[libvirt] [v2 RESEND PATCH] qemu: reduce packet loss rate for vm with macvtap passthrough mode in migration

[Laine Stump]

On 06/14/2017 04:29 AM, ZhiPeng Lu wrote:
> Before libvirt that calls virNetDevMacVLanCreateWithVPortProfile sets mac address
> or vlan of a Virtual Function(VF) linked to a macvtap passthrough device of migration
> destination host in migration start step. If we ping the migrating vm,
> we get the network does not pass. Because VFs of migration source and destination
> have the same MAC address. The patch later calling qemuMigrationVPAssociatePortProfiles
> sets mac address of VF in migration finish step instead of start step.
> The patch aims to reduce packet loss rate.

I missed this patch when you initially sent it, and see that nobody else
responded...


What you're doing here shouldn't be needed. During migration, a macvtap
device should be created with ~IFF_UP, and not brought online until
qemuInterfaceStartDevice() is called just prior to starting the guest
CPUs on the destination; by this time the guest CPUs on the source have
already been stopped (and the guest's macvtap interfaces on the source
have been set offline). Until a device is IFF_UP, it shouldn't send out
any traffic with its MAC address.

If you look at the macvtap device on the destination and it has IFF_UP
set prior to the completion of migration, then there is a bug in libvirt
that we need to fix. Otherwise, I think any packet loss you're seeing is
coming from something else.


>
> Signed-off-by: ZhiPeng Lu <lu.zhipeng at zte.com.cn>
> ---
>  src/qemu/qemu_migration.c   | 18 ++++++++++++++++--
>  src/util/virnetdevmacvlan.c | 17 +++++++++++------
>  2 files changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
> index 09adb04..795ed71 100644
> --- a/src/qemu/qemu_migration.c
> +++ b/src/qemu/qemu_migration.c
> @@ -5004,7 +5004,7 @@ qemuMigrationPerform(virQEMUDriverPtr driver,
>  }
>  
>  static int
> -qemuMigrationVPAssociatePortProfiles(virDomainDefPtr def)
> +qemuMigrationVPAssociatePortProfiles(virDomainDefPtr def, const char *stateDir)
>  {
>      size_t i;
>      int last_good_net = -1;
> @@ -5013,6 +5013,20 @@ qemuMigrationVPAssociatePortProfiles(virDomainDefPtr def)
>      for (i = 0; i < def->nnets; i++) {
>          net = def->nets[i];
>          if (virDomainNetGetActualType(net) == VIR_DOMAIN_NET_TYPE_DIRECT) {
> +            if ((!virDomainNetGetActualVirtPortProfile(net) || (virDomainNetGetActualVirtPortProfile(net) &&
> +                 virDomainNetGetActualVirtPortProfile(net)->virtPortType != VIR_NETDEV_VPORT_PROFILE_8021QBG &&
> +                virDomainNetGetActualVirtPortProfile(net)->virtPortType != VIR_NETDEV_VPORT_PROFILE_8021QBH)) &&
> +                virDomainNetGetActualDirectMode(net) ==
> +                 VIR_NETDEV_MACVLAN_MODE_PASSTHRU) {
> +                if (virNetDevSaveNetConfig(virDomainNetGetActualDirectDev(net),
> +                    -1, stateDir, false) < 0) {
> +                    goto err_exit;
> +                }
> +                if (virNetDevSetNetConfig(virDomainNetGetActualDirectDev(net),
> +                    -1, NULL, virDomainNetGetActualVlan(net), &net->mac, false) < 0) {
> +                    goto err_exit;
> +                }
> +            }
>              if (virNetDevVPortProfileAssociate(net->ifname,
>                                                 virDomainNetGetActualVirtPortProfile(net),
>                                                 &net->mac,
> @@ -5187,7 +5201,7 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
>          goto endjob;
>      }
>  
> -    if (qemuMigrationVPAssociatePortProfiles(vm->def) < 0)
> +    if (qemuMigrationVPAssociatePortProfiles(vm->def, cfg->stateDir) < 0)
>          goto endjob;
>  
>      if (mig->network && qemuDomainMigrateOPDRelocate(driver, vm, mig) < 0)
> diff --git a/src/util/virnetdevmacvlan.c b/src/util/virnetdevmacvlan.c
> index 7222b0f..682dcd1 100644
> --- a/src/util/virnetdevmacvlan.c
> +++ b/src/util/virnetdevmacvlan.c
> @@ -1020,12 +1020,17 @@ virNetDevMacVLanCreateWithVPortProfile(const char *ifnameRequested,
>               */
>              setVlan = false;
>          }
> -
> -        if (virNetDevSaveNetConfig(linkdev, -1, stateDir, setVlan) < 0)
> -           return -1;
> -
> -        if (virNetDevSetNetConfig(linkdev, -1, NULL, vlan, macaddress, setVlan) < 0)
> -           return -1;
> +        if (vmOp != VIR_NETDEV_VPORT_PROFILE_OP_MIGRATE_IN_START &&
> +            virtPortProfile && (virtPortProfile->virtPortType == VIR_NETDEV_VPORT_PROFILE_8021QBH ||
> +            virtPortProfile->virtPortType == VIR_NETDEV_VPORT_PROFILE_8021QBG)) {
> +            if (virNetDevSaveNetConfig(linkdev, -1, stateDir, setVlan) < 0) {
> +                return -1;
> +            }
> +            if (virNetDevSetNetConfig(linkdev, -1, NULL, vlan, macaddress,
> +                setVlan) < 0) {
> +                return -1;
> +            }
> +        }
>      }
>  
>      if (ifnameRequested) {