[pve-devel] [PATCH v6 qemu-server 11/12] Include "-cpu" parameter with live-migration

[Stefan Reiter]

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>
---

New in v6! Technically independant from the rest of the series, but
live-migrating VMs with custom models would be broken in some cases.


 PVE/API2/Qemu.pm   |  9 ++++++++-
 PVE/QemuMigrate.pm | 22 ++++++++++++++++++++++
 PVE/QemuServer.pm  | 14 ++++++++++----
 3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm
index ed4e522..c80d756 100644
--- a/PVE/API2/Qemu.pm
+++ b/PVE/API2/Qemu.pm
@@ -1969,6 +1969,11 @@ __PACKAGE__->register_method({
 		optional => 1,
 	    },
 	    machine => get_standard_option('pve-qm-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',
@@ -1989,6 +1994,7 @@ __PACKAGE__->register_method({
 	my $vmid = extract_param($param, 'vmid');
 
 	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]);
@@ -2041,7 +2047,8 @@ __PACKAGE__->register_method({
 		syslog('info', "start VM $vmid: $upid\n");
 
 		PVE::QemuServer::vm_start($storecfg, $vmid, $stateuri, $skiplock, $migratedfrom, undef,
-					  $machine, $spice_ticket, $migration_network, $migration_type, $targetstorage);
+					  $machine, $spice_ticket, $migration_network, $migration_type,
+					  $targetstorage, $force_cpu);
 		return;
 	    };
 
diff --git a/PVE/QemuMigrate.pm b/PVE/QemuMigrate.pm
index d3e434c..5ac72cf 100644
--- a/PVE/QemuMigrate.pm
+++ b/PVE/QemuMigrate.pm
@@ -11,6 +11,8 @@ use PVE::Tools;
 use PVE::Cluster;
 use PVE::Storage;
 use PVE::QemuServer;
+use PVE::QemuServer::CPUConfig;
+use PVE::QemuServer::Helpers;
 use PVE::QemuServer::Machine;
 use PVE::QemuServer::Monitor qw(mon_cmd);
 use Time::HiRes qw( usleep );
@@ -219,7 +221,23 @@ 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
+		$cmdline->{cpu}->{value} =~ m/^((?>[+-]?[\w\-_=]+,?)+)$/;
+		$self->{forcecpu} = $1;
+	    }
+	}
     }
+
     my $loc_res = PVE::QemuServer::check_local_resources($conf, 1);
     if (scalar @$loc_res) {
 	if ($self->{running} || !$self->{opts}->{force}) {
@@ -573,6 +591,10 @@ sub phase2 {
 	push @$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 f06da2a..fe68d89 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -3381,7 +3381,7 @@ 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 $globalFlags = [];
@@ -3764,7 +3764,12 @@ sub config_to_command {
 	push @$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);
 
@@ -5118,7 +5123,8 @@ sub vmconfig_update_disk {
 
 sub vm_start {
     my ($storecfg, $vmid, $statefile, $skiplock, $migratedfrom, $paused,
-	$forcemachine, $spice_ticket, $migration_network, $migration_type, $targetstorage) = @_;
+	$forcemachine, $spice_ticket, $migration_network, $migration_type,
+	$targetstorage, $force_cpu) = @_;
 
     PVE::QemuConfig->lock_config($vmid, sub {
 	my $conf = PVE::QemuConfig->load_config($vmid, $migratedfrom);
@@ -5204,7 +5210,7 @@ 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 {
-- 
2.20.1