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]. 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. Preventing migrations in this case would be a breaking change, so for now, only a warning is added.
Add the necessary parameter for VM start to allow preserving the values going forward. [0]: https://bugzilla.redhat.com/show_bug.cgi?id=1449346 [1]: https://forum.proxmox.com/threads/live-vm-migration-fails.169537/post-796379 Signed-off-by: Fiona Ebner <f.eb...@proxmox.com> --- src/PVE/API2/Qemu.pm | 11 ++++++++ src/PVE/QemuServer.pm | 61 ++++++++++++++++++++++++++++++++++++++----- 2 files changed, 66 insertions(+), 6 deletions(-) diff --git a/src/PVE/API2/Qemu.pm b/src/PVE/API2/Qemu.pm index b571e6c1..95db271b 100644 --- a/src/PVE/API2/Qemu.pm +++ b/src/PVE/API2/Qemu.pm @@ -3383,6 +3383,15 @@ __PACKAGE__->register_method({ default => 0, description => 'Whether to migrate conntrack entries for running VMs.', }, + 'nets-host-mtu' => { + type => 'string', + pattern => 'net\d+=\d+(,net\d+=\d+)*', + optional => 1, + description => + 'Used for migration compat. List of VirtIO network devices and their effective' + . ' host_mtu setting according to the QEMU object model on the source side of' + . ' the migration.', + }, }, }, returns => { @@ -3414,6 +3423,7 @@ __PACKAGE__->register_method({ my $targetstorage = $get_root_param->('targetstorage'); my $force_cpu = $get_root_param->('force-cpu'); my $with_conntrack_state = $get_root_param->('with-conntrack-state'); + my $nets_host_mtu = $get_root_param->('nets-host-mtu'); my $storagemap; @@ -3501,6 +3511,7 @@ __PACKAGE__->register_method({ forcemachine => $machine, timeout => $timeout, forcecpu => $force_cpu, + 'nets-host-mtu' => $nets_host_mtu, }; PVE::QemuServer::vm_start($storecfg, $vmid, $params, $migrate_opts); diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm index 5b7087dc..77b8e9c4 100644 --- a/src/PVE/QemuServer.pm +++ b/src/PVE/QemuServer.pm @@ -1457,7 +1457,17 @@ sub print_pbs_blockdev { } sub print_netdevice_full { - my ($vmid, $conf, $net, $netid, $bridges, $use_old_bios_files, $arch, $machine_version) = @_; + my ( + $vmid, + $conf, + $net, + $netid, + $bridges, + $use_old_bios_files, + $arch, + $machine_version, + $host_mtu_migration, # force this value for host_mtu, 0 means force absence of param + ) = @_; my $device = $net->{model}; if ($net->{model} eq 'virtio') { @@ -1484,10 +1494,37 @@ sub print_netdevice_full { my $mtu = $net->{mtu}; - if ($net->{model} eq 'virtio' && $net->{bridge}) { + if (defined($host_mtu_migration)) { + if ($host_mtu_migration) { + if (defined($mtu) && $mtu != 1) { + if ($mtu != $host_mtu_migration) { + log_warn( + "netdev $netid: using 'host_mtu=$host_mtu_migration' for migration compat," + . " but value different from value in configuration '$mtu'"); + } # else avoid being overly verbose if there is an explicit setting + } else { + print "netdev $netid: using 'host_mtu=$host_mtu_migration' for migration compat\n"; + } + } else { + print "netdev $netid: not adding 'host_mtu' parameter for migration compat\n"; + } + } + + if ( + $net->{model} eq 'virtio' + && $net->{bridge} + && (!defined($host_mtu_migration) || $host_mtu_migration) + ) { my $bridge_mtu = PVE::Network::read_bridge_mtu($net->{bridge}); - if (!defined($mtu) || $mtu == 1) { + if ($host_mtu_migration) { + $mtu = $host_mtu_migration; + # TODO PVE 10 - upgrade to failure? Certain network traffic can break like + # iperf3 -c 10.10.10.11 -u -l 2k when host_mtu=9000 and bridge MTU=1500 + if ($mtu > $bridge_mtu) { + log_warn("netdev $netid: MTU '$mtu' is bigger than the bridge MTU '$bridge_mtu'"); + } + } elsif (!defined($mtu) || $mtu == 1) { $mtu = $bridge_mtu; } elsif ($mtu < 576) { die "netdev $netid: MTU '$mtu' is smaller than the IP minimum MTU '576'\n"; @@ -1495,7 +1532,7 @@ sub print_netdevice_full { die "netdev $netid: MTU '$mtu' is bigger than the bridge MTU '$bridge_mtu'\n"; } - if (min_version($machine_version, 10, 0, 1)) { + if (min_version($machine_version, 10, 0, 1) || $host_mtu_migration) { # Always add host_mtu for migration compatibility, because the presence of host_mtu # means that the virtual hardware is generated differently (at least for i440fx) $tmpstr .= ",host_mtu=$mtu"; @@ -1503,8 +1540,14 @@ sub print_netdevice_full { $tmpstr .= ",host_mtu=$mtu" if $mtu != 1500; } } elsif (defined($mtu)) { - warn - "WARN: netdev $netid: ignoring MTU '$mtu', not using VirtIO or no bridge configured.\n"; + my $msg_prefix = "netdev $netid: ignoring MTU '$mtu'"; + if (defined($host_mtu_migration) && !$host_mtu_migration) { + log_warn("$msg_prefix, not used on the source side according to migration parameters"); + } elsif (!$net->{bridge}) { + log_warn("$msg_prefix, no bridge configured"); + } else { + log_warn("$msg_prefix, not using VirtIO"); + } } if ($use_old_bios_files) { @@ -3810,6 +3853,8 @@ sub config_to_command { }, ); + my $nets_host_mtu = + { map { split('=', $_) } PVE::Tools::split_list($options->{'nets-host-mtu'}) }; for (my $i = 0; $i < $MAX_NETS; $i++) { my $netname = "net$i"; @@ -3836,6 +3881,7 @@ sub config_to_command { $use_old_bios_files, $arch, $machine_version, + $nets_host_mtu->{$netname}, ); push @$devices, '-device', $netdevicefull; @@ -5566,6 +5612,8 @@ sub vm_start { # }, # virtio2 => ... # } +# nets-host-mtu => Used for migration compat. List of VirtIO network devices and their effective +# host_mtu setting according to the QEMU object model on the source side of the migration. # migrate_opts: # nbd => volumes for NBD exports (vm_migrate_alloc_nbd_disks) # migratedfrom => source node @@ -5678,6 +5726,7 @@ sub vm_start_nolock { 'force-machine' => $forcemachine, 'force-cpu' => $forcecpu, 'live-restore-backing' => $params->{'live-restore-backing'}, + 'nets-host-mtu' => $params->{'nets-host-mtu'}, }, ); -- 2.47.2 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
