Re: [pve-devel] [PATCH qemu-server 4/4] cpu config: Unify the default value for 'kvm'

[Filip Schauer <f.schauer@proxmox.com>]

On 19/02/2024 15:47, Fiona Ebner wrote:
> On an x86_64 host, for guests using a different architecture (i.e.
> aarch64), hot-plugging is already broken, because we try to hotplug a
> CPU of type "$cpu-x86_64-cpu,XYZ" which won't work anyways:
>
> vcpus: hotplug problem - VM 130 qmp command 'device_add' failed -
> 'kvm64-x86_64-cpu' is not a valid device model name
>
> The actual breaking change is for the host arch being something other
> than x86_64 (which isn't officially supported) and the VM being x86_64, ...
>
>> @@ -414,9 +415,9 @@ sub get_custom_model {
>>   
>>   # Print a QEMU device node for a given VM configuration for hotplugging CPUs
>>   sub print_cpu_device {
>> -    my ($conf, $id) = @_;
>> +    my ($conf, $arch, $id) = @_;
>>   
>> -    my $kvm = $conf->{kvm} // 1;
>> +    my $kvm = $conf->{kvm} // is_native($arch);
>>       my $cpu = get_default_cpu_type('x86_64', $kvm);
> ...because in that case, before this patch we got kvm64 here, but with
> the patch we get qemu64 which would be a problem for live-migration.

I expressed my opinion on this matter in the following mail:

https://lists.proxmox.com/pipermail/pve-devel/2023-December/061131.html