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    Subjectabout NPIV with qemu-kvm.
    hi, hannes:

    I want to use NPIV with qemu-kvm, I issued the following command:

    echo '1111222233334444:5555666677778888' >

    and it will produce a new host6 and one vport succesfully, but it
    does not create any virtual hba pci device. so I don't know how to
    assign the virtual host to qemu-kvm.

    from your this mail, does array will first need to assign a lun to
    this vport? and through this new created disk, like device /dev/sdf,
    then I add qemu-kvm with -drive file=/dev/sdf,if=virtio... arguments?



    2011/6/29, Hannes Reinecke <>:
    > On 06/29/2011 12:07 PM, Christoph Hellwig wrote:
    >> On Wed, Jun 29, 2011 at 10:39:42AM +0100, Stefan Hajnoczi wrote:
    >>> I think we're missing a level of addressing. We need the ability to
    >>> talk to multiple target ports in order for "list target ports" to make
    >>> sense. Right now there is one implicit target that handles all
    >>> commands. That means there is one fixed I_T Nexus.
    >>> If we introduce "list target ports" we also need a way to say "This
    >>> CDB is destined for target port #0". Then it is possible to enumerate
    >>> target ports and address targets independently of the LUN field in the
    >>> CDB.
    >>> I'm pretty sure this is also how SAS and other transports work. In
    >>> their framing they include the target port.
    >> Yes, exactly. Hierachial LUNs are a nasty fringe feature that we should
    >> avoid as much as possible, that is for everything but IBM vSCSI which is
    >> braindead enough to force them.
    > Yep.
    >>> The question is whether we really need to support multiple targets on
    >>> a virtio-scsi adapter or not. If you are selectively mapping LUNs
    >>> that the guest may access, then multiple targets are not necessary.
    >>> If we want to do pass-through of the entire SCSI bus then we need
    >>> multiple targets but I'm not sure if there are other challenges like
    >>> dependencies on the transport (Fibre Channel, SAS, etc) which make it
    >>> impossible to pass through bus-level access?
    >> I don't think bus-level pass through is either easily possible nor
    >> desirable. What multiple targets are useful for is allowing more
    >> virtual disks than we have virtual PCI slots. We could do this by
    >> supporting multiple LUNs, but given that many SCSI ressources are
    >> target-based doing multiple targets most likely is the more scabale
    >> and more logical variant. E.g. we could much more easily have one
    >> virtqueue per target than per LUN.
    > The general idea here is that we can support NPIV.
    > With NPIV we'll have several scsi_hosts, each of which is assigned a
    > different set of LUNs by the array.
    > With virtio we need to able to react on LUN remapping on the array
    > side, ie we need to be able to issue a 'REPORT LUNS' command and
    > add/remove LUNs on the fly. This means we have to expose the
    > scsi_host in some way via virtio.
    > This is impossible with a one-to-one mapping between targets and
    > LUNs. The actual bus-level pass-through will be just on the SCSI
    > layer, ie 'REPORT LUNS' should be possible. If and how we do a LUN
    > remapping internally on the host is a totally different matter.
    > Same goes for the transport details; I doubt we will expose all the
    > dingy details of the various transports, but rather restrict
    > ourselves to an abstract transport.
    > Cheers,
    > Hannes
    > --
    > Dr. Hannes Reinecke zSeries & Storage
    > +49 911 74053 688
    > SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
    > GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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