When TAP_VNET_HDR eventually merges into upstream QEMU, it cannot change the
format of the version 6 savevm data.  This means that we're going to have to
bump the version up to 7.  I'm happy to reserve version 7 as having TAP_VNET_HDR
support to allow time to include this support in upstream QEMU.

For those shipping products based on KVM though, it's important that we do not
conflict with upstream QEMU versioning or else it's going to result in breakage
of backwards compatibility.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 09e4b89..27620ba 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -21,7 +21,12 @@
 
 #define TAP_VNET_HDR
 
-#define VIRTIO_NET_VM_VERSION    6
+/* Version 7 has TAP_VNET_HDR support.  This is reserved in upstream QEMU to
+ * avoid future conflict.
+ * We can't assume verisons > 7 have TAP_VNET_HDR support until this is merged
+ * in upstream QEMU.
+ */
+#define VIRTIO_NET_VM_VERSION    7
 
 #define MAC_TABLE_ENTRIES    32
 #define MAX_VLAN    (1 << 12)   /* Per 802.1Q definition */
@@ -652,8 +657,9 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
         qemu_get_buffer(f, (uint8_t *)n->vlans, MAX_VLAN >> 3);
 
 #ifdef TAP_VNET_HDR
-    if (qemu_get_be32(f))
+    if (version_id == 7 && qemu_get_be32(f)) {
         tap_using_vnet_hdr(n->vc->vlan->first_client, 1);
+    }
 #endif
 
     if (n->tx_timer_active) {
-- 
1.6.0.6

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