From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) by lore.proxmox.com (Postfix) with ESMTPS id 3F4161FF189 for ; Thu, 4 Sep 2025 14:41:11 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 1BEB82E81F; Thu, 4 Sep 2025 14:41:25 +0200 (CEST) From: Fiona Ebner To: pve-devel@lists.proxmox.com Date: Thu, 4 Sep 2025 14:40:47 +0200 Message-ID: <20250904124113.81772-4-f.ebner@proxmox.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250904124113.81772-1-f.ebner@proxmox.com> References: <20250904124113.81772-1-f.ebner@proxmox.com> MIME-Version: 1.0 X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1756989664221 X-SPAM-LEVEL: Spam detection results: 0 AWL -0.023 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: [pve-devel] [PATCH qemu-server v3 3/8] migration: preserve host_mtu for virtio-net devices X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Proxmox VE development discussion Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: pve-devel-bounces@lists.proxmox.com Sender: "pve-devel" 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 --- Changes in v3: * move get_nets_host_mtu to network module * avoid overly long line in tests src/PVE/QemuMigrate.pm | 8 +++++++ src/PVE/QemuServer/Network.pm | 29 +++++++++++++++++++++++ src/test/MigrationTest/QemuMigrateMock.pm | 15 ++++++++++++ 3 files changed, 52 insertions(+) diff --git a/src/PVE/QemuMigrate.pm b/src/PVE/QemuMigrate.pm index e18cc2aa..4381b542 100644 --- a/src/PVE/QemuMigrate.pm +++ b/src/PVE/QemuMigrate.pm @@ -998,6 +998,10 @@ 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 +1191,10 @@ sub phase2 { }, }; + if (my $nets_host_mtu = PVE::QemuServer::Network::get_nets_host_mtu($vmid, $conf)) { + $params->{start_params}->{'nets-host-mtu'} = $nets_host_mtu; + } + my ($tunnel_info, $spice_port); my @online_local_volumes = $self->filter_local_volumes('online'); diff --git a/src/PVE/QemuServer/Network.pm b/src/PVE/QemuServer/Network.pm index 56df83fb..eb8222e8 100644 --- a/src/PVE/QemuServer/Network.pm +++ b/src/PVE/QemuServer/Network.pm @@ -11,6 +11,8 @@ use PVE::Network::SDN::Zones; use PVE::RESTEnvironment qw(log_warn); use PVE::Tools qw($IPV6RE file_read_firstline); +use PVE::QemuServer::Monitor qw(mon_cmd); + my $nic_model_list = [ 'e1000', 'e1000-82540em', @@ -330,4 +332,31 @@ sub tap_plug { PVE::Network::SDN::Zones::tap_plug($iface, $bridge, $tag, $firewall, $trunks, $rate); } +sub get_nets_host_mtu { + my ($vmid, $conf) = @_; + + my $nets_host_mtu = []; + for my $opt (sort keys $conf->%*) { + next if $opt !~ m/^net(\d+)$/; + my $net = parse_net($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 = $@) { + log_warn("$opt: could not query host_mtu - $err"); + } elsif (defined($host_mtu)) { + push $nets_host_mtu->@*, "${opt}=${host_mtu}"; + } else { + log_warn("$opt: got undefined value when querying host_mtu"); + } + } + return join(',', $nets_host_mtu->@*); +} + 1; diff --git a/src/test/MigrationTest/QemuMigrateMock.pm b/src/test/MigrationTest/QemuMigrateMock.pm index b04cf78b..421f0bb7 100644 --- a/src/test/MigrationTest/QemuMigrateMock.pm +++ b/src/test/MigrationTest/QemuMigrateMock.pm @@ -225,6 +225,21 @@ $qemu_server_machine_module->mock( my $qemu_server_network_module = Test::MockModule->new("PVE::QemuServer::Network"); $qemu_server_network_module->mock( del_nets_bridge_fdb => sub { return; }, + mon_cmd => sub { + my ($vmid, $command, %params) = @_; + + if ($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"; + }, ); my $qemu_server_qmphelpers_module = Test::MockModule->new("PVE::QemuServer::QMPHelpers"); -- 2.47.2 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel