Re: [pve-devel] [PATCH qemu-server v2 2/4] api: vm start: introduce nets-host-mtu parameter for migration compat

[Fiona Ebner <f.ebner@proxmox.com>]

Am 04.09.25 um 11:28 AM schrieb Fiona Ebner:
> Am 04.09.25 um 11:11 AM schrieb Fabian Grünbichler:
>> On September 3, 2025 4:22 pm, Fiona Ebner wrote:
>>> @@ -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
>>
>> can this happen in practice (without manually editing the config or
>> manual QMP commands)?
> 
> I don't think so. But since we have the info, I though it'd be good to
> warn about it.
> 
>>
>>> +            } 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";
>>> +        }
>>> +    }
>>
>> this if here

Oh, I suppose you mean the 'if' further above, not the one right below?
I had that at first, but decided to split out printing the messages to
avoid cluttering the code below.

>>
>>> +
>>> +    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) {
>>
>> and this if here could be combined?
> 
> How? You mean setting $mtu = $host_mtu_migration; early if there is a
> non-zero value?


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