[PATCH v2 3/4] virtio_test: use random length scatterlists to test descriptor chain

[Guo Zhi]

Prior implementation only use one descriptor for each io event, which
does't test code of descriptor chain. More importantly, one descriptor
will not use indirect feature even indirect feature is specified. Use
random length scatterlists here to test descriptor chain.

Signed-off-by: Guo Zhi <qtxuning1999@xxxxxxxxxxx>
---
 tools/virtio/virtio_test.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/virtio/virtio_test.c b/tools/virtio/virtio_test.c
index 1ecd64271..363695b33 100644
--- a/tools/virtio/virtio_test.c
+++ b/tools/virtio/virtio_test.c
@@ -20,6 +20,7 @@
 #include "../../drivers/vhost/test.h"
 
 #define RANDOM_BATCH -1
+#define MAX_SG_FRAGS 8UL
 #define ALIGN 4096
 #define RINGSIZE   256
 #define TEST_BUF_NUM 0x100000
@@ -172,7 +173,8 @@ static void wait_for_interrupt(struct vdev_info *dev)
 static void run_test(struct vdev_info *dev, struct vq_info *vq,
 		     bool delayed, int batch, int reset_n, int bufs)
 {
-	struct scatterlist sl;
+	struct scatterlist sg[MAX_SG_FRAGS];
+	int sg_size = 0;
 	long started = 0, completed = 0, next_reset = reset_n;
 	long completed_before, started_before;
 	int r, test = 1;
@@ -197,8 +199,11 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq,
 
 			while (started < bufs &&
 			       (started - completed) < batch) {
-				sg_init_one(&sl, dev->buf, dev->buf_size);
-				r = virtqueue_add_outbuf(vq->vq, &sl, 1,
+				sg_size = random() % (MAX_SG_FRAGS - 1) + 1;
+				sg_init_table(sg, sg_size);
+				for (int i = 0; i < sg_size; ++i)
+					sg_set_buf(&sg[i], dev->buf + i, 0x1);
+				r = virtqueue_add_outbuf(vq->vq, sg, sg_size,
 							 dev->buf + started,
 							 GFP_ATOMIC);
 				if (unlikely(r != 0)) {
-- 
2.17.1