On 18/07/2017 18:32, Marc-André Lureau wrote: > > > On Thu, Jun 15, 2017 at 1:20 PM Paolo Bonzini <pbonz...@redhat.com > <mailto:pbonz...@redhat.com>> wrote: > > From: Felipe Franciosi <fel...@nutanix.com <mailto:fel...@nutanix.com>> > > This commit introduces a vhost-user device for SCSI. This is based > on the existing vhost-scsi implementation, but done over vhost-user > instead. It also uses a chardev to connect to the backend. Unlike > vhost-scsi (today), VMs using vhost-user-scsi can be live migrated. > > To use it, start Qemu with a command line equivalent to: > > qemu-system-x86_64 \ > -chardev socket,id=vus0,path=/tmp/vus.sock \ > -device vhost-user-scsi-pci,chardev=vus0,bus=pci.0,addr=... > > A separate commit presents a sample application linked with libiscsi to > provide a backend for vhost-user-scsi. > > Signed-off-by: Felipe Franciosi <fel...@nutanix.com > <mailto:fel...@nutanix.com>> > Message-Id: <1488479153-21203-4-git-send-email-fel...@nutanix.com > <mailto:1488479153-21203-4-git-send-email-fel...@nutanix.com>> > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com > <mailto:pbonz...@redhat.com>> > --- > > > I just realized the patch was missing qemu-options.hx update. Oh wait, > virtio-scsi-pci isn't documented either? > > Would it have been possible to add a vhost-user-chr=chr argument on > virtio-scsi-pci instead of introducing a new device? Would that make > sense (to share code, argument etc)?
No, it wouldn't make sense. The reason is that vhost-scsi devices are configured entirely outside QEMU, and for this reason vhost-scsi/vhost-user-scsi do not expose a SCSI bus at the QEMU level. They do share code (through the virtio-scsi-common superclass), but they are fundamentally different. The vhost-blk device probably would also be a separate class, for the same reason. There is no way to define a -drive option with a chardev backend. Even vhost-user-net is somewhat hackish in its use of -netdev in my opinion, because it cannot implement ->receive (except for the RARP hack) and it bypasses things such as filters and hubs. Paolo
