fix #1908: add vmgenid config/device

this adds a VM Generation ID device uses by Windows (Server) to determine
some specific actions that may have happened with the vm
such as rollback, restore, etc.

see:

https://docs.microsoft.com/en-us/windows/desktop/hyperv_v2/virtual-machine-generation-identifier

for details on how it works and when it should change

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

PVE/API2/Qemu.pm

@@ -599,6 +599,10 @@ __PACKAGE__->register_method({
 			$conf->{smbios1} = PVE::QemuServer::generate_smbios1_uuid();
 		    }
 
+		    if (!defined($conf->{vmgenid}) || $conf->{vmgenid} eq '1') {
+			$conf->{vmgenid} = PVE::QemuServer::generate_uuid();
+		    }
+
 		    PVE::QemuConfig->write_config($vmid, $conf);
 
 		};
@@ -1091,6 +1095,10 @@ my $update_vm_api  = sub {
 	    # add macaddr
 	    my $net = PVE::QemuServer::parse_net($param->{$opt});
 	    $param->{$opt} = PVE::QemuServer::print_net($net);
+	} elsif ($opt eq 'vmgenid') {
+	    if ($param->{$opt} eq '1') {
+		$param->{$opt} = PVE::QemuServer::generate_uuid();
+	    }
 	}
     }
 
@@ -2725,13 +2733,15 @@ __PACKAGE__->register_method({
 	    }
 
             # auto generate a new uuid
-            my ($uuid, $uuid_str);
-            UUID::generate($uuid);
-            UUID::unparse($uuid, $uuid_str);
 	    my $smbios1 = PVE::QemuServer::parse_smbios1($newconf->{smbios1} || '');
-	    $smbios1->{uuid} = $uuid_str;
+	    $smbios1->{uuid} = PVE::QemuServer::generate_uuid();
 	    $newconf->{smbios1} = PVE::QemuServer::print_smbios1($smbios1);
 
+	    # auto generate a new vmgenid if the option was set
+	    if ($newconf->{vmgenid}) {
+		$newconf->{vmgenid} = PVE::QemuServer::generate_uuid();
+	    }
+
 	    delete $newconf->{template};
 
 	    if ($param->{name}) {

PVE/CLI/qm.pm

@@ -621,6 +621,7 @@ __PACKAGE__->register_method ({
 
 	    eval {
 		# order matters, as do_import() will load_config() internally
+		$conf->{vmgenid} = PVE::QemuServer::generate_uuid();
 		$conf->{smbios1} = PVE::QemuServer::generate_smbios1_uuid();
 		PVE::QemuConfig->write_config($vmid, $conf);
 

PVE/QemuConfig.pm

@@ -300,6 +300,10 @@ sub __snapshot_rollback_hook {
 	    # in the original config.
 	    delete $conf->{machine} if $snap->{vmstate} && !defined($data->{oldmachine});
 	}
+
+	if ($conf->{vmgenid}) {
+	    $conf->{vmgenid} = PVE::QemuServer::generate_uuid();
+	}
     }
 
     return;

PVE/QemuServer.pm

@@ -559,6 +559,13 @@ EODESCR
 	description => "Select BIOS implementation.",
 	default => 'seabios',
     },
+    vmgenid => {
+	type => 'string',
+	pattern => '(?:[a-fA-F0-9]{8}(?:-[a-fA-F0-9]{4}){3}-[a-fA-F0-9]{12}|[01])',
+	format_description => 'UUID',
+        description => "Set VM Generation ID UUID. Use special value 1 to autogenerate one (API only). Use special value 0 to disable explicitly.",
+	optional => 1,
+    },
 };
 
 my $confdesc_cloudinit = {
@@ -3191,6 +3198,10 @@ sub config_to_command {
 	push @$cmd, '-smbios', "type=1,$conf->{smbios1}";
     }
 
+    if ($conf->{vmgenid}) {
+	push @$devices, '-device', 'vmgenid,guid='.$conf->{vmgenid};
+    }
+
     if ($conf->{bios} && $conf->{bios} eq 'ovmf') {
 	die "uefi base image not found\n" if ! -f $OVMF_CODE;
 
@@ -5554,6 +5565,13 @@ sub restore_update_config_line {
 	} else {
 	    print $outfd $line;
 	}
+    } elsif (($line =~ m/^(vmgenid: )(.*)/)) {
+	# always generate a new vmgenid
+	my $vmgenid = $2;
+	if ($vmgenid ne '0') {
+	    $vmgenid = generate_uuid();
+	}
+	print $outfd $1.$vmgenid."\n";
     } elsif (($line =~ m/^(smbios1: )(.*)/) && $unique) {
 	my ($uuid, $uuid_str);
 	UUID::generate($uuid);
@@ -6756,11 +6774,15 @@ sub resolve_first_disk {
     return $firstdisk;
 }
 
-sub generate_smbios1_uuid {
+sub generate_uuid {
     my ($uuid, $uuid_str);
     UUID::generate($uuid);
     UUID::unparse($uuid, $uuid_str);
-    return "uuid=$uuid_str";
+    return $uuid_str;
+}
+
+sub generate_smbios1_uuid {
+    return "uuid=".generate_uuid();
 }
 
 # bash completion helper