Re: [Qemu-devel] [PATCH 4/5] virtio-scsi: Add start/stop functionality for vhost-scsi

[Paolo Bonzini]

Il 14/09/2012 00:27, Nicholas A. Bellinger ha scritto:
> *) Keep vhost-scsi as a backend to virtio-scsi-pci
> 
>   - Reduces duplicated code amongst multiple virtio-scsi backends.
>   
>   - Follows the split for what existing vhost-net code already does.
> 
> So that said, two quick questions for Paolo & Co..
> 
> For the standalone vhost-scsi-pci device case, can you give a brief idea
> as to what extent you'd like to see virtio-scsi.c code/defs duplicated
> and/or shared amongst a new vhost-scsi-pci device..?

Not much, in the end, would be shared; it could end up being just
parts of virtio_scsi_init and virtio_scsi_exit, and virtio_scsi_get_config.

Almost all the other code is to implement the SCSI bus interface,
which you do not need.

I don't remember if and how vhost handles configuration changes.  If you
need any struct in virtio-scsi.c, either move it to virtio-scsi.h or
add the new device in the same file.

> Also to help me along, can you give an example based on the current
> usage below how the QEMU command line arguments would change with a
> standalone vhost-scsi-pci device..?
> 
> ./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -smp 4 -m 2048 \
>     -hda /usr/src/qemu-vhost.git/debian_squeeze_amd64_standard-old.qcow2 \
>     -vhost-scsi id=vhost-scsi0,wwpn=naa.600140579ad21088,tpgt=1 \
>     -device virtio-scsi-pci,vhost-scsi=vhost-scsi0,event_idx=off

Two possibilities.  Either simply do s/virtio-scsi-pci/vhost-scsi-pci/ or do

./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -smp 4 -m 2048 \
    -hda /usr/src/qemu-vhost.git/debian_squeeze_amd64_standard-old.qcow2 \
    -device virtio-scsi-pci,wwpn=naa.600140579ad21088,tpgt=1,event_idx=off