On Sat, Oct 14, 2023 at 09:06:09PM +0000, Vincent Jardin wrote:
> On 10/14/23 18:37, Michael S. Tsirkin wrote:
> > On Sat, Oct 14, 2023 at 06:22:34PM +0200, Vincent Jardin wrote:
> >> Using interface's settings, let's enforce an always on link up.
> >>
> >> Signed-off-by: Vincent Jardin <vincent.jar...@ekinops.com>
> >
> > What is going on here? Just don't set it down.
>
> The purpose is to have a stable vLink for the VMs that don't support
> such sysctl arp_evict_nocarrier:
> https://patchwork.kernel.org/project/netdevbpf/patch/20211101173630.300969-2-prest...@gmail.com/
>
> We are facing some users of vSwitches that use vhost-user and that
> disconnect and reconnect during some operations. For most of the VMs on
> their deployments with such vSwitches, those VMs' vLink should not flap.
>
> For those VMs, the flaps are critical and they can lead to some
> convergence issues.
>
> If this capability is not at the virtio-net level, should it be at
> qemu's net_vhost_user_event() ?
> For instance, from
> https://github.com/qemu/qemu/blob/63011373ad22c794a013da69663c03f1297a5c56/net/vhost-user.c#L266
>
> ?
>
> best regards,
> Vincent
makes sense
>
> >
> >> ---
> >> hw/net/virtio-net.c | 8 ++++++++
> >> include/hw/virtio/virtio-net.h | 2 ++
> >> 2 files changed, 10 insertions(+)
> >>
> >> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >> index 29e33ea5ed..e731b4fdea 100644
> >> --- a/hw/net/virtio-net.c
> >> +++ b/hw/net/virtio-net.c
> >> @@ -78,6 +78,9 @@
> >> tso/gso/gro 'off'. */
> >> #define VIRTIO_NET_RSC_DEFAULT_INTERVAL 300000
> >>
> >> +/* force always link up */
> >> +#define VIRTIO_NET_LINK_UP false
> >> +
> >> #define VIRTIO_NET_RSS_SUPPORTED_HASHES (VIRTIO_NET_RSS_HASH_TYPE_IPv4 |
> >> \
> >> VIRTIO_NET_RSS_HASH_TYPE_TCPv4
> >> | \
> >> VIRTIO_NET_RSS_HASH_TYPE_UDPv4
> >> | \
> >> @@ -447,6 +450,9 @@ static void virtio_net_set_link_status(NetClientState
> >> *nc)
> >> else
> >> n->status |= VIRTIO_NET_S_LINK_UP;
> >>
> >> + if (n->net_conf.link_up)
> >> + n->status |= VIRTIO_NET_S_LINK_UP;
> >> +
> >> if (n->status != old_status)
> >> virtio_notify_config(vdev);
> >>
> >> @@ -3947,6 +3953,8 @@ static Property virtio_net_properties[] = {
> >> VIRTIO_NET_F_GUEST_USO6, true),
> >> DEFINE_PROP_BIT64("host_uso", VirtIONet, host_features,
> >> VIRTIO_NET_F_HOST_USO, true),
> >> + DEFINE_PROP_BOOL("link_up", VirtIONet, net_conf.link_up,
> >> + VIRTIO_NET_LINK_UP),
> >> DEFINE_PROP_END_OF_LIST(),
> >> };
> >>
> >> diff --git a/include/hw/virtio/virtio-net.h
> >> b/include/hw/virtio/virtio-net.h
> >> index 55977f01f0..385bebab34 100644
> >> --- a/include/hw/virtio/virtio-net.h
> >> +++ b/include/hw/virtio/virtio-net.h
> >> @@ -56,6 +56,7 @@ typedef struct virtio_net_conf
> >> char *duplex_str;
> >> uint8_t duplex;
> >> char *primary_id_str;
> >> + bool link_up; /* if set enforce link up, never down */
> >> } virtio_net_conf;
> >>
> >> /* Coalesced packets type & status */
> >> @@ -180,6 +181,7 @@ struct VirtIONet {
> >> size_t guest_hdr_len;
> >> uint64_t host_features;
> >> uint32_t rsc_timeout;
> >> + uint32_t link_up; /* if set enforce link up, never down */
> >> uint8_t rsc4_enabled;
> >> uint8_t rsc6_enabled;
> >> uint8_t has_ufo;
> >> --
> >> 2.34.1
> >
>
