[Qemu-devel] Re: [PATCH v2 4/8] qemu:virtio-net: Add a virtqueue for control commands from the guest

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

On Tue, 2009-02-03 at 14:56 -0600, Anthony Liguori wrote:
> Alex Williamson wrote:
> > +        ctrl = elem.out_sg[0].iov_base;
> > +        status = elem.in_sg[elem.in_num - 1].iov_base;
> >   
> 
> This works only because we're dealing with uint8_ts but it's broken 
> elsewhere in virtio-net.  iov_base is guest memory which means it may 
> have different endianness.  We really should be using ldub_p() here.
> 
> > +        *status = VIRTIO_NET_ERR;
> >   
> 
> And stb_p() here.

Thanks Anthony.  So before I patch bomb again, I think this turns into
something like below.  This makes the struct definitions less useful on
the backend side, but I'm not sure we can do anything about that.  I
assume for u16s and u32s used in other parts of the interface, we'll
define those as little endian, which means the guest side driver
eventually needs a follow-up patch for big endian archs.  Thanks,

Alex


qemu:virtio-net: Add a virtqueue for control commands from the guest

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>
---

 hw/virtio-net.c |   34 +++++++++++++++++++++++++++++++++-
 hw/virtio-net.h |   18 ++++++++++++++++++
 2 files changed, 51 insertions(+), 1 deletions(-)


diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 073f23a..7971f95 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -25,6 +25,7 @@ typedef struct VirtIONet
     uint16_t status;
     VirtQueue *rx_vq;
     VirtQueue *tx_vq;
+    VirtQueue *ctrl_vq;
     VLANClientState *vc;
     QEMUTimer *tx_timer;
     int tx_timer_active;
@@ -79,7 +80,9 @@ static void virtio_net_set_link_status(VLANClientState *vc)
 
 static uint32_t virtio_net_get_features(VirtIODevice *vdev)
 {
-    uint32_t features = (1 << VIRTIO_NET_F_MAC) | (1 << VIRTIO_NET_F_STATUS);
+    uint32_t features = (1 << VIRTIO_NET_F_MAC) |
+                        (1 << VIRTIO_NET_F_STATUS) |
+                        (1 << VIRTIO_NET_F_CTRL_VQ);
 
     return features;
 }
@@ -91,6 +94,34 @@ static void virtio_net_set_features(VirtIODevice *vdev, uint32_t features)
     n->mergeable_rx_bufs = !!(features & (1 << VIRTIO_NET_F_MRG_RXBUF));
 }
 
+static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
+{
+    struct virtio_net_ctrl_hdr ctrl;
+    virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
+    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.class = ldub_p(elem.out_sg[0].iov_base);
+        ctrl.cmd = ldub_p(elem.out_sg[0].iov_base + sizeof(ctrl.class));
+
+        stb_p(elem.in_sg[elem.in_num - 1].iov_base, status);
+
+        virtqueue_push(vq, &elem, sizeof(status));
+        virtio_notify(vdev, vq);
+    }
+}
+
 /* RX */
 
 static void virtio_net_handle_rx(VirtIODevice *vdev, VirtQueue *vq)
@@ -356,6 +387,7 @@ void 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/hw/virtio-net.h b/hw/virtio-net.h
index 9dce663..119e38d 100644
--- a/hw/virtio-net.h
+++ b/hw/virtio-net.h
@@ -40,6 +40,7 @@
 #define VIRTIO_NET_F_HOST_UFO   14      /* Host can handle UFO in. */
 #define VIRTIO_NET_F_MRG_RXBUF  15      /* Host can merge receive buffers. */
 #define VIRTIO_NET_F_STATUS     16      /* virtio_net_config.status available */
+#define VIRTIO_NET_F_CTRL_VQ    17      /* Control channel available */
 
 #define VIRTIO_NET_S_LINK_UP    1       /* Link is up */
 
@@ -84,4 +85,21 @@ struct virtio_net_hdr_mrg_rxbuf
 
 void 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