Linux Virtualization - Oct 2009 - [PATCH 0/4] megaraid_sas HBA emulation

Hi all,

this patchset implements an emulation for the megaraid_sas HBA.
It provides emulates an LSI MegaRAID SAS 8708EM2 HBA, ie
presenting to the guest a virtual SCSI adapter.
Internally it is using aio for read/write requests and
either SG_IO or SCSI command emulation for everything else.

The reason for choosing the megaraid_sas HBA and not, say,
implementing a virtio scsi interface is because:
- the megaraid_sas is using a very simple firmware interface,
  comparable to virtio
- the HBA driver are already existent, so I only have to
  write the backend :-)

The device can be accessed by

-drive if=raid,file=XXX

In order to support SCSI command emulation I had to update /
patch up the existing SCSI disk support. This might be
not to everyones taste, so I'm open to alternative
suggestions.

But I certainly do _not_ want to update the SCSI disk
emulation, as this is really quite tied to the SCSI parallel
interface used by the old lsi53c895a.c.
Plus it doesn't do scatter-gather list handling, which
is quite impossible to fix without proper documentation.

Of course, if anyone else would step in here, I won't object :-)

It currently runs guests with 2.6.27 and up; Windows XP
support is not quite there yet. Anything else might work;
if not, enable debugging and sent me the logfile.

As usual, comment / suggestions  etc welcome.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare at suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: Markus Rex, HRB 16746 (AG N?rnberg)

Hi,
> The device can be accessed by
>
> -drive if=raid,file=XXX
Don't extend that qemu automagic please.  The new way to handle this is:

   -drive if=none,id=mydisk,file=/path/to/some/disk.img
   -device megasas,id=raid
   -device scsi-disk,bus=raid.0,scsi-id=1,drive=mydisk
> In order to support SCSI command emulation I had to update /
> patch up the existing SCSI disk support. This might be
> not to everyones taste, so I'm open to alternative
> suggestions.
>
> But I certainly do _not_ want to update the SCSI disk
> emulation, as this is really quite tied to the SCSI parallel
> interface used by the old lsi53c895a.c.
--verbose please.  I'd prefer to fix scsi-disk bugs and/or limitations 
instead of working around them.
> Plus it doesn't do scatter-gather list handling,
Which should be fixed anyway.

cheers,
   Gerd

> But I certainly do _not_ want to update the SCSI disk
> emulation, as this is really quite tied to the SCSI parallel
> interface used by the old lsi53c895a.c.
This is completely untrue. scsi-disk.c contains no transport-specific code. It 
is deliberately designed to be independent of both the transport (e.g. 
parallel SCSI or USB) and the mechanism by which the initiator transfers data 
to the host.

Paul