Re: [Qemu-devel] [RFC-v2 4/6] virtio-scsi: Add start/stop functionality for vhost-scsi

[Stefan Hajnoczi]

On Mon, Aug 20, 2012 at 10:04 AM, Paolo Bonzini <address@hidden> wrote:
> Il 13/08/2012 10:35, Nicholas A. Bellinger ha scritto:
>> From: Stefan Hajnoczi <address@hidden>
>>
>> This patch starts and stops vhost as the virtio device transitions
>> through its status phases.  Vhost can only be started once the guest
>> reports its driver has successfully initialized, which means the
>> virtqueues have been set up by the guest.
>>
>> v2: - Squash virtio-scsi: use the vhost-scsi host device from stefan (nab)
>>     - Fix up virtio_scsi_properties[] conflict w/ upstream qemu (nab)
>>     - Drop usage of to_virtio_scsi() in virtio_scsi_set_status()
>>       (reported by paolo)
>>     - Use modern VirtIOSCSIConf define in virtio-scsi.h (reported by paolo)
>>     - Use s->conf->vhost_scsi instead of proxyconf->vhost_scsi in
>>       virtio_scsi_init() (reported by paolo)
>>     - Only register QEMU SCSI bus is vhost-scsi is not active (reported
>>       by paolo)
>
> How much of the functionality of virtio-scsi.[ch] is still in use at
> this point?  Would it make more sense to use a separate vhost-scsi-pci
> device instead?

Since the SCSI target lives in the kernel, almost everything is driven
from tcm_vhost.ko.  tcm_vhost.ko basically implements the full device
so I see the argument for -device vhost-scsi-pci.

> Especially since advertising VIRTIO_SCSI_F_HOTPLUG and
> VIRTIO_SCSI_F_CHANGE is probably wrong for vhost-scsi...

vhost participates in feature bit negotiation, see
VHOST_GET_FEATURES/VHOST_SET_FEATURES ioctls.

Stefan