^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) =================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) Chelsio S3 iSCSI Driver for Linux
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) =================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) Introduction
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) The Chelsio T3 ASIC based Adapters (S310, S320, S302, S304, Mezz cards, etc.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) series of products) support iSCSI acceleration and iSCSI Direct Data Placement
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) (DDP) where the hardware handles the expensive byte touching operations, such
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) as CRC computation and verification, and direct DMA to the final host memory
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) destination:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) - iSCSI PDU digest generation and verification
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) On transmitting, Chelsio S3 h/w computes and inserts the Header and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) Data digest into the PDUs.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) On receiving, Chelsio S3 h/w computes and verifies the Header and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) Data digest of the PDUs.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) - Direct Data Placement (DDP)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) S3 h/w can directly place the iSCSI Data-In or Data-Out PDU's
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) payload into pre-posted final destination host-memory buffers based
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) on the Initiator Task Tag (ITT) in Data-In or Target Task Tag (TTT)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) in Data-Out PDUs.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) - PDU Transmit and Recovery
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) On transmitting, S3 h/w accepts the complete PDU (header + data)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) from the host driver, computes and inserts the digests, decomposes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) the PDU into multiple TCP segments if necessary, and transmit all
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) the TCP segments onto the wire. It handles TCP retransmission if
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) needed.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) On receiving, S3 h/w recovers the iSCSI PDU by reassembling TCP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) segments, separating the header and data, calculating and verifying
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) the digests, then forwarding the header to the host. The payload data,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) if possible, will be directly placed into the pre-posted host DDP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) buffer. Otherwise, the payload data will be sent to the host too.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) The cxgb3i driver interfaces with open-iscsi initiator and provides the iSCSI
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) acceleration through Chelsio hardware wherever applicable.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) Using the cxgb3i Driver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) The following steps need to be taken to accelerates the open-iscsi initiator:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) 1. Load the cxgb3i driver: "modprobe cxgb3i"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) The cxgb3i module registers a new transport class "cxgb3i" with open-iscsi.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) * in the case of recompiling the kernel, the cxgb3i selection is located at::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) Device Drivers
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) SCSI device support --->
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) [*] SCSI low-level drivers --->
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) <M> Chelsio S3xx iSCSI support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) 2. Create an interface file located under /etc/iscsi/ifaces/ for the new
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) transport class "cxgb3i".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) The content of the file should be in the following format::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) iface.transport_name = cxgb3i
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) iface.net_ifacename = <ethX>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) iface.ipaddress = <iscsi ip address>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) * if iface.ipaddress is specified, <iscsi ip address> needs to be either the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) same as the ethX's ip address or an address on the same subnet. Make
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) sure the ip address is unique in the network.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) 3. edit /etc/iscsi/iscsid.conf
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) The default setting for MaxRecvDataSegmentLength (131072) is too big;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) replace with a value no bigger than 15360 (for example 8192)::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) node.conn[0].iscsi.MaxRecvDataSegmentLength = 8192
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) * The login would fail for a normal session if MaxRecvDataSegmentLength is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) too big. A error message in the format of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) "cxgb3i: ERR! MaxRecvSegmentLength <X> too big. Need to be <= <Y>."
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) would be logged to dmesg.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) 4. To direct open-iscsi traffic to go through cxgb3i's accelerated path,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) "-I <iface file name>" option needs to be specified with most of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) iscsiadm command. <iface file name> is the transport interface file created
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) in step 2.
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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