https://bugzilla.redhat.com/1693587 'QEMU 4.2.0 and later, combined with a sufficiently recent guest virtio-net driver, supports setting up a simple network bond device comprised of one virtio emulated NIC and one hostdev NIC (which must be an SRIOV VF). The allure of this setup is that the bond will always favor the hostdev device, providing better performance, until the guest is migrated - at that time QEMU will automatically unplug the hostdev NIC and the bond will send all traffic via the virtio NIC until migration is completed, then QEMU on the destination side will hotplug a new hostdev NIC and the bond will switch back to using the hostdev for network traffic. The result is that guests desiring the extra performance of a hostdev NIC are now migratable without network downtime (performance is just degraded during migration) and without requiring a complicated bonding configuration in the guest OS network config and complicated unplug/replug logic in the management application on the host - it can instead all be accomplished in libvirt with the interface <driver> subelement "failover" and "backupAlias" attributes. Patches 1-4 are just simple refactoring with no functional change, 5-10 are the new functionality, patch 11 is documentation, and Patch 12 is an RFC for a method to solve a problem that oVirt has when trying to use this feature - while the virtio guest driver requires the pair of interfaces to have matching MAC addresses, oVirt requires every network interface to have a unique MAC. I'm not sure that I like having this hackishness in libvirt (see the commit log message), but it does solve oVirt's problem, and also makes direct config with libvirt XML simpler (since it removes the need to manually specify any MAC addresses in order to arrive at a working config, which is something that has always been the case before now). I'll leave it up to the jury to decide whether or not it's acceptable :-) Laine Stump (12): conf: refactor hostdev driver subelement format for simpler additions conf: change virDomainVirtioNet*Format() to return void conf: rename two static functions conf: refactor <interface>'s <driver> subelement parse/format qemu: add capabilities flag for failover feature conf: add failover attribute to <driver> subelement of <interface> qemu: add backupAlias attribute to <driver> subelement of hostdev devices conf: add backupAlias attribute to <interface> driver subelement qemu: allow migration with assigned PCI hostdev if backupAlias is set qemu: add wait-unplug to qemu migration status enum docs: document virtio failover / QEMU auto-plug of hostdev during migration conf/qemu: new <driver> attribute "useBackupMAC" docs/formatdomain.html.in | 74 +++ docs/news.xml | 27 + docs/schemas/domaincommon.rng | 15 + src/conf/domain_conf.c | 559 ++++++++++-------- src/conf/domain_conf.h | 57 +- src/libxl/libxl_driver.c | 2 +- src/qemu/qemu_capabilities.c | 2 + src/qemu/qemu_capabilities.h | 1 + src/qemu/qemu_command.c | 5 + src/qemu/qemu_domain.c | 21 +- src/qemu/qemu_hostdev.c | 5 +- src/qemu/qemu_hostdev.h | 1 + src/qemu/qemu_hotplug.c | 2 +- src/qemu/qemu_migration.c | 49 +- src/qemu/qemu_monitor.c | 1 + src/qemu/qemu_monitor.h | 1 + src/qemu/qemu_monitor_json.c | 1 + src/util/virhostdev.c | 47 +- src/util/virhostdev.h | 1 + .../caps_4.2.0.aarch64.xml | 1 + .../caps_4.2.0.x86_64.xml | 1 + .../net-virtio-failover-network.xml | 37 ++ .../qemuxml2argvdata/net-virtio-failover.args | 40 ++ .../qemuxml2argvdata/net-virtio-failover.xml | 50 ++ tests/qemuxml2argvtest.c | 4 + .../net-virtio-failover-network.xml | 51 ++ .../net-virtio-failover.xml | 66 +++ tests/qemuxml2xmltest.c | 6 + tests/virhostdevtest.c | 18 +- 29 files changed, 856 insertions(+), 289 deletions(-) create mode 100644 tests/qemuxml2argvdata/net-virtio-failover-network.xml create mode 100644 tests/qemuxml2argvdata/net-virtio-failover.args create mode 100644 tests/qemuxml2argvdata/net-virtio-failover.xml create mode 100644 tests/qemuxml2xmloutdata/net-virtio-failover-network.xml create mode 100644 tests/qemuxml2xmloutdata/net-virtio-failover.xml -- 2.24.1
