Description of problem:
Redirecting usb device can be found in guest during first start . But the optional element "version" will be changed after saving into guest xml , and also be changed after reboot the guest  ; so redirecting usb device cannot be found in guest if I specify the redirfilter version .


version
kernel-3.10.0-234.el7.x86_64
qemu-kvm-rhev-2.2.0-8.el7.x86_64
libvirt-1.2.14-1.el7.x86_64

How reproducible:
100%

step to reproduce :

1.prepare a usb device .

# lsusb -v | grep SanDisk -A 9
Bus 002 Device 003: ID 0781:5567 SanDisk Corp. Cruzer Blade
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x0781 SanDisk Corp.
  idProduct          0x5567 Cruzer Blade
  bcdDevice            2.01                     <=== the version value
  iManufacturer           1 SanDisk
  iProduct                2 Cruzer Blade
  iSerial                 3 4C532000010510102461
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           32
    bNumInterfaces          1
    bConfigurationValue     1


2. prepare a healthy guest and add follow xml into guest , then start the guest

#virsh edit r7.1
......
  <redirdev bus='usb' type='spicevmc'>
      <alias name='redir0'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir1'/>
    </redirdev>
    <redirfilter>
      <usbdev class='0x08' vendor='0x0781' product='0x5567' version='2.01' allow='yes'/>
      <usbdev allow='no'/>
    </redirfilter>

save the xml and start the guest , check qemu CLI and guest xml:
#ps -ef|grep qemu
......
-chardev spicevmc,id=charredir0,name=usbredir -device usb-redir,chardev=charredir0,id=redir0,filter=0x08:0x0781:0x5567:0x0201:1|-1:-1:-1:-1:0 -chardev spicevmc,id=charredir1,name=usbredir -device usb-redir,chardev=charredir1,id=redir1,filter=0x08:0x0781:0x5567:0x0201:1|-1:-1:-1:-1:0
......


#virsh dumpxml r7.1 | grep redirdev -A 9
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir0'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir1'/>
    </redirdev>
    <redirfilter>
      <usbdev class='0x08' vendor='0x0781' product='0x5567' version='2.1' allow='yes'/>   <=== the value of version was changed to 2.1 after saved.
      <usbdev allow='no'/>
    </redirfilter>

3.using virt-viewer to check into guest , the usb device can be found in guest and can be added into guest through file->USB Device selection.
#virt-viewer r7.1
......

4. reboot guest . using virt-viewer to check again
# virsh destroy r7.1;virsh start r7.1
Domain r7.1 destroyed

Domain r7.1 started

# virsh dumpxml r7.1 | grep redirdev -A 9
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir0'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir1'/>
    </redirdev>
    <redirfilter>
      <usbdev class='0x08' vendor='0x0781' product='0x5567' version='2.10' allow='yes'/> <=== the value of version was changed to 2.10 after reboot guest
      <usbdev allow='no'/>
    </redirfilter>

check qemu CLI :
#ps -ef|grep qemu
......
 -device usb-redir,chardev=charredir0,id=redir0,filter=0x08:0x0781:0x5567:0x0210:1|-1:-1:-1:-1:0 -chardev spicevmc,id=charredir1,name=usbredir -device usb-redir,chardev=charredir1,id=redir1,filter=0x08:0x0781:0x5567:0x0210:1|-1:-1:-1:-1:0 -

5.using virt-viewer to check into guest , the usb device CANNOT be redirected into guest.

Actual results:
As step 4 and step 5 , the value of version was changed , so the usb device cannot be redirected into guest .

Expected results:
The usb device should always be found in the guest .