Description of problem:
A domain with spiceport char device and without spice graphics, libvirt directly ignored the related -chardev options in qemu command line, started domain successfully.

Version-Release number of selected component (if applicable):
libvirt-1.2.7-1.el7.x86_64
qemu-kvm-rhev-2.1.0-1.el7.x86_64
kernel-3.10.0-138.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
Set a vnc graphics in domain xml as below:
    <graphics type='vnc' port='5900' autoport='yes' listen='127.0.0.1'>
      <listen type='address' address='127.0.0.1'/>
    </graphics>

[root@localhost libvirt-1.2.7]# virsh dumpxml r7 | grep spiceport -b4

1370:    <serial type='spiceport'>
1400-      <source channel='org.qemu.console.serial.0'/>
1452-      <target port='1'/>
1477-    </serial>
1491:    <console type='spiceport'>
1522-      <source channel='org.qemu.console.serial.0'/>
1574-      <target type='serial' port='1'/>
1613-    </console>

[root@localhost libvirt-1.2.7]# virsh start r7
Domain r7 started

[root@localhost ~]# ps aux | grep qemu-kvm
qemu      3469 23.6  7.4 1733864 580052 ?      Sl   16:58   0:24 /usr/libexec/qemu-kvm -name r7 -S -machine pc-i440fx-rhel7.0.0,accel=kvm,usb=off -m 1024 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -uuid 628e1918-eb89-4ded-8c10-f81e93b8eb7c -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/r7.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown -boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive file=/var/lib/libvirt/images/r7_latest.img,if=none,id=drive-ide0-0-0,format=raw,cache=none -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -netdev tap,fd=25,id=hostnet0 -device rtl8139,netdev=hostnet0,id=net0,mac=52:54:00:06:82:2b,bus=pci.0,addr=0x3 -vnc 127.0.0.1:0 -device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,bus=pci.0,addr=0x2 -device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 -msg timestamp=on

[root@localhost ~]# virsh list --all
 Id    Name                           State
----------------------------------------------------
 21    r7                             running

[root@localhost ~]# virsh dumpxml r7 | grep spiceport -b5
...
2104:    <serial type='spiceport'>
2134-      <source channel='org.qemu.console.serial.0'/>
2186-      <target port='1'/>
2211-      <alias name='serial0'/>
2241-    </serial>
2255:    <console type='spiceport'>
2286-      <source channel='org.qemu.console.serial.0'/>
2338-      <target type='serial' port='1'/>
2377-      <alias name='serial0'/>
2407-    </console>
...

Actual results:
As shown above steps, libvirt ignored the spiceport device continue to start domain.

[root@localhost libvirt-1.2.7]# grep "== VIR_DOMAIN_CHR_TYPE_SPICEPORT" ./src/qemu/qemu_command.c -b5
298519-
298520-    for (i = 0; i < def->nserials; i++) {
298562-        virDomainChrDefPtr serial = def->serials[i];
298615-        char *devstr;
298637-
298638:        if (serial->source.type == VIR_DOMAIN_CHR_TYPE_SPICEPORT && !spice)
298714-            continue;
298736-
298737-        /* Use -chardev with -device if they are available */
298799-        if (virQEMUCapsSupportsChardev(def, qemuCaps, serial)) {
298864-            virCommandAddArg(cmd, "-chardev");

 
Expected results:
Libvirt had better report a clear error message or do a sanity check before starting, rather than starting domain without such spiceport device in qemu command line.

Additional info:
From: man qemu-kvm
       -chardev spiceport ,id=id ,debug=debug, name=name
           spiceport is only available when spice support is built in.

           debug debug level for spicevmc

           name name of spice port to connect to

           Connect to a spice port, allowing a Spice client to handle the traffic identified by a name (preferably a fqdn).