V1: https://www.redhat.com/archives/libvir-list/2020-January/msg00813.html This all used different names in V1 - in that incarnation the configuration was done using "failover" and "backupAlias" attributes added to the <driver> subelement of <interface>. But the resulting code was cumbersome and had little bits scattered all over the place due to needing it in both hostdev and interface parsing/formatting. In his review of V1, danpb suggesting just adding a new subelement for this configuration to free ourselves from the constraints of <driver> parsing/formatting. This ended up dramatically simplifying the code (hence the lack of V1's refactoring patches in V2, and a decrease in patch count from 12 to 6). During further discussion in email and on IRC, we decided that naming the element <failover> was too limiting, as it implied the behavior of what is, to libvirt, just two network devices that should be teamed/bonded together - it's completely up to the hypervisor and guest what is done with this information. In light of that, we decided to name the new subelement <teaming>, and to specify the two interfaces as "persistent" (an interface that will always remain plugged in) and "transient" (an interface that may be periodically unplugged (during migration, in the case of QEMU). So the virtio device will have <teaming type='persistent'/> and the hostdev device will have <teaming type='transient' persistent='ua-myvirtio'/> (note that the persistent interface must have <alias name='ua-myvirtio'/>) Given this config, libvirt will add "failover=on" to the device commandline arg for the virtio device, and "failover_pair_id=ua-myvirtio" to the arg for the hostdev device (and when a migration is requested, it will notice if there is a hostdev that has <teaming type='transient'/> set, and will allow the migration in this case, but still disallow migrations of domains with normal hostdevs). In response to these extra commandline options, QEMU will set some extra capabilities in the virtio device PCI capabilities data, and will also automatically unplug/re-plug the hostdev device before and after migration. In the guest, the virtio-net driver will notice the extra PCI capabilities and use this as a clue that it should search for another device with matching MAC address (NB: the guest driver requires the two devices to have matching MAC addresses) to join into a bond with the virtio-net device. This bond is hard-wired to always prefer the hostdev device whenever it is present, and use the virtio device as backup when the hostdev is unplugged. ---- As mentioned in a followup to the V1 cover letter, there is a regression in QEMU 4.2.0 that causes QEMU to segv when a hostdev is unplugged. That bug is fixed with this upstream QEMU patch: https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0446f8121723b134ca1d1ed0b73e96d4a0a8689d;hp=48008198270e3ebcc9394401d676c54ed5ac139c Be sure to use a qemu build with this patch applied, or you may not even be able to start the guest! Also we've found that the DEVICE_DELETED event is never sent to libvirt when one of these hostdevs is manually unplugged, meaning that libvirt keeps the device marked as "in-use", and it therefore cannot be re-plugged to the guest until after a complete guest "power cycle". AFAIK there isn't yet a fix for that bug, so don't expect manual unplug of the device to work. Laine Stump (6): qemu: add capabilities flag for failover feature conf: parse/format <teaming> subelement of <interface> qemu: support interface <teaming> functionality qemu: allow migration with assigned PCI hostdev if <teaming> is set qemu: add wait-unplug to qemu migration status enum docs: document <interface> subelement <teaming> docs/formatdomain.html.in | 100 ++++++++++++++++++ docs/news.xml | 28 +++++ docs/schemas/domaincommon.rng | 19 ++++ src/conf/domain_conf.c | 45 ++++++++ src/conf/domain_conf.h | 14 +++ src/qemu/qemu_capabilities.c | 4 + src/qemu/qemu_capabilities.h | 3 + src/qemu/qemu_command.c | 9 ++ src/qemu/qemu_domain.c | 36 ++++++- src/qemu/qemu_migration.c | 53 +++++++++- src/qemu/qemu_monitor.c | 1 + src/qemu/qemu_monitor.h | 1 + src/qemu/qemu_monitor_json.c | 1 + .../caps_4.2.0.aarch64.xml | 1 + .../caps_4.2.0.x86_64.xml | 1 + .../net-virtio-teaming-network.xml | 37 +++++++ .../qemuxml2argvdata/net-virtio-teaming.args | 40 +++++++ tests/qemuxml2argvdata/net-virtio-teaming.xml | 50 +++++++++ tests/qemuxml2argvtest.c | 4 + .../net-virtio-teaming-network.xml | 51 +++++++++ .../qemuxml2xmloutdata/net-virtio-teaming.xml | 66 ++++++++++++ tests/qemuxml2xmltest.c | 6 ++ 22 files changed, 563 insertions(+), 7 deletions(-) create mode 100644 tests/qemuxml2argvdata/net-virtio-teaming-network.xml create mode 100644 tests/qemuxml2argvdata/net-virtio-teaming.args create mode 100644 tests/qemuxml2argvdata/net-virtio-teaming.xml create mode 100644 tests/qemuxml2xmloutdata/net-virtio-teaming-network.xml create mode 100644 tests/qemuxml2xmloutdata/net-virtio-teaming.xml -- 2.24.1
