From c3673464ebc004a3d82063cd41b9cf74d1b55db2 Mon Sep 17 00:00:00 2001 From: Karen Xie Date: Tue, 9 Dec 2008 14:15:32 -0800 Subject: [SCSI] cxgb3i: Add cxgb3i iSCSI driver. This patch implements the cxgb3i iscsi connection acceleration for the open-iscsi initiator. The cxgb3i driver offers the iscsi PDU based offload: - digest insertion and verification - payload direct-placement into host memory buffer. Signed-off-by: Karen Xie Signed-off-by: James Bottomley --- Documentation/scsi/cxgb3i.txt | 85 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 Documentation/scsi/cxgb3i.txt (limited to 'Documentation/scsi/cxgb3i.txt') diff --git a/Documentation/scsi/cxgb3i.txt b/Documentation/scsi/cxgb3i.txt new file mode 100644 index 000000000000..8141fa01978e --- /dev/null +++ b/Documentation/scsi/cxgb3i.txt @@ -0,0 +1,85 @@ +Chelsio S3 iSCSI Driver for Linux + +Introduction +============ + +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: + + - iSCSI PDU digest generation and verification + + 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. + + - Direct Data Placement (DDP) + + 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. + + - PDU Transmit and Recovery + + 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. + + 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. + +The cxgb3i driver interfaces with open-iscsi initiator and provides the iSCSI +acceleration through Chelsio hardware wherever applicable. + +Using the cxgb3i Driver +======================= + +The following steps need to be taken to accelerates the open-iscsi initiator: + +1. Load the cxgb3i driver: "modprobe cxgb3i" + + The cxgb3i module registers a new transport class "cxgb3i" with open-iscsi. + + * in the case of recompiling the kernel, the cxgb3i selection is located at + Device Drivers + SCSI device support ---> + [*] SCSI low-level drivers ---> + Chelsio S3xx iSCSI support + +2. Create an interface file located under /etc/iscsi/ifaces/ for the new + transport class "cxgb3i". + + The content of the file should be in the following format: + iface.transport_name = cxgb3i + iface.net_ifacename = + iface.ipaddress = + + * if iface.ipaddress is specified, 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. + +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): + + node.conn[0].iscsi.MaxRecvDataSegmentLength = 8192 + + * The login would fail for a normal session if MaxRecvDataSegmentLength is + too big. A error message in the format of + "cxgb3i: ERR! MaxRecvSegmentLength too big. Need to be <= ." + would be logged to dmesg. + +4. To direct open-iscsi traffic to go through cxgb3i's accelerated path, + "-I " option needs to be specified with most of the + iscsiadm command. is the transport interface file created + in step 2. -- cgit v1.2.3