[Qemu-devel] multiple USB Serial devices qemu load

[Stefan Priebe - Profihost AG <s.priebe@profihost.ag>]

Hello,

i've 4 USB serial devices and one HID device i want to pass to a guest.

The passing itself works fine but while the guest has 0 load or cpu
usage the qemu process itself has around 40% cpu usage on a single 3,2
ghz E3 xeon.

I already tried xhci but it doesn't change anything. Also the latency of
the usb devices is very high and fluctuate. Qemu Version 1.7.1

Inside the guest:
# lsusb -t
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 480M
    |__ Port 1: Dev 2, If 0, Class=HID, Driver=usbhid, 480M
    |__ Port 2: Dev 3, If 0, Class=HID, Driver=usbfs, 12M
    |__ Port 3: Dev 4, If 0, Class=vend., Driver=ftdi_sio, 12M
    |__ Port 4: Dev 5, If 0, Class=hub, Driver=hub/8p, 12M
        |__ Port 1: Dev 6, If 0, Class=vend., Driver=ftdi_sio, 12M
        |__ Port 2: Dev 7, If 0, Class=comm., Driver=cdc_acm, 12M
        |__ Port 2: Dev 7, If 1, Class=data, Driver=cdc_acm, 12M
        |__ Port 3: Dev 8, If 0, Class=vend., Driver=ftdi_sio, 12M

Qremu command line:

qemu -pidfile /var/run/qemu-server/102.pid -daemonize -name test -smp
sockets=1,cores=1 -nodefaults -boot
menu=on,strict=on,reboot-timeout=1000 -vga cirrus -cpu
kvm64,+lahf_lm,+x2apic,+sep -k de -m 1024 -device
nec-usb-xhci,id=xhci,bus=pci.0,addr=0x1.0x2 -device
usb-tablet,id=tablet,bus=xhci.0,port=1 -device
usb-host,hostbus=2,hostport=1.2 -device usb-host,hostbus=2,hostport=1.3
-device usb-host,hostbus=2,hostport=1.4 -device
usb-host,hostbus=2,hostport=1.1.1 -device
usb-host,hostbus=2,hostport=1.1.4 -device
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 -device
virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5 -drive
file=/ssdstor/images/102/vm-102-disk-1.qcow2,if=none,id=drive-scsi0,format=qcow2,cache=writeback,discard=on,aio=native
-device
scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0
-netdev
type=tap,id=net0,ifname=tap102i0,script=/var/lib/qemu-server/pve-bridge,vhost=on
-device
virtio-net-pci,mac=3A:53:02:E3:76:59,netdev=net0,bus=pci.0,addr=0x12,id=net0,bootindex=300

Does anybody have an idea how to lower the CPU usage?

Greets,
Stefan