vhost-net: mergeable buffers support

This adds support for mergeable buffers in vhost-net: this is needed
for older guests without indirect buffer support, as well
as for zero copy with some devices.

Includes changes by Michael S. Tsirkin to make the
patch as low risk as possible (i.e., close to no changes
when feature is disabled).

Signed-off-by: David Stevens <dlstevens@us.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 12 insertions, 5 deletions

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 3693327549b3..afd77295971c 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -96,7 +96,9 @@ struct vhost_virtqueue {
         struct iovec indirect[VHOST_NET_MAX_SG];
         struct iovec iov[VHOST_NET_MAX_SG];
         struct iovec hdr[VHOST_NET_MAX_SG];
-        size_t hdr_size;
+        size_t vhost_hlen;
+        size_t sock_hlen;
+        struct vring_used_elem heads[VHOST_NET_MAX_SG];
         /* We use a kind of RCU to access private pointer.
          * All readers access it from worker, which makes it possible to
          * flush the vhost_work instead of synchronize_rcu. Therefore readers do
@@ -139,12 +141,16 @@ int vhost_get_vq_desc(struct vhost_dev *, struct vhost_virtqueue *,
                       struct iovec iov[], unsigned int iov_count,
                       unsigned int *out_num, unsigned int *in_num,
                       struct vhost_log *log, unsigned int *log_num);
-void vhost_discard_vq_desc(struct vhost_virtqueue *);
+void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
 int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
-void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
+int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
+                     unsigned count);
 void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
-                               unsigned int head, int len);
+                               unsigned int id, int len);
+void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
+                               struct vring_used_elem *heads, unsigned count);
+void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
 void vhost_disable_notify(struct vhost_virtqueue *);
 bool vhost_enable_notify(struct vhost_virtqueue *);
 
@@ -161,7 +167,8 @@ enum {
         VHOST_FEATURES = (1 << VIRTIO_F_NOTIFY_ON_EMPTY) |
                          (1 << VIRTIO_RING_F_INDIRECT_DESC) |
                          (1 << VHOST_F_LOG_ALL) |
-                         (1 << VHOST_NET_F_VIRTIO_NET_HDR),
+                         (1 << VHOST_NET_F_VIRTIO_NET_HDR) |
+                         (1 << VIRTIO_NET_F_MRG_RXBUF),
 };
 
 static inline int vhost_has_feature(struct vhost_dev *dev, int bit)