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages,
 }
 EXPORT_SYMBOL_GPL(xenbus_teardown_ring);
 
-/**
+/*
  * Allocate an event channel for the given xenbus_device, assigning the newly
  * created local port to *port.  Return 0 on success, or -errno on error.  On
  * error, the device will switch to XenbusStateClosing, and the error will be
@@ -479,7 +485,7 @@ int xenbus_alloc_evtchn(struct xenbus_device *dev, evtchn_port_t *port)
 EXPORT_SYMBOL_GPL(xenbus_alloc_evtchn);
 
 
-/**
+/*
  * Free an existing event channel. Returns 0 on success or -errno on error.
  */
 int xenbus_free_evtchn(struct xenbus_device *dev, evtchn_port_t port)
@@ -499,7 +505,7 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
 
 
 /**
- * xenbus_map_ring_valloc
+ * xenbus_map_ring_valloc - allocate & map pages of VA space
  * @dev: xenbus device
  * @gnt_refs: grant reference array
  * @nr_grefs: number of grant references
@@ -507,10 +513,11 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
  *
  * Map @nr_grefs pages of memory into this domain from another
  * domain's grant table.  xenbus_map_ring_valloc allocates @nr_grefs
- * pages of virtual address space, maps the pages to that address, and
- * sets *vaddr to that address.  Returns 0 on success, and -errno on
- * error. If an error is returned, device will switch to
+ * pages of virtual address space, maps the pages to that address, and sets
+ * *vaddr to that address.  If an error is returned, device will switch to
  * XenbusStateClosing and the error message will be saved in XenStore.
+ *
+ * Returns: %0 on success or -errno on error
  */
 int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
 			   unsigned int nr_grefs, void **vaddr)
@@ -599,14 +606,15 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
 }
 
 /**
- * xenbus_unmap_ring
+ * xenbus_unmap_ring - unmap memory from another domain
  * @dev: xenbus device
  * @handles: grant handle array
  * @nr_handles: number of handles in the array
  * @vaddrs: addresses to unmap
  *
  * Unmap memory in this domain that was imported from another domain.
- * Returns 0 on success and returns GNTST_* on error
+ *
+ * Returns: %0 on success or GNTST_* on error
  * (see xen/include/interface/grant_table.h).
  */
 static int xenbus_unmap_ring(struct xenbus_device *dev, grant_handle_t *handles,
@@ -712,7 +720,7 @@ static int xenbus_map_ring_hvm(struct xenbus_device *dev,
 }
 
 /**
- * xenbus_unmap_ring_vfree
+ * xenbus_unmap_ring_vfree - unmap a page of memory from another domain
  * @dev: xenbus device
  * @vaddr: addr to unmap
  *
@@ -720,7 +728,8 @@ static int xenbus_map_ring_hvm(struct xenbus_device *dev,
  * Unmap a page of memory in this domain that was imported from another domain.
  * Use xenbus_unmap_ring_vfree if you mapped in your memory with
  * xenbus_map_ring_valloc (it will free the virtual address space).
- * Returns 0 on success and returns GNTST_* on error
+ *
+ * Returns: %0 on success or GNTST_* on error
  * (see xen/include/interface/grant_table.h).
  */
 int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
@@ -916,10 +925,10 @@ static int xenbus_unmap_ring_hvm(struct xenbus_device *dev, void *vaddr)
 }
 
 /**
- * xenbus_read_driver_state
+ * xenbus_read_driver_state - read state from a store path
  * @path: path for driver
  *
- * Return the state of the driver rooted at the given store path, or
+ * Returns: the state of the driver rooted at the given store path, or
  * XenbusStateUnknown if no state can be read.
  */
 enum xenbus_state xenbus_read_driver_state(const char *path)
diff --git a/include/xen/interface/io/displif.h b/include/xen/interface/io/displif.h
index 18417b017869..60e42d3b760e 100644
--- a/include/xen/interface/io/displif.h
+++ b/include/xen/interface/io/displif.h
@@ -537,7 +537,7 @@ struct xendispl_dbuf_create_req {
 
 struct xendispl_page_directory {
 	grant_ref_t gref_dir_next_page;
-	grant_ref_t gref[1]; /* Variable length */
+	grant_ref_t gref[];
 };
 
 /*
diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h
index ba4c4274b714..4fef1efcdcab 100644
--- a/include/xen/interface/io/ring.h
+++ b/include/xen/interface/io/ring.h
@@ -95,7 +95,7 @@ struct __name##_sring {                                                 \
     RING_IDX req_prod, req_event;                                       \
     RING_IDX rsp_prod, rsp_event;                                       \
     uint8_t __pad[48];                                                  \
-    union __name##_sring_entry ring[1]; /* variable-length */           \
+    union __name##_sring_entry ring[];                                  \
 };                                                                      \
                                                                         \
 /* "Front" end's private variables */                                   \
diff --git a/include/xen/interface/io/sndif.h b/include/xen/interface/io/sndif.h
index 445657cdb1de..b818517588b5 100644
--- a/include/xen/interface/io/sndif.h
+++ b/include/xen/interface/io/sndif.h
@@ -659,7 +659,7 @@ struct xensnd_open_req {
 
 struct xensnd_page_directory {
 	grant_ref_t gref_dir_next_page;
-	grant_ref_t gref[1]; /* Variable length */
+	grant_ref_t gref[];
 };
 
 /*