Merge tag 'vfio-ccw-20171016' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/vfio-ccw into features

Pull vfio-ccw update from Cornelia Huck:
"Some improvements in data handling for vfio-ccw."

drivers/s390/cio/vfio_ccw_cp.c

@@ -105,7 +105,10 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
 {
 	int ret = 0;
 
-	if (!len || pa->pa_nr)
+	if (!len)
+		return 0;
+
+	if (pa->pa_nr)
 		return -EINVAL;
 
 	pa->pa_iova = iova;
@@ -501,6 +504,16 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
 
 	ccw = chain->ch_ccw + idx;
 
+	if (!ccw->count) {
+		/*
+		 * We just want the translation result of any direct ccw
+		 * to be an IDA ccw, so let's add the IDA flag for it.
+		 * Although the flag will be ignored by firmware.
+		 */
+		ccw->flags |= CCW_FLAG_IDA;
+		return 0;
+	}
+
 	/*
 	 * Pin data page(s) in memory.
 	 * The number of pages actually is the count of the idaws which will be
@@ -541,6 +554,9 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,
 
 	ccw = chain->ch_ccw + idx;
 
+	if (!ccw->count)
+		return 0;
+
 	/* Calculate size of idaws. */
 	ret = copy_from_iova(cp->mdev, &idaw_iova, ccw->cda, sizeof(idaw_iova));
 	if (ret)
@@ -569,10 +585,6 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,
 
 	for (i = 0; i < idaw_nr; i++) {
 		idaw_iova = *(idaws + i);
-		if (IS_ERR_VALUE(idaw_iova)) {
-			ret = -EFAULT;
-			goto out_free_idaws;
-		}
 
 		ret = pfn_array_alloc_pin(pat->pat_pa + i, cp->mdev,
 					  idaw_iova, 1);