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 AA75D1FF189 for ; Thu, 4 Sep 2025 14:42:02 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id C1BC72EA98; Thu, 4 Sep 2025 14:41:56 +0200 (CEST) From: Fiona Ebner To: pve-devel@lists.proxmox.com Date: Thu, 4 Sep 2025 14:40:52 +0200 Message-ID: <20250904124113.81772-9-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: 1756989664331 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 stable-bookworm 8/8] 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: * Adapt to moved/changed get_nets_host_mtu() helper. The Network module does not exist yet in PVE 8, and parse_net() lives in QemuServer itself, so the helper is also moved there. src/PVE/QemuMigrate.pm | 8 +++++++ src/PVE/QemuServer.pm | 27 +++++++++++++++++++++++ src/test/MigrationTest/QemuMigrateMock.pm | 15 +++++++++++++ 3 files changed, 50 insertions(+) diff --git a/src/PVE/QemuMigrate.pm b/src/PVE/QemuMigrate.pm index 28d7ac56..3cd7069a 100644 --- a/src/PVE/QemuMigrate.pm +++ b/src/PVE/QemuMigrate.pm @@ -959,6 +959,10 @@ 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'); } @@ -1144,6 +1148,10 @@ sub phase2 { }, }; + if (my $nets_host_mtu = PVE::QemuServer::get_nets_host_mtu($vmid, $conf)) { + $params->{start_params}->{'nets-host-mtu'} = $nets_host_mtu; + } + my ($tunnel_info, $spice_port); my @online_local_volumes = $self->filter_local_volumes('online'); diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm index 47c96726..5b08b3e3 100644 --- a/src/PVE/QemuServer.pm +++ b/src/PVE/QemuServer.pm @@ -9533,4 +9533,31 @@ sub delete_ifaces_ipams_ips { } } +sub get_nets_host_mtu { + my ($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 f678f9ec..05b2c5c1 100644 --- a/src/test/MigrationTest/QemuMigrateMock.pm +++ b/src/test/MigrationTest/QemuMigrateMock.pm @@ -175,6 +175,21 @@ $MigrationTest::Shared::qemu_server_module->mock( delete $expected_calls->{'vm_stop'}; }, del_nets_bridge_fdb => sub { return; }, + mon_cmd => sub { + my ($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_cpuconfig_module = Test::MockModule->new("PVE::QemuServer::CPUConfig"); -- 2.39.5 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel