Re: [pve-devel] [PATCH qemu-server 3/3] fix #6007: template backup: use minimized configuration for handling the full vm start

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

Am 24.01.25 um 11:08 schrieb Fiona Ebner:
> Previously, the template's configuration was used as-is for the rest
> of handling the VM start even if config_to_command() uses a minimized
> configuration to build the command. This can lead to issues with a
> network device with the 'link_down' flag set, because the network
> device will not be present, but the start handling will still issue a
> QMP command for it, leading to a failed backup operation.
> 
> Use the minimized configuration for the whole start-up handling to
> avoid such issues.
> 
> Use the 'no-write-config' flag to safeguard against accidentally
> writing out the temporarily modified config.
> 
> Suggested-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
>  PVE/QemuServer.pm | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index 808c0e1c..837b8916 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -3396,6 +3396,7 @@ sub config_to_command {
>  	    scsihw => $conf->{scsihw}, # so that the scsi disks are correctly added
>  	    bios => $conf->{bios}, # so efidisk gets included if it exists
>  	    name => $conf->{name}, # so it's correct in the process list
> +	    'no-write-config' => 1, # make sure to not write this configuration
>  	};
>  
>  	# copy all disks over
> @@ -4017,7 +4018,7 @@ sub config_to_command {
>  	push @$cmd, @$aa;
>      }
>  
> -    return wantarray ? ($cmd, $vollist, $spice_port, $pci_devices) : $cmd;
> +    return wantarray ? ($cmd, $vollist, $spice_port, $pci_devices, $conf) : $cmd;
>  }
>  

Hmm, thinking about it again, to reduce regression potential, we could
also just return the temporary config if it was actually required and
have the caller only assign it when really present.

>  sub check_rng_source {
> @@ -5613,8 +5614,17 @@ sub vm_start_nolock {
>  	print "Resuming suspended VM\n";
>      }
>  
> -    my ($cmd, $vollist, $spice_port, $pci_devices) = config_to_command($storecfg, $vmid,
> -	$conf, $defaults, $forcemachine, $forcecpu, $params->{'live-restore-backing'});
> +    # Note that for certain cases like templates, the configuration is minimized, so need to ensure
> +    # the rest of the function here uses the same configuration that was used to build the command
> +    (my $cmd, my $vollist, my $spice_port, my $pci_devices, $conf) = config_to_command(
> +	$storecfg,
> +	$vmid,
> +	$conf,
> +	$defaults,
> +	$forcemachine,
> +	$forcecpu,
> +	$params->{'live-restore-backing'},
> +    );
>  
>      my $migration_ip;
>      my $get_migration_ip = sub {



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