[openib-general] FW: [PATCH fixed] [RFC] IB/srp: enable multiple connections to the same target

[Lakshmanan, Madhu]

> From: Michael S. Tsirkin [mailto:mst at mellanox.co.il]
> 
> Quoting r. Lakshmanan, Madhu <mlakshmanan at silverstorm.com>:
> > Subject: RE: FW: [PATCH fixed] [RFC] IB/srp: enable multiple
connections
> to the same target
> >
> > > > I tested the patches, which are included in OFED 1.1 RC7,
against
> > > > Silverstorm SRP targets. The patch breaks backward compatibility
for
> > > > fabrics that use Silverstorm targets, due to the following:
> > > >
> > > > It defaults the new parameter "initiator_ext" to 0. Silverstorm
SRP
> > > > targets, when configured for working with OFED stacks, are
usually
> > set
> > > > to expect an initiator extension of 1, to overcome the earlier
> > > > limitation of OFED stacks setting initiator extension to the
port
> > > > number.
> > >
> > > Sounds like a target bug - why does it expect *anything* specific
> > > in the initiator extension?
> >
> > The Silverstorm SRP targets can be configured to accept connections
from
> >
> > specific hosts (identified by GUID) and / or specific initiator
> > extensions.
> > This allows for a scenario where a group of hosts can gain access to
the
> > same back-end storage device, by using the same initiator extension
> > across all the hosts, with the host GUID being ignored / wildcarded
on
> > the SRP target. It also facilitates a level of access control to
> > back-end storage devices and permits the grouping of hosts into
logical
> > groups.
> >
> > In order to interoperate successfully with the OFED 1.0 stack, such
SRP
> > targets were configured to expect the initiator extension reported
by
> > the OFED 1.0 SRP implementation, i.e. an initiator extension of 1.
Note
> > that
> > for this particular configuration the host GUID is wildcarded, and
the
> > only
> > unique identifier is the initiator extension.
> >
> > > > 1. Release note the above requirement of adding the
> > "initiator_ext=<n>"
> > > > string to the add target echo string, for all Silverstorm
targets.
> > >
> > > I don't think we'll be touching OFED 1.1 anymore. So maybe this is
> > > the best choice for kernel.org, too.
> > >
> >
> > Are the release notes / docs frozen as well?
> 
> Not yet.
> 
> > > > 2. Maintain the earlier default of the initiator extension being
> equal
> > > > to the port number.
> > >
> > > Hmm. What, exactly, is the target assumption?
> >
> > The target doesn't assume or default anything. It is how it is
> > configured. The current patch breaks existing Silverstorm SRP target
> > configurations, unless either:
> > 1. The user specifies the "initiator_ext=<n>" when adding a target,
> > which is not to be found anywhere in the release notes, or
> > 2. The configuration on the SRP target is modified to reflect the
> > changes in OFED 1.1 where the initiator extension is passed to the
> > target as 0, if the user doesn't specify it, which again is not
> > specified in the release notes.
> 
> OK,thanks.
> So we need to document this.
> Could you pls post a short text describing the issue,
> who is affected and what needs to be done by the user?
> 
> --
> MST

Vendor specific notes:

    Hosts that are connected to Silverstorm SRP targets need to do
either of the following steps after they are upgraded to the OFED 1.1
release in order to continue to access their storage successfully:

1. When issuing the "echo" command to add a new SRP target, the host
must append the string ",initiator_ext=0000000000000001" to the original
echo string. 
    Example: 

	If 'ibsrpdm -c' shows, and you want to connect to the first
target:

	
id_ext=0000000000000001,ioc_guid=00066a0138000165,dgid=fe8000000000000
000066a0260000165,pkey=ffff,service_id=0000494353535250,io_class=ff00
	
id_ext=0000000000000001,ioc_guid=00066a0238000165,dgid=fe8000000000000
000066a0260000165,pkey=ffff,service_id=0000494353535250,io_class=ff00

	the echo command must be:

	echo -n
id_ext=0000000000000001,ioc_guid=00066a0138000165,dgid=fe8000000000000
000066a0260000165,pkey=ffff,service_id=0000494353535250,io_class=ff00,
initiator_ext=0000000000000001
	> /sys/class/inifiniband_srp/srp-mthca0-1/add_target

OR

2. Change the SRP map on the Silverstorm SRP target to set the expected
initiator extension to 0. For details on how to change the SRP map on a
Silverstorm SRP target, please refer to product documentation.