On 10/15/23 10:42, Michael S. Tsirkin wrote:
> 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
OK, I've just submitted a RFC draft v2 assuming net/vhost-user.c instead
of net-virtio.
>
>>
>>>
>>>> ---
>>>> 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
>>>
>>
>
