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Re: [PATCH v3 0/10] add failover feature for assigned network devices
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH v3 0/10] add failover feature for assigned network devices |
Date: |
Fri, 11 Oct 2019 10:28:58 -0400 |
On Fri, Oct 11, 2019 at 01:20:05PM +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)
I posted a comment about the migration changes.
Besides that this looks good to me.
I did not look at VFIO parts at all yet.
Alex, could you pls review/ack the VFIO patch?
> Changes since v2:
> * back out of creating failover pair when it is a non-networking
> vfio-pci device (Alex W)
> * handle migration state change from within the migration thread. I do a
> timed wait on a semaphore and then check if all unplugs were
> succesful. Added a new function to each device that checks the device
> if the unplug for it has happened. When all devices report the succesful
> unplug *or* the time/retries is up, continue with the migration or
> cancel. When not all devices could be unplugged I am cancelling at the
> moment. It is likely that we can't plug it back at the destination which
> would result in degraded network performance.
> * fix a few bugs regarding re-plug on migration source and target
> * run full set of tests including migration tests
> * add patch for libqos to tolerate new migration state
> * squashed patch 1 and 2, added patch 8
>
> 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 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 3 sets the pending_deleted_event before triggering the guest
> unplug request
>
> * Patch 4 and 5 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 6 make sure that we can unplug the vfio-device before
> migration starts
>
> * Patch 7 adds a new migration state that is entered while we wait for
> devices to be unplugged by guest OS
>
> * Patch 8 just adds the new migration state to a check in libqos code
>
> * Patch 9 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 10 allows migration for failover vfio-pci devices, but only when it is
> a networking device
>
> Previous discussion:
> RFC v1 https://patchwork.ozlabs.org/cover/989098/
> RFC v2 https://www.mail-archive.com/address@hidden/msg606906.html
> v1: https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg03968.html
> v2: https://www.mail-archive.com/address@hidden/msg635214.html
>
> 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,net_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 (10):
> qdev/qbus: add hidden device support
> 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
>
> hw/core/qdev.c | 20 +++
> hw/net/virtio-net.c | 267 +++++++++++++++++++++++++++++++++
> hw/pci/pci.c | 2 +
> hw/pci/pcie.c | 6 +
> hw/vfio/pci.c | 35 ++++-
> hw/vfio/pci.h | 2 +
> include/hw/pci/pci.h | 1 +
> include/hw/qdev-core.h | 10 ++
> include/hw/virtio/virtio-net.h | 12 ++
> include/hw/virtio/virtio.h | 1 +
> include/migration/vmstate.h | 2 +
> migration/migration.c | 34 +++++
> migration/migration.h | 3 +
> migration/savevm.c | 36 +++++
> migration/savevm.h | 1 +
> qapi/migration.json | 24 ++-
> qapi/net.json | 16 ++
> qdev-monitor.c | 43 +++++-
> tests/libqos/libqos.c | 3 +-
> vl.c | 6 +-
> 20 files changed, 515 insertions(+), 9 deletions(-)
>
> --
> 2.21.0
- Re: [PATCH v3 07/10] migration: add new migration state wait-unplug, (continued)
[PATCH v3 08/10] libqos: tolerate wait-unplug migration state, Jens Freimann, 2019/10/11
[PATCH v3 09/10] net/virtio: add failover support, Jens Freimann, 2019/10/11
[PATCH v3 10/10] vfio: unplug failover primary device before migration, Jens Freimann, 2019/10/11
Re: [PATCH v3 0/10] add failover feature for assigned network devices,
Michael S. Tsirkin <=
Re: [PATCH v3 0/10] add failover feature for assigned network devices, no-reply, 2019/10/11
Re: [PATCH v3 0/10] add failover feature for assigned network devices, Alex Williamson, 2019/10/15