[PATCH] virtio-net: Fix probe of virtio-net on kvmtool

[Rob Bradford via B4 Relay]

From: Rob Bradford <rbradford@xxxxxxxxxxxx>

kvmtool does not support the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature
but does advertise the VIRTIO_NET_F_GUEST_TSO{4,6} features. Check that
the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature is present before setting
the NETIF_F_GRO_HW feature bit as otherwise an attempt will be made to
program the virtio-net device using the ctrl queue which will fail.

This resolves the following error when running on kvmtool:

[    1.865992] net eth0: Fail to set guest offload.
[    1.872491] virtio_net virtio2 eth0: set_features() failed (-22); wanted 0x0000000000134829, left 0x0080000000134829

Signed-off-by: Rob Bradford <rbradford@xxxxxxxxxxxx>
---
 drivers/net/virtio_net.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 61e33e4dd0cd..59951e51fe76 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3781,9 +3781,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
 		dev->features |= NETIF_F_RXCSUM;
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
-	    virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6))
-		dev->features |= NETIF_F_GRO_HW;
-	if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS))
+	    virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6) &&
+	    virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS))
 		dev->hw_features |= NETIF_F_GRO_HW;
 
 	dev->vlan_features = dev->features;

---
base-commit: c39cea6f38eefe356d64d0bc1e1f2267e282cdd3
change-id: 20230223-virtio-net-kvmtool-87f37515be22

Best regards,
-- 
Rob Bradford <rbradford@xxxxxxxxxxxx>