Re: [Qemu-devel] Headsup: windows virtio networking does not work on current git

[Michael S. Tsirkin]

On Sun, Feb 03, 2013 at 03:09:39PM -0600, Anthony Liguori wrote:
> Michael Tokarev <address@hidden> writes:
> 
> > 03.02.2013 17:23, Yan Vugenfirer wrote:
> >
> >>> If it helps, mq changes the config size from 8 to 16 bytes.  If the
> >>> driver was making an assumption about an 8-byte config size, that's
> >>> likely what the problem is.
> >>>
> >> That's exactly the problem.
> >
> > So what do we do?  It isn't nice to break existing setups.
> > Maybe mq can be disabled by default (together with Antony's
> > patch) until fixed drivers will be more widely available?
> 
> I've got a patch that does exactly like this.  It's pretty ugly though
> because of the relationship between virtio-pci and virtio-net.  I'm
> going to try to see if I can find a cleaner way to do it on Monday.
> 
> I'm also contemplating just disabling mq by default.  Since a special
> command line is needed to enable it anyway (on the backend), having to
> specify mq=on for the device doesn't seem so bad.


It's after midnight here so didn't test yet, but wouldn't the following
achieve this in a way that is a bit cleaner?

Signed-off-by: Michael S. Tsirkin <address@hidden>


diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 5699f5e..3342a76 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -346,6 +346,10 @@ static uint32_t virtio_net_get_features(VirtIODevice 
*vdev, uint32_t features)
 
     features |= (1 << VIRTIO_NET_F_MAC);
 
+    if (n->max_queues <= 1) {
+        features &= ~(0x1 << VIRTIO_NET_F_MQ);
+    }
+
     if (!peer_has_vnet_hdr(n)) {
         features &= ~(0x1 << VIRTIO_NET_F_CSUM);
         features &= ~(0x1 << VIRTIO_NET_F_HOST_TSO4);
@@ -1284,7 +1288,9 @@ VirtIODevice *virtio_net_init(DeviceState *dev, NICConf 
*conf,
     int i;
 
     n = (VirtIONet *)virtio_common_init("virtio-net", VIRTIO_ID_NET,
-                                        sizeof(struct virtio_net_config),
+                                        conf->queues > 1 ?
+                                            sizeof(struct virtio_net_config) :
+                                            sizeof(struct 
virtio_net_config_compat),
                                         sizeof(VirtIONet));
 
     n->vdev.get_config = virtio_net_get_config;
diff --git a/hw/virtio-net.h b/hw/virtio-net.h
index 1d5c721..95ad54f 100644
--- a/hw/virtio-net.h
+++ b/hw/virtio-net.h
@@ -69,6 +69,15 @@ typedef struct virtio_net_conf
 /* Maximum packet size we can receive from tap device: header + 64k */
 #define VIRTIO_NET_MAX_BUFSIZE (sizeof(struct virtio_net_hdr) + (64 << 10))
 
+
+struct virtio_net_config_compat
+{
+    /* The config defining mac address ($ETH_ALEN bytes) */
+    uint8_t mac[ETH_ALEN];
+    /* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
+    uint16_t status;
+} QEMU_PACKED;
+
 struct virtio_net_config
 {
     /* The config defining mac address ($ETH_ALEN bytes) */