kvm-arm: qemu always starts with drive in read-only mode

[Guido Haase <guweha@web.de>]

Hi folks,

once again I need your help.

On my cubietruck I installed jessie on microSD card.

My first goal is to get a VM running with kvm-arm and CPU based hw
virtualization started by qemu (for testing), later then started and
administrated by virsh.

Having installed the host system as described here

https://www.debian.org/releases/jessie/armhf/ch05s01.html.en #5.1.5

I installed qemu and libvirt-bin virtinst virt-top bridge-utils
afterwards. Also I checked some dmesg output to verify the
virtualization options of the CPU are ready for use and kvm-arm is
available:

    dmesg |grep SMP
    SMP: Total of 2 processors activated (96.00 BogoMIPS).

    dmesg |grep CPU
    CPU: All CPU(s) started in HYP mode.
    CPU: Virtualization extensions available.

    dmesg |grep kvm
    kvm [1]: interrupt-controller@1c84000 IRQ25
    kvm [1]: timer IRQ27
    kvm [1]: Hyp mode initialized successfully

I build a jessie bootstrap and put it into an *.img files so qemu can
use it. As hw to virtualize by qemu I choose a Versatile Express A15
board. I have a special dtb file and Kernel built with

    General setup -> Configure standard kernel features (expert users)
    General setup -> open by fhandle syscalls
    Enable the block layer -> Support for large (2TB+) block devices
                               and files

for this VM.

After I started the system by command

  qemu-system-arm -enable-kvm -smp 1 -m 256 -M vexpress-a15 -cpu host
  -kernel /home/guido/kvm-arm/jessie/vexpress-zImage -dtb
  /home/guido/kvm-arm/jessie/vexpress-v2p-ca15-tc1.dtb -append
  "root=/dev/vda console=ttyAMA0 rootwait" -drive
  if=none,file=/home/guido/kvm-arm/jessie/jessie-arm.img,id=factory
  -device virtio-blk-device,drive=factory -net
  nic,macaddr=02:fd:01:de:ad:34 -net tap -monitor null -serial stdio
  -nographic

the VM starts and I'm aible to login. Sadly, device jessie-arm.img i.e.
/dev/vda is allways mounted read-only. After loging into the VM I can
mount it read/write. But this no solution. I want the machine booting
with the device in read/write mode, because already during the boot
process some deamons try to write to it.

Just for testing I tried the same with a standard open suse image:

  qemu-system-arm -enable-kvm -smp 1 -m 256 -M vexpress-a15 -cpu host
  -kernel /home/guido/kvm-arm/opensuse/vexpress-zImage -dtb
  /home/guido/kvm-arm/opensuse/vexpress-v2p-ca15-tc1.dtb -append
  "root=/dev/vda console=ttyAMA0 rootwait" -drive
   if=none,file=/home/guido/kvm-arm/opensuse/opensuse-  factory.img,
   id=factory -device virtio-blk-device,drive=factory -net nic,
   macaddr=02:fd:01:de:ad:34-net tap -monitor null -serial stdio
   -nographic

The result is the same, booting fine but with /dev/sda in read-only
mode.

Any idea(s) what's going wrong?

Many thanks in advance,

Guido