[pve-devel] [PATCH v9 qemu-server 1/6] Include "-cpu" parameter with live-migration

[Fabian Ebner]

On 26.03.20 16:13, Stefan Reiter wrote:
> This is required to support custom CPU models, since the
> "cpu-models.conf" file is not versioned, and can be changed while a VM
> using a custom model is running. Changing the file in such a state can
> lead to a different "-cpu" argument on the receiving side.
> 
> This patch fixes this by passing the entire "-cpu" option (extracted
> from /proc/.../cmdline) as a "qm start" parameter. Note that this is
> only done if the VM to migrate is using a custom model (which we can
> check just fine, since the <vmid>.conf *is* versioned with pending
> changes), thus not breaking any live-migration directionality.
> 
> Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
> ---
>   PVE/API2/Qemu.pm            |  8 +++++++-
>   PVE/QemuMigrate.pm          | 21 +++++++++++++++++++++
>   PVE/QemuServer.pm           | 13 +++++++++----
>   PVE/QemuServer/CPUConfig.pm |  2 ++
>   4 files changed, 39 insertions(+), 5 deletions(-)
> 
> diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm
> index ef8a7c3..80fd7ea 100644
> --- a/PVE/API2/Qemu.pm
> +++ b/PVE/API2/Qemu.pm
> @@ -2024,6 +2024,11 @@ __PACKAGE__->register_method({
>   		optional => 1,
>   	    },
>   	    machine => get_standard_option('pve-qemu-machine'),
> +	    'force-cpu' => {
> +		description => "Override QEMU's -cpu argument with the given string.",
> +		type => 'string',
> +		optional => 1,
> +	    },
>   	    targetstorage => {
>   		description => "Target storage for the migration. (Can be '1' to use the same storage id as on the source node.)",
>   		type => 'string',
> @@ -2052,6 +2057,7 @@ __PACKAGE__->register_method({
>   	my $timeout = extract_param($param, 'timeout');
>   
>   	my $machine = extract_param($param, 'machine');
> +	my $force_cpu = extract_param($param, 'force-cpu');
>   
>   	my $get_root_param = sub {
>   	    my $value = extract_param($param, $_[0]);
> @@ -2113,7 +2119,7 @@ __PACKAGE__->register_method({
>   
>   		PVE::QemuServer::vm_start($storecfg, $vmid, $stateuri, $skiplock, $migratedfrom, undef, $machine,
>   					  $spice_ticket, $migration_network, $migration_type, $targetstorage, $timeout,
> -					  $nbd_protocol_version);
> +					  $nbd_protocol_version, $force_cpu);
>   		return;
>   	    };
>   
> diff --git a/PVE/QemuMigrate.pm b/PVE/QemuMigrate.pm
> index 9cff64d..0604e33 100644
> --- a/PVE/QemuMigrate.pm
> +++ b/PVE/QemuMigrate.pm
> @@ -17,6 +17,7 @@ use PVE::ReplicationState;
>   use PVE::Storage;
>   use PVE::Tools;
>   
> +use PVE::QemuServer::CPUConfig;
>   use PVE::QemuServer::Drive;
>   use PVE::QemuServer::Helpers qw(min_version);
>   use PVE::QemuServer::Machine;
> @@ -227,7 +228,23 @@ sub prepare {
>   
>   	$self->{forcemachine} = PVE::QemuServer::Machine::qemu_machine_pxe($vmid, $conf);
>   
> +	# To support custom CPU types, we keep QEMU's "-cpu" parameter intact.
> +	# Since the parameter itself contains no reference to a custom model,
> +	# this makes migration independent of changes to "cpu-models.conf".
> +	if ($conf->{cpu}) {
> +	    my $cpuconf = PVE::QemuServer::CPUConfig::parse_cpu_conf_basic($conf->{cpu});
> +	    if ($cpuconf && PVE::QemuServer::CPUConfig::is_custom_model($cpuconf->{cputype})) {
> +		my $cmdline = PVE::QemuServer::Helpers::parse_cmdline($pid);
> +		die "could not read commandline of running machine\n"
> +		    if !$cmdline->{cpu}->{value};
> +
> +		# sanitize and untaint value
> +		$cmdline->{cpu}->{value} =~ $PVE::QemuServer::CPUConfig::qemu_cmdline_cpu_re;
> +		$self->{forcecpu} = $1;
> +	    }
> +	}
>       }

The parsing of the commandline here and in the next patch is the same, 
so a helper could be introduced for doing it.

> +
>       my $loc_res = PVE::QemuServer::check_local_resources($conf, 1);
>       if (scalar @$loc_res) {
>   	if ($self->{running} || !$self->{opts}->{force}) {
> @@ -645,6 +662,10 @@ sub phase2 {
>   	push @$cmd, '--machine', $self->{forcemachine};
>       }
>   
> +    if ($self->{forcecpu}) {
> +	push @$cmd, '--force-cpu', $self->{forcecpu};
> +    }
> +
>       if ($self->{online_local_volumes}) {
>   	push @$cmd, '--targetstorage', ($self->{opts}->{targetstorage} // '1');
>       }
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index a3e3269..98c2a9a 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -2911,7 +2911,7 @@ sub query_understood_cpu_flags {
>   }
>   
>   sub config_to_command {
> -    my ($storecfg, $vmid, $conf, $defaults, $forcemachine) = @_;
> +    my ($storecfg, $vmid, $conf, $defaults, $forcemachine, $force_cpu) = @_;
>   
>       my $cmd = [];
>       my $globalFlags = [];
> @@ -3311,7 +3311,12 @@ sub config_to_command {
>   	push @$rtcFlags, 'base=localtime';
>       }
>   
> -    push @$cmd, get_cpu_options($conf, $arch, $kvm, $kvm_off, $machine_version, $winversion, $gpu_passthrough);
> +    if ($force_cpu) {
> +	push @$cmd, '-cpu', $force_cpu;
> +    } else {
> +	push @$cmd, get_cpu_options($conf, $arch, $kvm, $kvm_off,
> +	    $machine_version, $winversion, $gpu_passthrough);
> +    }
>   
>       PVE::QemuServer::Memory::config($conf, $vmid, $sockets, $cores, $defaults, $hotplug_features, $cmd);
>   
> @@ -4706,7 +4711,7 @@ sub vmconfig_update_disk {
>   sub vm_start {
>       my ($storecfg, $vmid, $statefile, $skiplock, $migratedfrom, $paused,
>   	$forcemachine, $spice_ticket, $migration_network, $migration_type,
> -	$targetstorage, $timeout, $nbd_protocol_version) = @_;
> +	$targetstorage, $timeout, $nbd_protocol_version, $force_cpu) = @_;
>   
>       PVE::QemuConfig->lock_config($vmid, sub {
>   	my $conf = PVE::QemuConfig->load_config($vmid, $migratedfrom);
> @@ -4802,7 +4807,7 @@ sub vm_start {
>   	    print "Resuming suspended VM\n";
>   	}
>   
> -	my ($cmd, $vollist, $spice_port) = config_to_command($storecfg, $vmid, $conf, $defaults, $forcemachine);
> +	my ($cmd, $vollist, $spice_port) = config_to_command($storecfg, $vmid, $conf, $defaults, $forcemachine, $force_cpu);
>   
>   	my $migration_ip;
>   	my $get_migration_ip = sub {
> diff --git a/PVE/QemuServer/CPUConfig.pm b/PVE/QemuServer/CPUConfig.pm
> index 8a55739..4dcc6dc 100644
> --- a/PVE/QemuServer/CPUConfig.pm
> +++ b/PVE/QemuServer/CPUConfig.pm
> @@ -106,6 +106,8 @@ my @supported_cpu_flags = (
>   my $cpu_flag_supported_re = qr/([+-])(@{[join('|', @supported_cpu_flags)]})/;
>   my $cpu_flag_any_re = qr/([+-])([a-zA-Z0-9\-_\.]+)/;
>   
> +our $qemu_cmdline_cpu_re = qr/^((?>[+-]?[\w\-_=]+,?)+)$/;
> +
>   my $cpu_fmt = {
>       cputype => {
>   	description => "Emulated CPU type. Can be default or custom name (custom model names must be prefixed with 'custom-').",
>