Re: scsi layer interfaces for hypervisors

[James Smart <James.Smart@Emulex.Com>]

Siva,

I'm curious to hear how you position this against the pvscsi effort
going on in the Xen world.

-- james s

Siva Kodiganti wrote:
> Hello Linux community,
> 
>  A Project page for Virt_HBA is created on source forge.
>  https://sourceforge.net/projects/npivhba
> 
>  Project Virt_HBA is targeted for a providing patch for
>  Linux kernels to provide set of scsi layer interfaces to
>  aid Hypervisors in Linux to export Scsi Hosts to Guest
>  VMs.  Using these interfaces  Hypervisors could export
>  Scsi_Host of a virtual hba emulated by HBA hardware to
>  Guest VMs.  FC, and FCOE (may) have support for Nport
>  Virtualization, a FW/HW mechanism to emulate multiple
>  hbas(nports) using a single HBA HW.  Qlogic, and
>  Emulex have support for FC NPIV.  With this mechanism,
>  Hypervisor would be capable of mapping appropriate
>  Guest VM's shost queuecommand to underlying NPIV host's
>  queue_command, and other hostt relevant entry points(one
>  to one mapping).  This could also provide a means of
>  security for luns exported through NPIV host to be
>  visible for appropriate Guest OS, hiding from HostOS.
> 
>  Scsi Layer interfaces:
> 
>  Hypervisor's registration with scsi layer
> 
>  scsi_register_hypertt(xn_hostt, xsize);
>  xsize is size of private structure maintained by
>  hypervisor per npiv host.
> 
>  struct scsi_hyper_hostt xn_hostt {
>          .hyp_module             = "xn",
>          .hyp_psize              = size of( xhost);
>          .hyp_alloc_vhost        = xn_alloc_vhost,
>          .hyp_add_vhost          = xn_add_vhost,
>          .hyp_remove_vhost       = xn_remove_vhost,
>          .hyp_trans_func         = xn_trans_vhost,
>          .hyp_async_notifier     = xn_async_ntfr,
>          .hyp_reboot_notifier    = xn_reboot_ntfr,
>  };
> 
>  Scsi_Host {
> 
>          /* flag for FC or FCOE hw or fw hba virtulization */
>          unsigned virt_host:1;
> 
>  }
> 
>  scsi_alloc_host(), scsi_add_host(), and scsi_remove_host()
>  interfaces notify registered hypervisor about FC/FCOE
>  virtual Scsi_Host.  scsi_alloc_host() would allocate private
>  data area per scsi_host for registered hypervisors, which
>  export to Guest VMs.
> 
>  Hypervisors uses these virtual hosts' lld driver hostt entry
>  points to queue,abort,etc scsi commands to HBA driver directly
>  bypassing Host BlK, SD layers.
> 
>  Thanks,
>  Siva
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