Xen devel - Jul 2007 - [PATCH 0/4] PV SCSI driver (scsiback/scsifront)

Hi all.

We developped a first version PV SCSI.
(without a FC-SCSI driver by Kamada-san)

The change point is the following:
 * implement python code
   -> attach, detach, list support.
      Usage
      # xm scsihost-attach <Domain> scsi <SCSIHostno>
      # xm scsihost-detach <Domain> <SCSIHostno>
      # xm scsihost-list <Domain>
      <SCSIHostno> = scsi host number on Dom0

   -> python config
      scsihost = [''scsi,1'', ''type,num'']
                 type = "scsi"  (type=fc is current work by
Kamada-san)
                 num  = scsi host number on Dom0

 * performance tunning
   When many disks are connected with 1 HBA, many disk''s I/O request 
   will be issued to 1 RING.
   In this case, it becomes RING_FULL at once. 
   We made two RINGs (like a VNIF) because IO request must not save in RING.
   RING is used only to pass the command.



Best regards,
Tomonari Horikoshi



Tomonari Horikoshi wrote:----------------------
Sent:    Wed, 16 May 2007 18:08:27 +0900
Subject: [Xen-devel] [RFC] pv-scsi driver (scsiback/scsifront)
> 
> Hi all.
> 
>  We developped a pv-scsi driver that we refered Fujita-san''s
scsi-driver
>  and blkback.
>  (see,
http://www.xensource.com/files/xensummit_4/Xen_Summit_8_Matsumoto.pdf)
> 
>  The pv-scsi driver''s feature is as follow:
>   * Guest has dedicated SCSI-HBAs of Dom0.
>   * Guest can send scsi_cdb to the HBAs.
>   * Guest recognises the HBAs from hostno of xenstore.
> 
>  Currentlly, We are developping FC version based on this.
> 
> * Future work:
>   * implement python code
>   * performance tunning
>   * attach, detach
>   * suspend, resume
> 
snip ...




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On Fri, Jul 13, 2007 at 08:26:46PM +0900, Tomonari Horikoshi
wrote:
> 
> Hi all.
> 
> We developped a first version PV SCSI.
> (without a FC-SCSI driver by Kamada-san)
> 
> The change point is the following:
>  * implement python code
>    -> attach, detach, list support.
>       Usage
>       # xm scsihost-attach <Domain> scsi <SCSIHostno>
>       # xm scsihost-detach <Domain> <SCSIHostno>
>       # xm scsihost-list <Domain>
>       <SCSIHostno> = scsi host number on Dom0
> 
Hi!

Can you tell more about this patch..

The whole HBA is mapped to the guest.. Is the access to the devices on that
HBA exclusive for the guest, or can some of the devices be used on dom0 and
some on domU ?

Any plans to write single lun/id mapping code? 

-- Pasi

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Hi Pasi-san.

Thanks for your comment.


Pasi wrote:----------------------
Sent:    Mon, 16 Jul 2007 13:43:48 +0300
Subject: Re: [Xen-devel] [PATCH 0/4] PV SCSI driver (scsiback/scsifront)
> On Fri, Jul 13, 2007 at 08:26:46PM +0900, Tomonari Horikoshi wrote:
> > 
> > Hi all.
> > 
> > We developped a first version PV SCSI.
> > (without a FC-SCSI driver by Kamada-san)
> > 
> > The change point is the following:
> >  * implement python code
> >    -> attach, detach, list support.
> >       Usage
> >       # xm scsihost-attach <Domain> scsi <SCSIHostno>
> >       # xm scsihost-detach <Domain> <SCSIHostno>
> >       # xm scsihost-list <Domain>
> >       <SCSIHostno> = scsi host number on Dom0
> > 
> 
> Hi!
> 
> Can you tell more about this patch..
> 
> The whole HBA is mapped to the guest.. Is the access to the devices on that
> HBA exclusive for the guest, or can some of the devices be used on dom0 and
> some on domU ?
> 
> Any plans to write single lun/id mapping code? 
> 
> -- Pasi
This driver is not HBA exclusive for the guest.
Therefore, another guest cannot use the device on same HBA. 

We will develop the method to allocate to the guest by the unit of targetid.


---------------------

The Backend driver is issuing SCSI CDB to the Native SCSI as follows,
  * It gets "struct scsi_device" by using
"scsi_device_lookup()".
    At this time, the host_no uses the number of Native of backend domain.
    Besides (target_id, channel_id, lun_id), it uses the number sent from
    request.
  * It map DMA by using granttable.(like a VBD)
  * It issues the SCSI command by "blk_execute_rq_nowait()" by using 
    guest''s SCSI CDB.


Best regards,
Tomonari Horikoshi



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