On Wed, Oct 27, 2021 at 6:00 PM 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 keep both interfaces if the MAC addresses are different
> (to have the same MAC address can cause kernel crash with old
> kernel). The VFIO device will be unplugged before the migration
> like in the normal failover migration but without a failover device.
>
> This patch adds a new property to the virtio-net device:
> "failover-legacy-mac"
>
> If an alternate MAC address is provided with "failover-legacy-mac" and
> the STANDBY feature is not supported, both interfaces are plugged
> but the standby interface (virtio-net) MAC address is set to the
> value provided by the "failover-legacy-mac" parameter.
>
> If the STANDBY feature is supported by guest and QEMU, the virtio-net
> failover acts as usual.
>
> Signed-off-by: Laurent Vivier <lviv...@redhat.com>
Acked-by: Jason Wang <jasow...@redhat.com>
> ---
>
> Notes:
> v2: rename alt-mac to failover-legacy-mac
> update doc with text provided by MST
>
> docs/system/virtio-net-failover.rst | 10 ++++++
> hw/net/virtio-net.c | 48 +++++++++++++++++++++++------
> include/hw/virtio/virtio-net.h | 6 ++++
> 3 files changed, 55 insertions(+), 9 deletions(-)
>
> diff --git a/docs/system/virtio-net-failover.rst
> b/docs/system/virtio-net-failover.rst
> index 6002dc5d96e4..99f21cd55ef7 100644
> --- a/docs/system/virtio-net-failover.rst
> +++ b/docs/system/virtio-net-failover.rst
> @@ -51,6 +51,16 @@ Usage
> is only for pairing the devices within QEMU. The guest kernel module
> net_failover will match devices with identical MAC addresses.
>
> + For legacy guests (including bios/EUFI) not supporting
> VIRTIO_NET_F_STANDBY,
> + two options exist:
> +
> + 1. if failover-legacy-mac has not been configured (default)
> + only the standby virtio-net device is visible to the guest
> +
> + 2. if failover-legacy-mac has been configured, virtio and vfio devices will
> + be presented to guest as two NIC devices, with virtio using the
> + failover-legacy-mac address.
> +
> Hotplug
> -------
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index f2014d5ea0b3..0d47d287de14 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -45,6 +45,9 @@
> #include "net_rx_pkt.h"
> #include "hw/virtio/vhost.h"
>
> +/* zero MAC address to check with */
> +static const MACAddr zero = { .a = { 0, 0, 0, 0, 0, 0 } };
> +
> #define VIRTIO_NET_VM_VERSION 11
>
> #define MAC_TABLE_ENTRIES 64
> @@ -126,7 +129,6 @@ static void virtio_net_get_config(VirtIODevice *vdev,
> uint8_t *config)
> VirtIONet *n = VIRTIO_NET(vdev);
> struct virtio_net_config netcfg;
> NetClientState *nc = qemu_get_queue(n->nic);
> - static const MACAddr zero = { .a = { 0, 0, 0, 0, 0, 0 } };
>
> int ret = 0;
> memset(&netcfg, 0 , sizeof(struct virtio_net_config));
> @@ -871,10 +873,21 @@ static void failover_add_primary(VirtIONet *n, Error
> **errp)
> error_propagate(errp, err);
> }
>
> +static void failover_plug_primary(VirtIONet *n)
> +{
> + Error *err = NULL;
> +
> + 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);
> + }
> +}
> +
> static void virtio_net_set_features(VirtIODevice *vdev, uint64_t features)
> {
> VirtIONet *n = VIRTIO_NET(vdev);
> - Error *err = NULL;
> int i;
>
> if (n->mtu_bypass_backend &&
> @@ -921,12 +934,22 @@ 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 (n->failover) {
> + if (virtio_has_feature(features, VIRTIO_NET_F_STANDBY)) {
> + if (memcmp(&n->legacy_mac, &zero, sizeof(zero)) != 0 &&
> + memcmp(n->mac, &n->legacy_mac, ETH_ALEN) == 0) {
> + /*
> + * set_features can be called twice, without & with
> F_STANDBY,
> + * so restore original MAC address
> + */
> + memcpy(n->mac, &n->nic->conf->macaddr, sizeof(n->mac));
> + qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac);
> + }
> + failover_plug_primary(n);
> + } else if (memcmp(&n->legacy_mac, &zero, sizeof(zero)) != 0) {
> + memcpy(n->mac, &n->legacy_mac, ETH_ALEN);
> + qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac);
> + failover_plug_primary(n);
> }
> }
> }
> @@ -3595,9 +3618,15 @@ static bool primary_unplug_pending(void *opaque)
> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> VirtIONet *n = VIRTIO_NET(vdev);
>
> - if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_STANDBY)) {
> + if (!n->failover) {
> return false;
> }
> +
> + if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_STANDBY) &&
> + memcmp(&n->legacy_mac, &zero, sizeof(zero)) == 0) {
> + return false;
> + }
> +
> primary = failover_find_primary_device(n);
> return primary ? primary->pending_deleted_event : false;
> }
> @@ -3672,6 +3701,7 @@ static Property virtio_net_properties[] = {
> DEFINE_PROP_UINT32("rsc_interval", VirtIONet, rsc_timeout,
> VIRTIO_NET_RSC_DEFAULT_INTERVAL),
> DEFINE_NIC_PROPERTIES(VirtIONet, nic_conf),
> + DEFINE_PROP_MACADDR("failover-legacy-mac", VirtIONet, legacy_mac),
> DEFINE_PROP_UINT32("x-txtimer", VirtIONet, net_conf.txtimer,
> TX_TIMER_INTERVAL),
> DEFINE_PROP_INT32("x-txburst", VirtIONet, net_conf.txburst, TX_BURST),
> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
> index eb87032627d2..4b9523def5fb 100644
> --- a/include/hw/virtio/virtio-net.h
> +++ b/include/hw/virtio/virtio-net.h
> @@ -213,6 +213,12 @@ struct VirtIONet {
> QDict *primary_opts;
> bool primary_opts_from_json;
> Notifier migration_state;
> + /*
> + * failover: to provide an alternate MAC address allows to keep both
> + * cards, primary and stand-by, if the STANDBY feature is not supported
> + * by the guest
> + */
> + MACAddr legacy_mac;
> VirtioNetRssData rss_data;
> struct NetRxPkt *rx_pkt;
> struct EBPFRSSContext ebpf_rss;
> --
> 2.31.1
>
