Description of problem:

Can not boot up guest with scsi-generic device via -blockdev

QEMU 2.12.0 monitor - type 'help' for more information
(qemu) qemu-kvm: -device scsi-generic,drive=drive2,id=data-disk1,bus=scsi1.0: Device doesn't support drive option werror



Version-Release number of selected component (if applicable):

kernel-3.10.0-949.el7.x86_64
qemu-kvm-rhev-2.12.0-16.el7



How reproducible:
100%


Steps to Reproduce:

1. display mapping SCSI devices on host.
# sg_map
/dev/sg0  /dev/sr0
/dev/sg1  /dev/sda
/dev/sg2
/dev/sg3  /dev/sdb
/dev/sg4  /dev/sdc
/dev/sg5  /dev/sdd
/dev/sg6  /dev/sde

2. boot guest with scsi-generic via -blockdev
/usr/libexec/qemu-kvm \
    -S  \
    -name 'avocado-vt-vm1'  \
    -sandbox off  \
    -machine pc  \
    -nodefaults \
    -device VGA,bus=pci.0,addr=0x2  \
    -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/avocado_nCcZP2/monitor-qmpmonitor1-20180912-022419-cHHd8c59,server,nowait \
    -mon chardev=qmp_id_qmpmonitor1,mode=control  \
    -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/avocado_nCcZP2/monitor-catch_monitor-20180912-022419-cHHd8c59,server,nowait \
    -mon chardev=qmp_id_catch_monitor,mode=control \
    -device pvpanic,ioport=0x505,id=idQpDEaT  \
    -chardev socket,id=serial_id_serial0,path=/var/tmp/avocado_nCcZP2/serial-serial0-20180912-022419-cHHd8c59,server,nowait \
    -device isa-serial,chardev=serial_id_serial0  \
    -chardev socket,id=seabioslog_id_20180912-022419-cHHd8c59,path=/var/tmp/avocado_nCcZP2/seabios-20180912-022419-cHHd8c59,server,nowait \
    -device isa-debugcon,chardev=seabioslog_id_20180912-022419-cHHd8c59,iobase=0x402 \
    -device nec-usb-xhci,id=usb1,bus=pci.0,addr=0x3 \
    -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pci.0,addr=0x4 \
    -blockdev driver=file,cache.direct=off,cache.no-flush=on,filename=/home/rhel76-64-virtio-scsi.qcow2,node-name=my_file \
    -blockdev driver=qcow2,node-name=my,file=my_file \
    -device scsi-hd,drive=my,bus=virtio_scsi_pci0.0 \
    -device virtio-net-pci,mac=9a:ad:ae:af:b0:b1,id=id942Wof,vectors=4,netdev=idirzdj4,bus=pci.0,addr=0x5  \
    -netdev tap,id=idirzdj4,vhost=on \
    -m 2G  \
    -smp 4,maxcpus=4,cores=2,threads=1,sockets=2  \
    -cpu 'SandyBridge',+kvm_pv_unhalt \
    -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1  \
    -vnc :0  \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot menu=off,strict=off,order=cdn,once=d  \
    -enable-kvm \
    -monitor stdio \
    -qmp tcp:0:4444,server,nowait \
    -device virtio-scsi-pci,id=scsi1,bus=pci.0,addr=0x6 \
    -blockdev driver=raw,file.driver=host_device,cache.direct=off,cache.no-flush=on,file.filename=/dev/sg6,node-name=drive2 \
    -device scsi-generic,drive=drive2,id=data-disk1,bus=scsi1.0 \
    
   
Actual results:
after step 2,
QEMU 2.12.0 monitor - type 'help' for more information
(qemu) qemu-kvm: -device scsi-generic,drive=drive2,id=data-disk1,bus=scsi1.0: Device doesn't support drive option werror


Expected results:
Guest boot up normally.
If it doesn't support, the hint information is not clear.


Additional info:

Also hit this issue on RHEL7.5
kernel-3.10.0-862.14.3.el7.x86_64
qemu-kvm-rhev-2.10.0-21.el7_5.7


Guest can boot up normally with scsi-block device via -blockdev

-device virtio-scsi-pci,id=scsi1,bus=pci.0,addr=0x6 \
-blockdev driver=raw,file.driver=host_device,cache.direct=off,cache.no-flush=on,file.filename=/dev/sde,node-name=drive2 \
-device scsi-block,drive=drive2,id=data-disk1,bus=scsi1.0 \



Guest can boot up normally with scsi-generic device via drive

-device virtio-scsi-pci,id=bus1,bus=pci.0 \
-drive file=/dev/sg6,if=none,format=raw,snapshot=off,aio=threads,cache=writethrough,id=scsi-disk0 \
-device scsi-generic,bus=bus1.0,drive=scsi-disk0,id=disk \