vfio/ccw: pass page count to page_array struct

The allocation of our page_array struct calculates the number
of 4K pages that would be needed to hold a certain number of
bytes. But, since the number of pages that will be pinned is
also calculated by the length of the IDAL, this logic is
unnecessary. Let's pass that information in directly, and
avoid the math within the allocator.

Also, let's make this two allocations instead of one,
to make it apparent what's happening within here.
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

drivers/s390/cio/vfio_ccw_cp.c

@@ -43,7 +43,7 @@ struct ccwchain {
  * page_array_alloc() - alloc memory for page array
  * @pa: page_array on which to perform the operation
  * @iova: target guest physical address
- * @len: number of bytes that should be pinned from @iova
+ * @len: number of pages that should be pinned from @iova
  *
  * Attempt to allocate memory for page array.
  *
@@ -63,18 +63,20 @@ static int page_array_alloc(struct page_array *pa, u64 iova, unsigned int len)
 	if (pa->pa_nr || pa->pa_iova)
 		return -EINVAL;
 
-	pa->pa_nr = ((iova & ~PAGE_MASK) + len + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
-	if (!pa->pa_nr)
+	if (len == 0)
 		return -EINVAL;
 
-	pa->pa_iova = kcalloc(pa->pa_nr,
-			      sizeof(*pa->pa_iova) + sizeof(*pa->pa_page),
-			      GFP_KERNEL);
-	if (unlikely(!pa->pa_iova)) {
-		pa->pa_nr = 0;
+	pa->pa_nr = len;
+
+	pa->pa_iova = kcalloc(len, sizeof(*pa->pa_iova), GFP_KERNEL);
+	if (!pa->pa_iova)
+		return -ENOMEM;
+
+	pa->pa_page = kcalloc(len, sizeof(*pa->pa_page), GFP_KERNEL);
+	if (!pa->pa_page) {
+		kfree(pa->pa_iova);
 		return -ENOMEM;
 	}
-	pa->pa_page = (struct page **)&pa->pa_iova[pa->pa_nr];
 
 	pa->pa_iova[0] = iova;
 	pa->pa_page[0] = NULL;
@@ -167,6 +169,7 @@ static int page_array_pin(struct page_array *pa, struct vfio_device *vdev)
 static void page_array_unpin_free(struct page_array *pa, struct vfio_device *vdev)
 {
 	page_array_unpin(pa, vdev, pa->pa_nr);
+	kfree(pa->pa_page);
 	kfree(pa->pa_iova);
 }
 
@@ -545,7 +548,7 @@ static int ccwchain_fetch_ccw(struct ccw1 *ccw,
 	 * required for the data transfer, since we only only support
 	 * 4K IDAWs today.
 	 */
-	ret = page_array_alloc(pa, iova, bytes);
+	ret = page_array_alloc(pa, iova, idaw_nr);
 	if (ret < 0)
 		goto out_free_idaws;