[Qemu-devel] [PATCH V2 1/3] virtio: introduce virtqueue_unmap_sg()

[Qemu-devel] [PATCH V2 1/3] virtio: introduce virtqueue_unmap_sg()

[Jason Wang]

Factor out sg unmapping logic. This will be reused by the patch that
can discard descriptor.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Andrew James <andrew.james@hpe.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes from V1:
- Fix use of uninitialized var warning.
---
 hw/virtio/virtio.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 0832db9..bb2c4cf 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -243,14 +243,12 @@ int virtio_queue_empty(VirtQueue *vq)
     return vring_avail_idx(vq) == vq->last_avail_idx;
 }
 
-void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
-                    unsigned int len, unsigned int idx)
+static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
+                               unsigned int len)
 {
     unsigned int offset;
     int i;
 
-    trace_virtqueue_fill(vq, elem, len, idx);
-
     offset = 0;
     for (i = 0; i < elem->in_num; i++) {
         size_t size = MIN(len - offset, elem->in_sg[i].iov_len);
@@ -266,6 +264,14 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
         cpu_physical_memory_unmap(elem->out_sg[i].iov_base,
                                   elem->out_sg[i].iov_len,
                                   0, elem->out_sg[i].iov_len);
+}
+
+void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
+                    unsigned int len, unsigned int idx)
+{
+    trace_virtqueue_fill(vq, elem, len, idx);
+
+    virtqueue_unmap_sg(vq, elem, len);
 
     idx = (idx + vring_used_idx(vq)) % vq->vring.num;
 
-- 
2.1.4

[Qemu-devel] [PATCH V2 2/3] virtio: introduce virtqueue_discard()

[Jason Wang]

This patch introduces virtqueue_discard() to discard a descriptor and
unmap the sgs. This will be used by the patch that will discard
descriptor when packet is truncated.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/virtio.c         | 7 +++++++
 include/hw/virtio/virtio.h | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index bb2c4cf..d24f775 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -266,6 +266,13 @@ static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
                                   0, elem->out_sg[i].iov_len);
 }
 
+void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
+                       unsigned int len)
+{
+    vq->last_avail_idx--;
+    virtqueue_unmap_sg(vq, elem, len);
+}
+
 void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len, unsigned int idx)
 {
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 6201ee8..9d09115 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -146,6 +146,8 @@ void virtio_del_queue(VirtIODevice *vdev, int n);
 void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len);
 void virtqueue_flush(VirtQueue *vq, unsigned int count);
+void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
+                       unsigned int len);
 void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len, unsigned int idx);
 
-- 
2.1.4

[Qemu-devel] [PATCH V2 3/3] virtio-net: correctly drop truncated packets

[Jason Wang]

When packet is truncated during receiving, we drop the packets but
neither discard the descriptor nor add and signal used
descriptor. This will lead several issues:

- sg mappings are leaked
- rx will be stalled if a lots of packets were truncated

In order to be consistent with vhost, fix by discarding the descriptor
in this case.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/net/virtio-net.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index f72eebf..038a18b 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1086,13 +1086,7 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t
          * must have consumed the complete packet.
          * Otherwise, drop it. */
         if (!n->mergeable_rx_bufs && offset < size) {
-#if 0
-            error_report("virtio-net truncated non-mergeable packet: "
-                         "i %zd mergeable %d offset %zd, size %zd, "
-                         "guest hdr len %zd, host hdr len %zd",
-                         i, n->mergeable_rx_bufs,
-                         offset, size, n->guest_hdr_len, n->host_hdr_len);
-#endif
+            virtqueue_discard(q->rx_vq, &elem, total);
             return size;
         }
 
-- 
2.1.4