Description of problem:
After Hotplug virtio-serial-pci and ports during early stage booting of guest port wasn't shown in guest


Version-Release number of selected component (if applicable):
kernel-3.10.0-675.el7.ppc64le
qemu-kvm-rhev-2.9.0-7.el7.ppc64le
SLOF-20170303-4.git66d250e.el7.noarch

How reproducible:
2/5

Steps to Reproduce:

1.prerequisite
  boot up a guest with a chardev
  eg,/usr/libexec/qemu-kvm -name avocado-vt-vm1 -chardev socket,id=qmp_id_qmpmonitor1,path=/tmp/monitor-qmpmonitor1,server,nowait -mon chardev=qmp_id_qmpmonitor1,mode=control -sandbox on -machine pseries-rhel7.4.0 -nodefaults -vga std -chardev socket,id=serial_id_serial0,path=/tmp/ttt,server,nowait -device spapr-vty,reg=0x30000000,chardev=serial_id_serial0 -device nec-usb-xhci,id=usb1,bus=pci.0,addr=0x3 -device usb-kbd,id=input0 -device usb-mouse,id=input1 -drive id=drive_image1,if=none,snapshot=off,aio=native,cache=none,format=qcow2,file=rhel74-ppc64-virtio-scsi.qcow2 -device virtio-blk-pci,id=image1,drive=drive_image1,bootindex=1,bus=pci.0,addr=0x4 -device spapr-vlan,mac=9a:93:94:95:96:97,id=idpWdRJ9,netdev=idkTBKmY -netdev tap,id=idkTBKmY,vhost=on,script=/etc/qemu-ifup,downscript=/etc/qemu-down,id=hostnet1 -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pci.0,addr=0x6 -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=4 -vnc :1 -rtc base=utc,clock=host -boot order=cdn,once=d,menu=off,strict=off -enable-kvm -monitor stdio -monitor unix:/tmp/monitor3,server,nowait -qmp tcp:0:4444,server,nowait -m 8G,slots=32,maxmem=80G -numa node -chardev socket,id=channel1,path=/tmp/helloworld,server,nowait

2.During the early stage of booting 
(qemu) device_add virtio-serial-pci,id=virtio-serial0,max_ports=16
(qemu) device_add virtserialport,chardev=channel1,name=com.redhat.rhevm.vdsm,bus=virtio-serial0.0,id=port0

Actual results:
After login guest 
ls /dev/vp* to check the port,but it didn't exist.

Expected results:
The port was there 

Additional info:
Info qtree log after hotplug virtio-serail-pci and port
(qemu) info qtree
bus: main-system-bus
  type System
  dev: spapr-pci-host-bridge, id ""
    index = 0 (0x0)
    buid = 576460752840294400 (0x800000020000000)
    liobn = 2147483648 (0x80000000)
    liobn64 = 2147483649 (0x80000001)
    mem_win_addr = 35186519572480 (0x200080000000)
    mem_win_size = 2147483648 (0x80000000)
    mem64_win_addr = 36283883716608 (0x210000000000)
    mem64_win_size = 1099511627776 (0x10000000000)
    mem64_win_pciaddr = 36283883716608 (0x210000000000)
    io_win_addr = 35184372088832 (0x200000000000)
    io_win_size = 65536 (0x10000)
    dynamic-reconfiguration = true
    dma_win_addr = 0 (0x0)
    dma_win_size = 1073741824 (0x40000000)
    dma64_win_addr = 576460752303423488 (0x800000000000000)
    ddw = true
    pgsz = 69632 (0x11000)
    numa_node = 4294967295 (0xffffffff)
    pre-2.8-migration = false
    pcie-extended-configuration-space = true
    bus: pci.0
      type PCI
      dev: virtio-serial-pci, id "virtio-serial0"
        ioeventfd = true
        vectors = 2 (0x2)
        class = 1920 (0x780)
        virtio-pci-bus-master-bug-migration = false
        disable-legacy = "off"
        disable-modern = false
        migrate-extra = true
        modern-pio-notify = false
        x-disable-pcie = false
        page-per-vq = false
        x-ignore-backend-features = false
        ats = false
        x-pcie-deverr-init = true
        x-pcie-lnkctl-init = true
        x-pcie-pm-init = true
        addr = 01.0
        romfile = ""
        rombar = 1 (0x1)
        multifunction = false
        command_serr_enable = true
        x-pcie-lnksta-dllla = true
        x-pcie-extcap-init = true
        class Class 0780, addr 00:01.0, pci id 1af4:1003 (sub 1af4:0003)
        bar 0: i/o at 0xffffffffffffffff [0x3e]
        bar 1: mem at 0xffffffffffffffff [0xffe]
        bar 4: mem at 0xffffffffffffffff [0x3ffe]
        bus: virtio-bus
          type virtio-pci-bus
          dev: virtio-serial-device, id ""
            max_ports = 16 (0x10)
            emergency-write = true
            indirect_desc = true
            event_idx = true
            notify_on_empty = true
            any_layout = true
            iommu_platform = false
            __com.redhat_rhel6_ctrl_guest_workaround = false
            bus: virtio-serial0.0
              type virtio-serial-bus
              dev: virtserialport, id "port0"
                chardev = "channel1"
                nr = 1 (0x1)
                name = "com.redhat.rhevm.vdsm"
                port 1, guest off, host off, throttle off
      dev: virtio-scsi-pci, id "virtio_scsi_pci0"
        ioeventfd = true
        vectors = 4 (0x4)
        virtio-pci-bus-master-bug-migration = false
        disable-legacy = "off"
        disable-modern = false
        migrate-extra = true
        modern-pio-notify = false
        x-disable-pcie = false
        page-per-vq = false
        x-ignore-backend-features = false
        ats = false
        x-pcie-deverr-init = true
        x-pcie-lnkctl-init = true
        x-pcie-pm-init = true
        addr = 06.0
        romfile = ""
        rombar = 1 (0x1)
        multifunction = false
        command_serr_enable = true
        x-pcie-lnksta-dllla = true
        x-pcie-extcap-init = true
        class SCSI controller, addr 00:06.0, pci id 1af4:1004 (sub 1af4:0008)
        bar 0: i/o at 0x80 [0xbf]
        bar 1: mem at 0xc0025000 [0xc0025fff]
        bar 4: mem at 0x210000004000 [0x210000007fff]
        bus: virtio-bus
          type virtio-pci-bus
          dev: virtio-scsi-device, id ""
            num_queues = 1 (0x1)
            max_sectors = 65535 (0xffff)
            cmd_per_lun = 128 (0x80)
            hotplug = true
            param_change = true
            indirect_desc = true
            event_idx = true
            notify_on_empty = true
            any_layout = true
            iommu_platform = false
            __com.redhat_rhel6_ctrl_guest_workaround = false
            bus: virtio_scsi_pci0.0
              type SCSI
      dev: virtio-blk-pci, id "image1"
        class = 0 (0x0)
        ioeventfd = true
        vectors = 2 (0x2)
        virtio-pci-bus-master-bug-migration = false
        disable-legacy = "off"
        disable-modern = false
        migrate-extra = true
        modern-pio-notify = false
        x-disable-pcie = false
        page-per-vq = false
        x-ignore-backend-features = false
        ats = false
        x-pcie-deverr-init = true
        x-pcie-lnkctl-init = true
        x-pcie-pm-init = true
        addr = 04.0
        romfile = ""
        rombar = 1 (0x1)
        multifunction = false
        command_serr_enable = true
        x-pcie-lnksta-dllla = true
        x-pcie-extcap-init = true
        class SCSI controller, addr 00:04.0, pci id 1af4:1001 (sub 1af4:0002)
        bar 0: i/o at 0x40 [0x7f]
        bar 1: mem at 0xc0024000 [0xc0024fff]
        bar 4: mem at 0x210000000000 [0x210000003fff]
        bus: virtio-bus
          type virtio-pci-bus
          dev: virtio-blk-device, id ""
            drive = "drive_image1"
            logical_block_size = 512 (0x200)
            physical_block_size = 512 (0x200)
            min_io_size = 0 (0x0)
            opt_io_size = 0 (0x0)
            discard_granularity = 4294967295 (0xffffffff)
            write-cache = "auto"
            share-rw = false
            rerror = "auto"
            werror = "auto"
            cyls = 16383 (0x3fff)
            heads = 16 (0x10)
            secs = 63 (0x3f)
            serial = ""
            config-wce = true
            scsi = false
            request-merging = true
            num-queues = 1 (0x1)
            indirect_desc = true
            event_idx = true
            notify_on_empty = true
            any_layout = true
            iommu_platform = false
            __com.redhat_rhel6_ctrl_guest_workaround = false
      dev: nec-usb-xhci, id "usb1"
        msi = "auto"
        msix = "auto"
        superspeed-ports-first = true
        force-pcie-endcap = false
        intrs = 16 (0x10)
        slots = 64 (0x40)
        streams = true
        p2 = 4 (0x4)
        p3 = 4 (0x4)
        addr = 03.0
        romfile = ""
        rombar = 1 (0x1)
        multifunction = false
        command_serr_enable = true
        x-pcie-lnksta-dllla = true
        x-pcie-extcap-init = true
        class USB controller, addr 00:03.0, pci id 1033:0194 (sub 1af4:1100)
        bar 0: mem at 0xc0020000 [0xc0023fff]
        bus: usb1.0
          type usb-bus
          dev: usb-tablet, id "usb-tablet1"
            usb_version = 2 (0x2)
            display = ""
            head = 0 (0x0)
            port = "4"
            serial = ""
            full-path = true
            msos-desc = true
            addr 0.3, port 4, speed 480, name QEMU USB Tablet, attached
          dev: usb-mouse, id "input1"
            usb_version = 2 (0x2)
            port = ""
            serial = ""
            full-path = true
            msos-desc = true
            addr 0.2, port 2, speed 480, name QEMU USB Mouse, attached
          dev: usb-kbd, id "input0"
            usb_version = 2 (0x2)
            display = ""
            port = ""
            serial = ""
            full-path = true
            msos-desc = true
            addr 0.1, port 1, speed 480, name QEMU USB Keyboard, attached
      dev: VGA, id ""
        vgamem_mb = 16 (0x10)
        mmio = true
        qemu-extended-regs = true
        addr = 00.0
        romfile = "vgabios-stdvga.bin"
        rombar = 1 (0x1)
        multifunction = false
        command_serr_enable = true
        x-pcie-lnksta-dllla = true
        x-pcie-extcap-init = true
        class VGA controller, addr 00:00.0, pci id 1234:1111 (sub 1af4:1100)
        bar 0: mem at 0x80000000 [0x80ffffff]
        bar 2: mem at 0xc0000000 [0xc0000fff]
        bar 6: mem at 0xffffffffffffffff [0xfffe]
  dev: spapr-vio-bridge, id ""
    bus: spapr-vio
      type spapr-vio-bus
      dev: spapr-vlan, id "idpWdRJ9"
        reg = 1895825409 (0x71000001)
        mac = "9a:93:94:95:96:97"
        vlan = <null>
        netdev = "idkTBKmY"
        use-rx-buffer-pools = true
        irq = 4104 (0x1008)
      dev: spapr-vty, id "vty@30000000"
        reg = 805306368 (0x30000000)
        chardev = "serial_id_serial0"
        irq = 4103 (0x1007)
      dev: spapr-nvram, id "nvram@71000000"
        reg = 1895825408 (0x71000000)
        drive = ""
        irq = 4098 (0x1002)
  dev: spapr-rtc, id ""