[pve-devel] [PATCH-SERIES qemu-server v2 0/4] virtio-net: fix migration between default/non-default MTUs, part one and two

[Fiona Ebner]

Changes in v2:
* push make tidy change already to master
* add part two - migration
* move version_guard() call to outside of print_netdevice_full() call
* add comment about why host_mtu is always set in source code

The virtual hardware is generated differently (at least for i440fx
machines) when host_mtu is set or not set on the netdev command line
[0]. When the MTU is the same value as the default 1500, Proxmox VE
did not add a host_mtu parameter. This is problematic for migration
where host_mtu is present on one end of the migration, but not on the
other [1].

Always set the host_mtu parameter starting with machine version
10.0+pve1 to avoid this issue going forward. For snapshots, the
nets-host-mtu information needs to be recorded in the snapshot config.
When the information is not present, and the machine version is
10.0+pve0, the Proxmox VE 9 behavior can be used. For other machine
versions we need to decide whether to use Proxmox VE 8 or Proxmox VE 9
behavior. The VM start parameter already provides an escape hatch in
any case. This will be the third an final part of these series.

Moreover, the effective setting in the guest (state) will
still be the host_mtu from the source side, even if a different value
is used for host_mtu on the target instance's commandline. This will
not lead to an error loading the migration stream in QEMU, but having
a larger host_mtu than the bridge MTU is still problematic for certain
network traffic like
> iperf3 -c 10.10.10.11 -u -l 2k
when host_mtu=9000 and bridge MTU=1500.

Add the necessary parameter for VM start and pass the values along for
migration to preserve the values going forward.

For Proxmox VE 8, add a dummy setting for VM start and also start
passing along the values.


Fiona Ebner (3):
  virtio-net: fix migration between default/non-default MTUs starting
    with machine version 10.0+pve1
  api: vm start: introduce nets-host-mtu parameter for migration compat
  migration: preserve host_mtu for virtio-net devices


stable-bookworm:

Fiona Ebner (1):
  migration: preserve host_mtu for virtio-net devices

 src/PVE/API2/Qemu.pm                          | 11 +++
 src/PVE/QemuMigrate.pm                        | 37 ++++++++++
 src/PVE/QemuServer.pm                         | 69 +++++++++++++++++--
 src/PVE/QemuServer/Machine.pm                 |  6 ++
 src/test/MigrationTest/QemuMigrateMock.pm     |  9 +++
 src/test/cfg2cmd/bootorder-empty.conf.cmd     |  4 +-
 src/test/cfg2cmd/bootorder-legacy.conf.cmd    |  4 +-
 src/test/cfg2cmd/bootorder.conf.cmd           |  4 +-
 src/test/cfg2cmd/efidisk-on-rbd.conf.cmd      |  4 +-
 src/test/cfg2cmd/ide.conf.cmd                 |  4 +-
 .../cfg2cmd/netdev-7.1-multiqueues.conf.cmd   |  2 +-
 src/test/cfg2cmd/netdev-7.1.conf.cmd          |  2 +-
 src/test/cfg2cmd/netdev_vxlan.conf.cmd        |  2 +-
 src/test/cfg2cmd/q35-ide.conf.cmd             |  4 +-
 .../q35-linux-hostpci-mapping.conf.cmd        |  4 +-
 .../q35-linux-hostpci-multifunction.conf.cmd  |  4 +-
 ...q35-linux-hostpci-x-pci-overrides.conf.cmd |  4 +-
 src/test/cfg2cmd/q35-linux-hostpci.conf.cmd   |  4 +-
 src/test/cfg2cmd/q35-simple.conf.cmd          |  4 +-
 src/test/cfg2cmd/seabios_serial.conf.cmd      |  4 +-
 src/test/cfg2cmd/simple-btrfs.conf.cmd        |  4 +-
 .../cfg2cmd/simple-disk-passthrough.conf.cmd  |  4 +-
 src/test/cfg2cmd/simple-rbd.conf.cmd          |  4 +-
 src/test/cfg2cmd/simple-virtio-blk.conf.cmd   |  4 +-
 .../cfg2cmd/simple-zfs-over-iscsi.conf.cmd    |  4 +-
 src/test/cfg2cmd/simple1.conf.cmd             |  4 +-
 26 files changed, 165 insertions(+), 45 deletions(-)

-- 
2.47.2