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.
Pass the values from the source to the target during migration to be able to preserve them. [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/QemuMigrate.pm | 37 +++++++++++++++++++++++ src/test/MigrationTest/QemuMigrateMock.pm | 9 ++++++ 2 files changed, 46 insertions(+) diff --git a/src/PVE/QemuMigrate.pm b/src/PVE/QemuMigrate.pm index e18cc2aa..a43bd615 100644 --- a/src/PVE/QemuMigrate.pm +++ b/src/PVE/QemuMigrate.pm @@ -175,6 +175,35 @@ sub target_storage_check_available { } } +my sub get_nets_host_mtu { + my ($self, $vmid) = @_; + + my $conf = $self->{vmconf}; + + my $nets_host_mtu = []; + for my $opt (sort keys $conf->%*) { + next if $opt !~ m/^net(\d+)$/; + my $net = PVE::QemuServer::Network::parse_net($conf->{$opt}); + next if $net->{model} ne 'virtio'; + + my $host_mtu = eval { + mon_cmd( + $vmid, 'qom-get', + path => "/machine/peripheral/$opt", + property => 'host_mtu', + ); + }; + if (my $err = $@) { + $self->log('warn', "$opt: could not query host_mtu - $err"); + } elsif (defined($host_mtu)) { + push $nets_host_mtu->@*, "${opt}=${host_mtu}"; + } else { + $self->log('warn', "$opt: got undefined value when querying host_mtu"); + } + } + return join(',', $nets_host_mtu->@*); +} + sub prepare { my ($self, $vmid) = @_; @@ -998,6 +1027,10 @@ sub phase2_start_local_cluster { push @$cmd, '--force-cpu', $start->{forcecpu}; } + if ($start->{'nets-host-mtu'}) { + push @$cmd, '--nets-host-mtu', $start->{'nets-host-mtu'}; + } + if ($self->{storage_migration}) { push @$cmd, '--targetstorage', ($self->{opts}->{targetstorage} // '1'); } @@ -1187,6 +1220,10 @@ sub phase2 { }, }; + if (my $nets_host_mtu = get_nets_host_mtu($self, $vmid)) { + $params->{start_params}->{'nets-host-mtu'} = $nets_host_mtu; + } + my ($tunnel_info, $spice_port); my @online_local_volumes = $self->filter_local_volumes('online'); diff --git a/src/test/MigrationTest/QemuMigrateMock.pm b/src/test/MigrationTest/QemuMigrateMock.pm index b04cf78b..ca88d758 100644 --- a/src/test/MigrationTest/QemuMigrateMock.pm +++ b/src/test/MigrationTest/QemuMigrateMock.pm @@ -112,6 +112,15 @@ $qemu_migrate_module->mock( return; } elsif ($command eq 'migrate_cancel') { return; + } elsif ($command eq 'qom-get') { + if ( + $params{path} =~ m|^/machine/peripheral/net\d+$| + && $params{property} eq 'host_mtu' + ) { + return 1500; + } + die + "mon_cmd (mocked) - implement me: $command for path '$params{path}' property '$params{property}'"; } die "mon_cmd (mocked) - implement me: $command"; }, -- 2.47.2 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
