On 11/08/2021 06:18, Jason Wang wrote:
> On Tue, Aug 10, 2021 at 1:14 AM Laurent Vivier <lviv...@redhat.com> wrote:
>>
>> If the guest driver doesn't support the STANDBY feature, by default
>> we keep the virtio-net device and don't hotplug the VFIO device,
>> but in some cases, user can prefer to use the VFIO device rather
>> than the virtio-net one. We can't unplug the virtio-net device
>> (because on migration it is expected on the destination side)
>> but we can force the guest driver to be disabled. Then, we can
>> hotplug the VFIO device that will be unplugged before the migration
>> like in the normal failover migration but without the failover device.
>>
>> This patch adds a new property to virtio-net device: "failover-default".
>>
>> By default, "failover-default" is set to true and thus the default NIC
>> to use if the failover cannot be enabled is the virtio-net device
>> (this is what is done until now with the virtio-net failover).
>>
>> If "failover-default" is set to false, in case of error, the virtio-net
>> device is not the default anymore and the failover primary device
>> is used instead.
>>
>> If the STANDBY feature is supported by guest and host, the virtio-net
>> failover acts as usual.
>>
>> Signed-off-by: Laurent Vivier <lviv...@redhat.com>
>> ---
>> include/hw/virtio/virtio-net.h | 1 +
>> hw/net/virtio-net.c | 49 +++++++++++++++++++++++++++++-----
>> 2 files changed, 44 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
>> index 824a69c23f06..ab77930a327e 100644
>> --- a/include/hw/virtio/virtio-net.h
>> +++ b/include/hw/virtio/virtio-net.h
>> @@ -208,6 +208,7 @@ struct VirtIONet {
>> /* primary failover device is hidden*/
>> bool failover_primary_hidden;
>> bool failover;
>> + bool failover_default;
>> DeviceListener primary_listener;
>> Notifier migration_state;
>> VirtioNetRssData rss_data;
>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
>> index 16d20cdee52a..972c03232a96 100644
>> --- a/hw/net/virtio-net.c
>> +++ b/hw/net/virtio-net.c
>> @@ -935,12 +935,23 @@ static void virtio_net_set_features(VirtIODevice
>> *vdev, uint64_t features)
>> memset(n->vlans, 0xff, MAX_VLAN >> 3);
>> }
>>
>> - if (virtio_has_feature(features, VIRTIO_NET_F_STANDBY)) {
>> - qapi_event_send_failover_negotiated(n->netclient_name);
>> - qatomic_set(&n->failover_primary_hidden, false);
>> - failover_add_primary(n, &err);
>> - if (err) {
>> - warn_report_err(err);
>> + /*
>> + * if the virtio-net driver has the STANDBY feature, we can plug the
>> primary
>> + * if not but is not the default failover device,
>> + * we need to plug the primary alone and the virtio-net driver will
>> + * be disabled in the validate_features() function but
>> validate_features()
>> + * is only available with virtio 1.0 spec
>> + */
>> + if (n->failover) {
>> + if (virtio_has_feature(features, VIRTIO_NET_F_STANDBY) ||
>> + (virtio_has_feature(features, VIRTIO_F_VERSION_1) &&
>
> I think STANDY implies VERSION_1.
>
> And if we do this, it means it doesn't work for legacy drivers.
>
> Not sure if it's an issue.
Yes, you're right. In case of a kernel driver that doesn't support STANDBY and
that is not
version 1, the virtio-net device is disabled (and the VFIO device is not
plugged).
Thanks,
Laurent
