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Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6: (104 commits) [SCSI] fcoe: fix configuration problems [SCSI] cxgb3i: fix select/depend problem [SCSI] fcoe: fix incorrect use of struct module [SCSI] cxgb3i: remove use of skb->sp [SCSI] cxgb3i: Add cxgb3i iSCSI driver. [SCSI] zfcp: Remove unnecessary warning message [SCSI] zfcp: Add support for unchained FSF requests [SCSI] zfcp: Remove busid macro [SCSI] zfcp: remove DID_DID flag [SCSI] zfcp: Simplify mask lookups for incoming RSCNs [SCSI] zfcp: Remove initial device data from zfcp_data [SCSI] zfcp: fix compile warning [SCSI] zfcp: Remove adapter list [SCSI] zfcp: Simplify SBAL allocation to fix sparse warnings [SCSI] zfcp: register with SCSI layer on ccw registration [SCSI] zfcp: Fix message line break [SCSI] qla2xxx: changes in multiq code [SCSI] eata: fix the data buffer accessors conversion regression [SCSI] ibmvfc: Improve async event handling [SCSI] lpfc : correct printk types on PPC compiles ...
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Chelsio S3 iSCSI Driver for Linux | ||
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Introduction | ||
============ | ||
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The Chelsio T3 ASIC based Adapters (S310, S320, S302, S304, Mezz cards, etc. | ||
series of products) supports iSCSI acceleration and iSCSI Direct Data Placement | ||
(DDP) where the hardware handles the expensive byte touching operations, such | ||
as CRC computation and verification, and direct DMA to the final host memory | ||
destination: | ||
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- iSCSI PDU digest generation and verification | ||
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On transmitting, Chelsio S3 h/w computes and inserts the Header and | ||
Data digest into the PDUs. | ||
On receiving, Chelsio S3 h/w computes and verifies the Header and | ||
Data digest of the PDUs. | ||
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- Direct Data Placement (DDP) | ||
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S3 h/w can directly place the iSCSI Data-In or Data-Out PDU's | ||
payload into pre-posted final destination host-memory buffers based | ||
on the Initiator Task Tag (ITT) in Data-In or Target Task Tag (TTT) | ||
in Data-Out PDUs. | ||
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- PDU Transmit and Recovery | ||
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On transmitting, S3 h/w accepts the complete PDU (header + data) | ||
from the host driver, computes and inserts the digests, decomposes | ||
the PDU into multiple TCP segments if necessary, and transmit all | ||
the TCP segments onto the wire. It handles TCP retransmission if | ||
needed. | ||
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On receving, S3 h/w recovers the iSCSI PDU by reassembling TCP | ||
segments, separating the header and data, calculating and verifying | ||
the digests, then forwards the header to the host. The payload data, | ||
if possible, will be directly placed into the pre-posted host DDP | ||
buffer. Otherwise, the payload data will be sent to the host too. | ||
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The cxgb3i driver interfaces with open-iscsi initiator and provides the iSCSI | ||
acceleration through Chelsio hardware wherever applicable. | ||
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Using the cxgb3i Driver | ||
======================= | ||
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The following steps need to be taken to accelerates the open-iscsi initiator: | ||
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1. Load the cxgb3i driver: "modprobe cxgb3i" | ||
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The cxgb3i module registers a new transport class "cxgb3i" with open-iscsi. | ||
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* in the case of recompiling the kernel, the cxgb3i selection is located at | ||
Device Drivers | ||
SCSI device support ---> | ||
[*] SCSI low-level drivers ---> | ||
<M> Chelsio S3xx iSCSI support | ||
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2. Create an interface file located under /etc/iscsi/ifaces/ for the new | ||
transport class "cxgb3i". | ||
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The content of the file should be in the following format: | ||
iface.transport_name = cxgb3i | ||
iface.net_ifacename = <ethX> | ||
iface.ipaddress = <iscsi ip address> | ||
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* if iface.ipaddress is specified, <iscsi ip address> needs to be either the | ||
same as the ethX's ip address or an address on the same subnet. Make | ||
sure the ip address is unique in the network. | ||
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3. edit /etc/iscsi/iscsid.conf | ||
The default setting for MaxRecvDataSegmentLength (131072) is too big, | ||
replace "node.conn[0].iscsi.MaxRecvDataSegmentLength" to be a value no | ||
bigger than 15360 (for example 8192): | ||
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node.conn[0].iscsi.MaxRecvDataSegmentLength = 8192 | ||
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* The login would fail for a normal session if MaxRecvDataSegmentLength is | ||
too big. A error message in the format of | ||
"cxgb3i: ERR! MaxRecvSegmentLength <X> too big. Need to be <= <Y>." | ||
would be logged to dmesg. | ||
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4. To direct open-iscsi traffic to go through cxgb3i's accelerated path, | ||
"-I <iface file name>" option needs to be specified with most of the | ||
iscsiadm command. <iface file name> is the transport interface file created | ||
in step 2. |
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