[Qemu-devel] [PATCH 3/7] qemu:virtio-net: Add a virtqueue for control commands from the guest

[Alex Williamson <alex.williamson@hp.com>]

This will be used for RX mode, MAC table, VLAN table control, etc...

The control transaction consists of one or more "out" sg entries and
one or more "in" sg entries.  The first out entry contains a header
defining the class and command.  Additional out entries may provide
data for the command.  A response via the ack entry is required
and the guest will typically be waiting for it.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
---

 qemu/hw/virtio-net.c |   29 +++++++++++++++++++++++++++++
 qemu/hw/virtio-net.h |   17 +++++++++++++++++
 2 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/qemu/hw/virtio-net.c b/qemu/hw/virtio-net.c
index 44827bc..3d8cba7 100644
--- a/qemu/hw/virtio-net.c
+++ b/qemu/hw/virtio-net.c
@@ -32,6 +32,7 @@ typedef struct VirtIONet
     uint16_t status;
     VirtQueue *rx_vq;
     VirtQueue *tx_vq;
+    VirtQueue *ctrl_vq;
     VLANClientState *vc;
     QEMUTimer *tx_timer;
     int tx_timer_active;
@@ -130,6 +131,33 @@ static void virtio_net_set_features(VirtIODevice *vdev, uint32_t features)
 #endif
 }
 
+static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
+{
+    struct virtio_net_ctrl_hdr *ctrl;
+    virtio_net_ctrl_ack *status;
+    VirtQueueElement elem;
+
+    while (virtqueue_pop(vq, &elem)) {
+        if ((elem.in_num < 1) | (elem.out_num < 1)) {
+            fprintf(stderr, "virtio-net ctrl missing headers\n");
+            exit(1);
+        }
+
+        if (elem.out_sg[0].iov_len < sizeof(*ctrl) ||
+            elem.out_sg[elem.in_num - 1].iov_len < sizeof(*status)) {
+            fprintf(stderr, "virtio-net ctrl header not in correct element\n");
+            exit(1);
+        }
+
+        ctrl = elem.out_sg[0].iov_base;
+        status = elem.in_sg[elem.in_num - 1].iov_base;
+        *status = VIRTIO_NET_ERR;
+
+        virtqueue_push(vq, &elem, sizeof(*status));
+        virtio_notify(vdev, vq);
+    }
+}
+
 /* RX */
 
 static void virtio_net_handle_rx(VirtIODevice *vdev, VirtQueue *vq)
@@ -458,6 +486,7 @@ PCIDevice *virtio_net_init(PCIBus *bus, NICInfo *nd, int devfn)
     n->vdev.set_features = virtio_net_set_features;
     n->rx_vq = virtio_add_queue(&n->vdev, 256, virtio_net_handle_rx);
     n->tx_vq = virtio_add_queue(&n->vdev, 256, virtio_net_handle_tx);
+    n->ctrl_vq = virtio_add_queue(&n->vdev, 16, virtio_net_handle_ctrl);
     memcpy(n->mac, nd->macaddr, ETH_ALEN);
     n->status = VIRTIO_NET_S_LINK_UP;
     n->vc = qemu_new_vlan_client(nd->vlan, nd->model, nd->name,
diff --git a/qemu/hw/virtio-net.h b/qemu/hw/virtio-net.h
index 9ac9e34..9a9641e 100644
--- a/qemu/hw/virtio-net.h
+++ b/qemu/hw/virtio-net.h
@@ -82,4 +82,21 @@ struct virtio_net_hdr_mrg_rxbuf
 
 PCIDevice *virtio_net_init(PCIBus *bus, NICInfo *nd, int devfn);
 
+/*
+ * Control virtqueue data structures
+ *
+ * The control virtqueue expects a header in the first sg entry
+ * and an ack/status response in the last entry.  Data for the
+ * command goes in between.
+ */
+struct virtio_net_ctrl_hdr {
+    uint8_t class;
+    uint8_t cmd;
+};
+
+typedef uint8_t virtio_net_ctrl_ack;
+
+#define VIRTIO_NET_OK     0
+#define VIRTIO_NET_ERR    1
+
 #endif