On Fri, Oct 25, 2019 at 02:19:19PM +0200, Jens Freimann wrote: > This is implementing the host side of the net_failover concept > (https://www.kernel.org/doc/html/latest/networking/net_failover.html)
OK so I put this on a next branch for now, to merge after the release. I plan to rebase it after rc1, and then stop rebasing. > Changes since v5: > * rename net_failover_pair_id parameter/property to failover_pair_id > * in PCI code use pci_bus_is_express(). This won't fail on functions > 0 > * make sure primary and standby can't be added to same PCI slot > * add documentation file in docs/ to virtio-net patch, add file to > MAINTAINERS (added to networking devices section) > * add comment to QAPI event for failover negotiation, try to improve > commit message > > The general idea is that we have a pair of devices, a vfio-pci and a > virtio-net device. Before migration the vfio device is unplugged and data > flows to the virtio-net device, on the target side another vfio-pci device > is plugged in to take over the data-path. In the guest the net_failover > module will pair net devices with the same MAC address. > > * Patch 1 adds the infrastructure to hide the device for the qbus and qdev > APIs > > * Patch 2 adds checks to PCIDevice for only allowing ethernet devices as > failover primary and only PCIExpress capable devices > > * Patch 3 sets a new flag for PCIDevice 'partially_hotplugged' which we > use to skip the unrealize code path when doing a unplug of the primary > device > > * Patch 4 sets the pending_deleted_event before triggering the guest > unplug request > > * Patch 5 and 6 add new qmp events, one sends the device id of a device > that was just requested to be unplugged from the guest and another one > to let libvirt know if VIRTIO_NET_F_STANDBY was negotiated > > * Patch 7 make sure that we can unplug the vfio-device before > migration starts > > * Patch 8 adds a new migration state that is entered while we wait for > devices to be unplugged by guest OS > > * Patch 9 just adds the new migration state to a check in libqos code > > * Patch 10 In the second patch the virtio-net uses the API to defer adding > the vfio > device until the VIRTIO_NET_F_STANDBY feature is acked. It also > implements the migration handler to unplug the device from the guest and > re-plug in case of migration failure > > * Patch 11 allows migration for failover vfio-pci devices > > Previous discussion: > RFC v1 https://patchwork.ozlabs.org/cover/989098/ > RFC v2 https://www.mail-archive.com/qemu-devel@nongnu.org/msg606906.html > v1: https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg03968.html > v2: https://www.mail-archive.com/qemu-devel@nongnu.org/msg635214.html > v3: https://patchew.org/QEMU/20191011112015.11785-1-jfreim...@redhat.com/ > v4: https://patchew.org/QEMU/20191018202040.30349-1-jfreim...@redhat.com/ > v5: https://patchew.org/QEMU/20191023082711.16694-1-jfreim...@redhat.com/ > > To summarize concerns/feedback from previous discussion: > 1.- guest OS can reject or worse _delay_ unplug by any amount of time. > Migration might get stuck for unpredictable time with unclear reason. > This approach combines two tricky things, hot/unplug and migration. > -> We need to let libvirt know what's happening. Add new qmp events > and a new migration state. When a primary device is (partially) > unplugged (only from guest) we send a qmp event with the device id. When > it is unplugged from the guest the DEVICE_DELETED event is sent. > Migration will enter the wait-unplug state while waiting for the guest > os to unplug all primary devices and then move on with migration. > 2. PCI devices are a precious ressource. The primary device should never > be added to QEMU if it won't be used by guest instead of hiding it in > QEMU. > -> We only hotplug the device when the standby feature bit was > negotiated. We save the device cmdline options until we need it for > qdev_device_add() > Hiding a device can be a useful concept to model. For example a > pci device in a powered-off slot could be marked as hidden until the > slot is > powered on (mst). > 3. Management layer software should handle this. Open Stack already has > components/code to handle unplug/replug VFIO devices and metadata to > provide to the guest for detecting which devices should be paired. > -> An approach that includes all software from firmware to > higher-level management software wasn't tried in the last years. This is > an attempt to keep it simple and contained in QEMU as much as possible. > One of the problems that stopped management software and libvirt from > implementing this idea is that it can't be sure that it's possible to > re-plug the primary device. By not freeing the devices resources in QEMU > and only asking the guest OS to unplug it is possible to re-plug the > device in case of a migration failure. > 4. Hotplugging a device and then making it part of a failover setup is > not possible > -> addressed by extending qdev hotplug functions to check for hidden > attribute, so e.g. device_add can be used to plug a device. > > > I have tested this with a mlx5 and igb NIC and was able to migrate the VM. > > Command line example: > > qemu-system-x86_64 -enable-kvm -m 3072 -smp 3 \ > -machine q35,kernel-irqchip=split -cpu host \ > -serial stdio \ > -net none \ > -qmp unix:/tmp/qmp.socket,server,nowait \ > -monitor telnet:127.0.0.1:5555,server,nowait \ > -device pcie-root-port,id=root0,multifunction=on,chassis=0,addr=0xa \ > -device pcie-root-port,id=root1,bus=pcie.0,chassis=1 \ > -device pcie-root-port,id=root2,bus=pcie.0,chassis=2 \ > -netdev > tap,script=/root/bin/bridge.sh,downscript=no,id=hostnet1,vhost=on \ > -device > virtio-net-pci,netdev=hostnet1,id=net1,mac=52:54:00:6f:55:cc,bus=root2,failover=on > \ > -device vfio-pci,host=5e:00.2,id=hostdev0,bus=root1,failover_pair_id > =net1 \ > /root/rhel-guest-image-8.0-1781.x86_64.qcow2 > > I'm grateful for any remarks or ideas! > > Thanks! > > regards, > Jens > > > Jens Freimann (11): > qdev/qbus: add hidden device support > pci: add option for net failover > pci: mark devices partially unplugged > pci: mark device having guest unplug request pending > qapi: add unplug primary event > qapi: add failover negotiated event > migration: allow unplug during migration for failover devices > migration: add new migration state wait-unplug > libqos: tolerate wait-unplug migration state > net/virtio: add failover support > vfio: unplug failover primary device before migration > > MAINTAINERS | 1 + > docs/virtio-net-failover.rst | 68 ++++++++ > hw/core/qdev.c | 25 +++ > hw/net/virtio-net.c | 302 +++++++++++++++++++++++++++++++++ > hw/pci/pci.c | 32 ++++ > hw/pci/pcie.c | 6 + > hw/vfio/pci.c | 26 ++- > hw/vfio/pci.h | 1 + > include/hw/pci/pci.h | 4 + > include/hw/qdev-core.h | 30 ++++ > include/hw/virtio/virtio-net.h | 12 ++ > include/hw/virtio/virtio.h | 1 + > include/migration/vmstate.h | 2 + > migration/migration.c | 21 +++ > migration/migration.h | 3 + > migration/savevm.c | 36 ++++ > migration/savevm.h | 2 + > qapi/migration.json | 24 ++- > qapi/net.json | 19 +++ > qdev-monitor.c | 43 ++++- > tests/libqos/libqos.c | 3 +- > vl.c | 6 +- > 22 files changed, 652 insertions(+), 15 deletions(-) > create mode 100644 docs/virtio-net-failover.rst > > -- > 2.21.0
