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to test and use this feature in the NTB transport layer. Also, bug fixes for the AMD and Switchtec drivers, as well as some general patches. -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEoE9b9c3U2JxX98mqbmZLrHqL0iMFAl0w0EwACgkQbmZLrHqL 0iNt4RAAiw2Cb2y5D36jI+lPl8xN2REk4x7b/FKFfLSzM/7Bu1okprrElKO6735r 0wRpyZS5lbYYr0QybzMrNfDMLYywFmA+C7GY7gQpR7GLYLb9chmvOmubfEbakHYI 4qKAWgaZt6PaiLQp76y3bFjUiBrd8KzVi5J891lDKvjzsGUjdNeFSlPlDbzTP8H9 +pBxnYn4G7MxVTebxjpOs6bQPO1sJZl4cyW40avTC1x+6bMlU1B361IhwtuabQH8 6rq6MQbaDzHTpuBZqZR8O+JxFzpffnGRu+smWPNQS2p95AewGIaDUsjZ6ph81rF1 mUxt/UJYP0RlIY+RQQ0Ie3cBUZ/I7wQzpFAXnqb8Nzba4tpc9ITX04hfnWKg6Kr0 sgj2Ro6I4TS3TSw6vquwvR2hn6+RZi06z/D0AXdUl+R3QxJXMyZygDDPDpTImZNy cnu+1Y7pdgjASXBvHKhM39+ynGLGze7xBIs6GO6TjJoVgZdMaW1/N/wsldYRc3Uf K0VSHowGHOyIV8d33oYWK2oSgWFrRCCanrCXIltNwl6NM05/b474L/8fiSnJ37PZ dJspdPdrut9W3018cRVHBhAX9csucbSa46FKz1Z0FEFjDJJzqy0isKDsoExBZqBH AqCnP548sbJF9+yOC475W36KMHBhyNvLS8XxD2J3DQpPDMRj//Y= =P1lR -----END PGP SIGNATURE----- Merge tag 'ntb-5.3' of git://github.com/jonmason/ntb Pull NTB updates from Jon Mason: "New feature to add support for NTB virtual MSI interrupts, the ability to test and use this feature in the NTB transport layer. Also, bug fixes for the AMD and Switchtec drivers, as well as some general patches" * tag 'ntb-5.3' of git://github.com/jonmason/ntb: (22 commits) NTB: Describe the ntb_msi_test client in the documentation. NTB: Add MSI interrupt support to ntb_transport NTB: Add ntb_msi_test support to ntb_test NTB: Introduce NTB MSI Test Client NTB: Introduce MSI library NTB: Rename ntb.c to support multiple source files in the module NTB: Introduce functions to calculate multi-port resource index NTB: Introduce helper functions to calculate logical port number PCI/switchtec: Add module parameter to request more interrupts PCI/MSI: Support allocating virtual MSI interrupts ntb_hw_switchtec: Fix setup MW with failure bug ntb_hw_switchtec: Skip unnecessary re-setup of shared memory window for crosslink case ntb_hw_switchtec: Remove redundant steps of switchtec_ntb_reinit_peer() function NTB: correct ntb_dev_ops and ntb_dev comment typos NTB: amd: Silence shift wrapping warning in amd_ntb_db_vector_mask() ntb_hw_switchtec: potential shift wrapping bug in switchtec_ntb_init_sndev() NTB: ntb_transport: Ensure qp->tx_mw_dma_addr is initaliazed NTB: ntb_hw_amd: set peer limit register NTB: ntb_perf: Clear stale values in doorbell and command SPAD register NTB: ntb_perf: Disable NTB link after clearing peer XLAT registers ...
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===========
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NTB Drivers
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===========
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NTB (Non-Transparent Bridge) is a type of PCI-Express bridge chip that connects
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the separate memory systems of two or more computers to the same PCI-Express
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fabric. Existing NTB hardware supports a common feature set: doorbell
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registers and memory translation windows, as well as non common features like
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scratchpad and message registers. Scratchpad registers are read-and-writable
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registers that are accessible from either side of the device, so that peers can
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exchange a small amount of information at a fixed address. Message registers can
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be utilized for the same purpose. Additionally they are provided with with
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special status bits to make sure the information isn't rewritten by another
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peer. Doorbell registers provide a way for peers to send interrupt events.
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Memory windows allow translated read and write access to the peer memory.
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NTB Core Driver (ntb)
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=====================
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The NTB core driver defines an api wrapping the common feature set, and allows
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clients interested in NTB features to discover NTB the devices supported by
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hardware drivers. The term "client" is used here to mean an upper layer
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component making use of the NTB api. The term "driver," or "hardware driver,"
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is used here to mean a driver for a specific vendor and model of NTB hardware.
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NTB Client Drivers
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==================
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NTB client drivers should register with the NTB core driver. After
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registering, the client probe and remove functions will be called appropriately
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as ntb hardware, or hardware drivers, are inserted and removed. The
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registration uses the Linux Device framework, so it should feel familiar to
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anyone who has written a pci driver.
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NTB Typical client driver implementation
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----------------------------------------
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Primary purpose of NTB is to share some peace of memory between at least two
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systems. So the NTB device features like Scratchpad/Message registers are
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mainly used to perform the proper memory window initialization. Typically
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there are two types of memory window interfaces supported by the NTB API:
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inbound translation configured on the local ntb port and outbound translation
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configured by the peer, on the peer ntb port. The first type is
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depicted on the next figure::
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Inbound translation:
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Memory: Local NTB Port: Peer NTB Port: Peer MMIO:
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____________
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| dma-mapped |-ntb_mw_set_trans(addr) |
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| memory | _v____________ | ______________
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| (addr) |<======| MW xlat addr |<====| MW base addr |<== memory-mapped IO
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|------------| |--------------| | |--------------|
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So typical scenario of the first type memory window initialization looks:
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1) allocate a memory region, 2) put translated address to NTB config,
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3) somehow notify a peer device of performed initialization, 4) peer device
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maps corresponding outbound memory window so to have access to the shared
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memory region.
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The second type of interface, that implies the shared windows being
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initialized by a peer device, is depicted on the figure::
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Outbound translation:
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Memory: Local NTB Port: Peer NTB Port: Peer MMIO:
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____________ ______________
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| dma-mapped | | | MW base addr |<== memory-mapped IO
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| memory | | |--------------|
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| (addr) |<===================| MW xlat addr |<-ntb_peer_mw_set_trans(addr)
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|------------| | |--------------|
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Typical scenario of the second type interface initialization would be:
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1) allocate a memory region, 2) somehow deliver a translated address to a peer
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device, 3) peer puts the translated address to NTB config, 4) peer device maps
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outbound memory window so to have access to the shared memory region.
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As one can see the described scenarios can be combined in one portable
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algorithm.
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Local device:
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1) Allocate memory for a shared window
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2) Initialize memory window by translated address of the allocated region
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(it may fail if local memory window initialization is unsupported)
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3) Send the translated address and memory window index to a peer device
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Peer device:
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1) Initialize memory window with retrieved address of the allocated
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by another device memory region (it may fail if peer memory window
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initialization is unsupported)
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2) Map outbound memory window
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In accordance with this scenario, the NTB Memory Window API can be used as
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follows:
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Local device:
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1) ntb_mw_count(pidx) - retrieve number of memory ranges, which can
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be allocated for memory windows between local device and peer device
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of port with specified index.
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2) ntb_get_align(pidx, midx) - retrieve parameters restricting the
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shared memory region alignment and size. Then memory can be properly
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allocated.
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3) Allocate physically contiguous memory region in compliance with
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restrictions retrieved in 2).
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4) ntb_mw_set_trans(pidx, midx) - try to set translation address of
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the memory window with specified index for the defined peer device
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(it may fail if local translated address setting is not supported)
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5) Send translated base address (usually together with memory window
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number) to the peer device using, for instance, scratchpad or message
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registers.
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Peer device:
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1) ntb_peer_mw_set_trans(pidx, midx) - try to set received from other
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device (related to pidx) translated address for specified memory
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window. It may fail if retrieved address, for instance, exceeds
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maximum possible address or isn't properly aligned.
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2) ntb_peer_mw_get_addr(widx) - retrieve MMIO address to map the memory
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window so to have an access to the shared memory.
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Also it is worth to note, that method ntb_mw_count(pidx) should return the
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same value as ntb_peer_mw_count() on the peer with port index - pidx.
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NTB Transport Client (ntb\_transport) and NTB Netdev (ntb\_netdev)
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------------------------------------------------------------------
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The primary client for NTB is the Transport client, used in tandem with NTB
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Netdev. These drivers function together to create a logical link to the peer,
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across the ntb, to exchange packets of network data. The Transport client
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establishes a logical link to the peer, and creates queue pairs to exchange
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messages and data. The NTB Netdev then creates an ethernet device using a
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Transport queue pair. Network data is copied between socket buffers and the
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Transport queue pair buffer. The Transport client may be used for other things
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besides Netdev, however no other applications have yet been written.
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NTB Ping Pong Test Client (ntb\_pingpong)
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-----------------------------------------
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The Ping Pong test client serves as a demonstration to exercise the doorbell
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and scratchpad registers of NTB hardware, and as an example simple NTB client.
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Ping Pong enables the link when started, waits for the NTB link to come up, and
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then proceeds to read and write the doorbell scratchpad registers of the NTB.
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The peers interrupt each other using a bit mask of doorbell bits, which is
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shifted by one in each round, to test the behavior of multiple doorbell bits
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and interrupt vectors. The Ping Pong driver also reads the first local
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scratchpad, and writes the value plus one to the first peer scratchpad, each
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round before writing the peer doorbell register.
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Module Parameters:
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* unsafe - Some hardware has known issues with scratchpad and doorbell
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registers. By default, Ping Pong will not attempt to exercise such
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hardware. You may override this behavior at your own risk by setting
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unsafe=1.
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* delay\_ms - Specify the delay between receiving a doorbell
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interrupt event and setting the peer doorbell register for the next
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round.
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* init\_db - Specify the doorbell bits to start new series of rounds. A new
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series begins once all the doorbell bits have been shifted out of
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range.
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* dyndbg - It is suggested to specify dyndbg=+p when loading this module, and
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then to observe debugging output on the console.
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NTB Tool Test Client (ntb\_tool)
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--------------------------------
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The Tool test client serves for debugging, primarily, ntb hardware and drivers.
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The Tool provides access through debugfs for reading, setting, and clearing the
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NTB doorbell, and reading and writing scratchpads.
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The Tool does not currently have any module parameters.
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Debugfs Files:
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* *debugfs*/ntb\_tool/*hw*/
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A directory in debugfs will be created for each
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NTB device probed by the tool. This directory is shortened to *hw*
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below.
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* *hw*/db
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This file is used to read, set, and clear the local doorbell. Not
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all operations may be supported by all hardware. To read the doorbell,
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read the file. To set the doorbell, write `s` followed by the bits to
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set (eg: `echo 's 0x0101' > db`). To clear the doorbell, write `c`
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followed by the bits to clear.
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* *hw*/mask
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This file is used to read, set, and clear the local doorbell mask.
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See *db* for details.
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* *hw*/peer\_db
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This file is used to read, set, and clear the peer doorbell.
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See *db* for details.
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* *hw*/peer\_mask
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This file is used to read, set, and clear the peer doorbell
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mask. See *db* for details.
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* *hw*/spad
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This file is used to read and write local scratchpads. To read
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the values of all scratchpads, read the file. To write values, write a
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series of pairs of scratchpad number and value
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(eg: `echo '4 0x123 7 0xabc' > spad`
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# to set scratchpads `4` and `7` to `0x123` and `0xabc`, respectively).
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* *hw*/peer\_spad
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This file is used to read and write peer scratchpads. See
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*spad* for details.
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NTB MSI Test Client (ntb\_msi\_test)
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------------------------------------
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The MSI test client serves to test and debug the MSI library which
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allows for passing MSI interrupts across NTB memory windows. The
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test client is interacted with through the debugfs filesystem:
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* *debugfs*/ntb\_tool/*hw*/
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A directory in debugfs will be created for each
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NTB device probed by the tool. This directory is shortened to *hw*
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below.
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* *hw*/port
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This file describes the local port number
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* *hw*/irq*_occurrences
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One occurrences file exists for each interrupt and, when read,
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returns the number of times the interrupt has been triggered.
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* *hw*/peer*/port
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This file describes the port number for each peer
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* *hw*/peer*/count
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This file describes the number of interrupts that can be
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triggered on each peer
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* *hw*/peer*/trigger
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Writing an interrupt number (any number less than the value
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specified in count) will trigger the interrupt on the
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specified peer. That peer's interrupt's occurrence file
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should be incremented.
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NTB Hardware Drivers
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====================
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NTB hardware drivers should register devices with the NTB core driver. After
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registering, clients probe and remove functions will be called.
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NTB Intel Hardware Driver (ntb\_hw\_intel)
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------------------------------------------
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The Intel hardware driver supports NTB on Xeon and Atom CPUs.
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Module Parameters:
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* b2b\_mw\_idx
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If the peer ntb is to be accessed via a memory window, then use
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this memory window to access the peer ntb. A value of zero or positive
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starts from the first mw idx, and a negative value starts from the last
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mw idx. Both sides MUST set the same value here! The default value is
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`-1`.
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* b2b\_mw\_share
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If the peer ntb is to be accessed via a memory window, and if
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the memory window is large enough, still allow the client to use the
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second half of the memory window for address translation to the peer.
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* xeon\_b2b\_usd\_bar2\_addr64
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If using B2B topology on Xeon hardware, use
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this 64 bit address on the bus between the NTB devices for the window
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at BAR2, on the upstream side of the link.
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* xeon\_b2b\_usd\_bar4\_addr64 - See *xeon\_b2b\_bar2\_addr64*.
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* xeon\_b2b\_usd\_bar4\_addr32 - See *xeon\_b2b\_bar2\_addr64*.
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* xeon\_b2b\_usd\_bar5\_addr32 - See *xeon\_b2b\_bar2\_addr64*.
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* xeon\_b2b\_dsd\_bar2\_addr64 - See *xeon\_b2b\_bar2\_addr64*.
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* xeon\_b2b\_dsd\_bar4\_addr64 - See *xeon\_b2b\_bar2\_addr64*.
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* xeon\_b2b\_dsd\_bar4\_addr32 - See *xeon\_b2b\_bar2\_addr64*.
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* xeon\_b2b\_dsd\_bar5\_addr32 - See *xeon\_b2b\_bar2\_addr64*.
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