From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id CBE1F1FF189 for ; Thu, 4 Sep 2025 20:11:46 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 0647535D2A; Thu, 4 Sep 2025 20:12:00 +0200 (CEST) Message-ID: Date: Thu, 4 Sep 2025 20:11:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta To: Proxmox VE development discussion , Fiona Ebner References: <20250904124113.81772-1-f.ebner@proxmox.com> <20250904124113.81772-9-f.ebner@proxmox.com> Content-Language: en-US From: Thomas Lamprecht In-Reply-To: <20250904124113.81772-9-f.ebner@proxmox.com> X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1757009498494 X-SPAM-LEVEL: Spam detection results: 0 AWL -0.030 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 RCVD_IN_VALIDITY_CERTIFIED_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. 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SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: Re: [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" Am 04.09.25 um 14:42 schrieb Fiona Ebner: > 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. Which breaks migration from new to old, which can be fine, but seems avoidable given that we got a tunnel that we can query stuff over. Maybe we could at least catch the "Unknown option: nets-host-mtu" error explicitly and add some context that the target likely just needs to be updated to make the migration work. > > [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"); _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel