How to setup nvmetcli for FC loopback mode?

[nickchengster]

I got a problem about setting nvmetcli for FC loopback mode.
The configuration is a NVMe SSD, KC1000, from Kingston and a HBA, QLE2672
2-port 16Gb Fibre Channel Adapter, from QLogic and are installed on Linux
kernel 4.16.6.

The scenario is a fc loop mode, which uses the sole FC HBA as an initiator
and target, to access the NVMe SSD as a NVMe target.

I installed all the required drivers, i.e. nvme-core, nvme, nvme-fabrics,
nvme-fc, nvmet, nvmet-fc, nvme-loop, nvme-fcloop and qla2xxx, in order and
nvmetcli and followded through steps on
http://git.infradead.org/users/hch/nvmetcli.git/blob/HEAD:/Documentation/nvmetcli.txt
.

But when I reach line 212, "create testnqn", on the link above, I had error
message as
"Could not symlink testnqn in configFS: [Errno 6] No such device or
address".

I hacked the kernel source and found seemingly there are some device
attributes on the path, "/sys/devices/virtual/fcloop/ctl/", to fill. But I
can't figure out what strings and format are.

Please guide me, if you have any ideas.

Thank you,

[khalfella]

I needed to use nvmet fcloop and I had to figure this out too. I think you do not need a physical HBA to use fcloop. nvme fcloop target registers a LLDD (similar to what qla2xxxx does) that nvme initiator use directly, and I think this were the word "loop" comes from.

Here are the steps that worked for me

modprobe nvme-fcloop
echo 'wwnn=0x200000109b5f2955,wwpn=0x100000109b5f2955' > /sys/class/fcloop/ctl/add_local_port
echo 'lpwwnn=0x200000109b5f2955,lpwwpn=0x100000109b5f2955,wwnn=0x200000109b5f2956,wwpn=0x100000109b5f2956,roles=0x60' > /sys/class/fcloop/ctl/add_remote_port
echo 'wwnn=0x200000109b5f2956,wwpn=0x100000109b5f2956' > /sys/class/fcloop/ctl/add_target_port

These commands add local port, remote port, and the target port. This basically adds the loopback HBA and the remote port acts as the target.

# mount -t configfs configfs /sys/kernel/config/
# mkdir /sys/kernel/config/nvmet/subsystems/mysubsystem
# cd /sys/kernel/config/nvmet/subsystems/mysubsystem
# echo 1 > attr_allow_any_host
# mkdir namespaces/10
# cd namespaces/10
# echo -n /dev/nvme0n1 > device_path
# echo 1 > enable
# mkdir /sys/kernel/config/nvmet/ports/1
# cd /sys/kernel/config/nvmet/ports/1
# echo nn-0x200000109b5f2956,pn-0x100000109b5f2956 > addr_traddr
# echo fc > addr_trtype
# echo 4420 > addr_trsvcid
# echo fc > addr_adrfam
# cd /sys/kernel/config/nvmet/
# ln -s subsystems/mysubsystem/ ports/1/subsystems/

Create an nvme subsystem mysubsystem, add local device nvme0n1 as namespace 10, and configure an fc port that is linked to the subsystem. Note addr_traddr needs to match the target port.

# nvme discover --transport fc --traddr=nn-0x200000109b5f2956:pn-0x100000109b5f2956 --host-traddr=nn-0x200000109b5f2955:pn-0x100000109b5f2955
# nvme connect --transport fc --traddr=nn-0x200000109b5f2956:pn-0x100000109b5f2956 --host-traddr=nn-0x200000109b5f2955:pn-0x100000109b5f2955 -n mysubsystem

Discover and connect to the fcloop subsystem.