On 11/17/2016 11:38 PM, Michael S. Tsirkin wrote:
On Thu, Nov 17, 2016 at 10:58:07PM +0100, Maxime Coquelin wrote:
If negotiated, virtio-net gets the advised MTU from vhost-net,
and provides it to the guest through a new virtio_net_config
entry.
Cc: Michael S. Tsirkin <m...@redhat.com>
Cc: Aaron Conole <acon...@redhat.com
Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
hw/net/virtio-net.c | 14 ++++++++++++++
include/hw/virtio/virtio-net.h | 1 +
2 files changed, 15 insertions(+)
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 5009533..36843fe 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -55,6 +55,8 @@ static VirtIOFeature feature_sizes[] = {
.end = endof(struct virtio_net_config, status)},
{.flags = 1 << VIRTIO_NET_F_MQ,
.end = endof(struct virtio_net_config, max_virtqueue_pairs)},
+ {.flags = 1 << VIRTIO_NET_F_MTU,
+ .end = endof(struct virtio_net_config, mtu)},
{}
};
@@ -81,6 +83,7 @@ static void virtio_net_get_config(VirtIODevice *vdev, uint8_t
*config)
virtio_stw_p(vdev, &netcfg.status, n->status);
virtio_stw_p(vdev, &netcfg.max_virtqueue_pairs, n->max_queues);
+ virtio_stw_p(vdev, &netcfg.mtu, n->mtu);
memcpy(netcfg.mac, n->mac, ETH_ALEN);
memcpy(config, &netcfg, n->config_size);
}
@@ -636,6 +639,14 @@ static void virtio_net_set_features(VirtIODevice *vdev,
uint64_t features)
} else {
memset(n->vlans, 0xff, MAX_VLAN >> 3);
}
+
+ if (virtio_has_feature(features, VIRTIO_NET_F_MTU)) {
+ NetClientState *nc = qemu_get_queue(n->nic);
+
+ if (get_vhost_net(nc->peer)) {
+ n->mtu = vhost_net_get_mtu(get_vhost_net(nc->peer));
This means migration breaks silently if you move from a bigger to
smaller mtu. We don't necessarily have to make it work,
but it should be detected and reported.
Good point.
I planned to investigate migration case while looking deeper at
vhost-user versionning topic.
Moving from bigger to smaller MTU is indeed a problem, because the
backend may not support received buffer size.
Isn't also a problem when moving from smaller to bigger MTU, as it no
more respect the contract old host negotiated with the guest?
+ }
+ }
}
static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd,
What about non-vhost traffic? You need to ensure guest does
not get bigger packets.
Ok, do you confirm checking in virtio_net_receive() that buffer size is
smaller or equal than MTU is enough?
@@ -1695,6 +1706,7 @@ static void virtio_net_set_config_size(VirtIONet *n,
uint64_t host_features)
{
int i, config_size = 0;
virtio_add_feature(&host_features, VIRTIO_NET_F_MAC);
+ virtio_add_feature(&host_features, VIRTIO_NET_F_MTU);
for (i = 0; feature_sizes[i].flags != 0; i++) {
if (host_features & feature_sizes[i].flags) {
config_size = MAX(feature_sizes[i].end, config_size);
@@ -1922,6 +1934,8 @@ static Property virtio_net_properties[] = {
DEFINE_PROP_STRING("tx", VirtIONet, net_conf.tx),
DEFINE_PROP_UINT16("rx_queue_size", VirtIONet, net_conf.rx_queue_size,
VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE),
+ DEFINE_PROP_BIT("host_mtu", VirtIONet, host_features,
+ VIRTIO_NET_F_MTU, true),
DEFINE_PROP_END_OF_LIST(),
};
Cross version migration support is missing here.
Sorry, I'm not sure to understand what you expect here.
Could you please provide more details?
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index 0ced975..b6394c8 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -96,6 +96,7 @@ typedef struct VirtIONet {
QEMUTimer *announce_timer;
int announce_counter;
bool needs_vnet_hdr_swap;
+ uint16_t mtu;
} VirtIONet;
void virtio_net_set_netclient_name(VirtIONet *n, const char *name,
--
2.7.4
Thanks,
Maxime
