vfio/ccw: populate page_array struct inline

There are two possible ways the list of addresses that get passed
to vfio are calculated. One is from a guest IDAL, which would be
an array of (probably) non-contiguous addresses. The other is
built from contiguous pages that follow the starting address
provided by ccw->cda.

page_array_alloc() attempts to simplify things by pre-populating
this array from the starting address, but that's not needed for
a CCW with an IDAL anyway so doesn't need to be in the allocator.
Move it to the caller in the non-IDAL case, since it will be
overwritten when reading the guest IDAL.

Remove the initialization of the pa_page output pointers,
since it won't be explicitly needed for either case.
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

@@ -42,7 +42,6 @@ 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 pages that should be pinned from @iova
  *
  * Attempt to allocate memory for page array.
@@ -56,10 +55,8 @@ struct ccwchain {
  *   -EINVAL if pa->pa_nr is not initially zero, or pa->pa_iova is not NULL
  *   -ENOMEM if alloc failed
  */
-static int page_array_alloc(struct page_array *pa, u64 iova, unsigned int len)
+static int page_array_alloc(struct page_array *pa, unsigned int len)
 {
-	int i;
-
 	if (pa->pa_nr || pa->pa_iova)
 		return -EINVAL;
 
@@ -78,13 +75,6 @@ static int page_array_alloc(struct page_array *pa, u64 iova, unsigned int len)
 		return -ENOMEM;
 	}
 
-	pa->pa_iova[0] = iova;
-	pa->pa_page[0] = NULL;
-	for (i = 1; i < pa->pa_nr; i++) {
-		pa->pa_iova[i] = pa->pa_iova[i - 1] + PAGE_SIZE;
-		pa->pa_page[i] = NULL;
-	}
-
 	return 0;
 }
 
@@ -548,7 +538,7 @@ 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, idaw_nr);
+	ret = page_array_alloc(pa, idaw_nr);
 	if (ret < 0)
 		goto out_free_idaws;
 
@@ -565,11 +555,9 @@ static int ccwchain_fetch_ccw(struct ccw1 *ccw,
 		for (i = 0; i < idaw_nr; i++)
 			pa->pa_iova[i] = idaws[i];
 	} else {
-		/*
-		 * No action is required here; the iova addresses in page_array
-		 * were initialized sequentially in page_array_alloc() beginning
-		 * with the contents of ccw->cda.
-		 */
+		pa->pa_iova[0] = iova;
+		for (i = 1; i < pa->pa_nr; i++)
+			pa->pa_iova[i] = pa->pa_iova[i - 1] + PAGE_SIZE;
 	}
 
 	if (ccw_does_data_transfer(ccw)) {