diff options
Diffstat (limited to 'Documentation/infiniband')
| -rw-r--r-- | Documentation/infiniband/core_locking.txt | 114 | ||||
| -rw-r--r-- | Documentation/infiniband/ipoib.txt | 102 | ||||
| -rw-r--r-- | Documentation/infiniband/sysfs.txt | 66 | ||||
| -rw-r--r-- | Documentation/infiniband/user_mad.txt | 148 | ||||
| -rw-r--r-- | Documentation/infiniband/user_verbs.txt | 69 |
5 files changed, 499 insertions, 0 deletions
diff --git a/Documentation/infiniband/core_locking.txt b/Documentation/infiniband/core_locking.txt new file mode 100644 index 00000000..e1678542 --- /dev/null +++ b/Documentation/infiniband/core_locking.txt @@ -0,0 +1,114 @@ +INFINIBAND MIDLAYER LOCKING + + This guide is an attempt to make explicit the locking assumptions + made by the InfiniBand midlayer. It describes the requirements on + both low-level drivers that sit below the midlayer and upper level + protocols that use the midlayer. + +Sleeping and interrupt context + + With the following exceptions, a low-level driver implementation of + all of the methods in struct ib_device may sleep. The exceptions + are any methods from the list: + + create_ah + modify_ah + query_ah + destroy_ah + bind_mw + post_send + post_recv + poll_cq + req_notify_cq + map_phys_fmr + + which may not sleep and must be callable from any context. + + The corresponding functions exported to upper level protocol + consumers: + + ib_create_ah + ib_modify_ah + ib_query_ah + ib_destroy_ah + ib_bind_mw + ib_post_send + ib_post_recv + ib_req_notify_cq + ib_map_phys_fmr + + are therefore safe to call from any context. + + In addition, the function + + ib_dispatch_event + + used by low-level drivers to dispatch asynchronous events through + the midlayer is also safe to call from any context. + +Reentrancy + + All of the methods in struct ib_device exported by a low-level + driver must be fully reentrant. The low-level driver is required to + perform all synchronization necessary to maintain consistency, even + if multiple function calls using the same object are run + simultaneously. + + The IB midlayer does not perform any serialization of function calls. + + Because low-level drivers are reentrant, upper level protocol + consumers are not required to perform any serialization. However, + some serialization may be required to get sensible results. For + example, a consumer may safely call ib_poll_cq() on multiple CPUs + simultaneously. However, the ordering of the work completion + information between different calls of ib_poll_cq() is not defined. + +Callbacks + + A low-level driver must not perform a callback directly from the + same callchain as an ib_device method call. For example, it is not + allowed for a low-level driver to call a consumer's completion event + handler directly from its post_send method. Instead, the low-level + driver should defer this callback by, for example, scheduling a + tasklet to perform the callback. + + The low-level driver is responsible for ensuring that multiple + completion event handlers for the same CQ are not called + simultaneously. The driver must guarantee that only one CQ event + handler for a given CQ is running at a time. In other words, the + following situation is not allowed: + + CPU1 CPU2 + + low-level driver -> + consumer CQ event callback: + /* ... */ + ib_req_notify_cq(cq, ...); + low-level driver -> + /* ... */ consumer CQ event callback: + /* ... */ + return from CQ event handler + + The context in which completion event and asynchronous event + callbacks run is not defined. Depending on the low-level driver, it + may be process context, softirq context, or interrupt context. + Upper level protocol consumers may not sleep in a callback. + +Hot-plug + + A low-level driver announces that a device is ready for use by + consumers when it calls ib_register_device(), all initialization + must be complete before this call. The device must remain usable + until the driver's call to ib_unregister_device() has returned. + + A low-level driver must call ib_register_device() and + ib_unregister_device() from process context. It must not hold any + semaphores that could cause deadlock if a consumer calls back into + the driver across these calls. + + An upper level protocol consumer may begin using an IB device as + soon as the add method of its struct ib_client is called for that + device. A consumer must finish all cleanup and free all resources + relating to a device before returning from the remove method. + + A consumer is permitted to sleep in its add and remove methods. diff --git a/Documentation/infiniband/ipoib.txt b/Documentation/infiniband/ipoib.txt new file mode 100644 index 00000000..64eeb55d --- /dev/null +++ b/Documentation/infiniband/ipoib.txt @@ -0,0 +1,102 @@ +IP OVER INFINIBAND + + The ib_ipoib driver is an implementation of the IP over InfiniBand + protocol as specified by RFC 4391 and 4392, issued by the IETF ipoib + working group. It is a "native" implementation in the sense of + setting the interface type to ARPHRD_INFINIBAND and the hardware + address length to 20 (earlier proprietary implementations + masqueraded to the kernel as ethernet interfaces). + +Partitions and P_Keys + + When the IPoIB driver is loaded, it creates one interface for each + port using the P_Key at index 0. To create an interface with a + different P_Key, write the desired P_Key into the main interface's + /sys/class/net/<intf name>/create_child file. For example: + + echo 0x8001 > /sys/class/net/ib0/create_child + + This will create an interface named ib0.8001 with P_Key 0x8001. To + remove a subinterface, use the "delete_child" file: + + echo 0x8001 > /sys/class/net/ib0/delete_child + + The P_Key for any interface is given by the "pkey" file, and the + main interface for a subinterface is in "parent." + +Datagram vs Connected modes + + The IPoIB driver supports two modes of operation: datagram and + connected. The mode is set and read through an interface's + /sys/class/net/<intf name>/mode file. + + In datagram mode, the IB UD (Unreliable Datagram) transport is used + and so the interface MTU has is equal to the IB L2 MTU minus the + IPoIB encapsulation header (4 bytes). For example, in a typical IB + fabric with a 2K MTU, the IPoIB MTU will be 2048 - 4 = 2044 bytes. + + In connected mode, the IB RC (Reliable Connected) transport is used. + Connected mode takes advantage of the connected nature of the IB + transport and allows an MTU up to the maximal IP packet size of 64K, + which reduces the number of IP packets needed for handling large UDP + datagrams, TCP segments, etc and increases the performance for large + messages. + + In connected mode, the interface's UD QP is still used for multicast + and communication with peers that don't support connected mode. In + this case, RX emulation of ICMP PMTU packets is used to cause the + networking stack to use the smaller UD MTU for these neighbours. + +Stateless offloads + + If the IB HW supports IPoIB stateless offloads, IPoIB advertises + TCP/IP checksum and/or Large Send (LSO) offloading capability to the + network stack. + + Large Receive (LRO) offloading is also implemented and may be turned + on/off using ethtool calls. Currently LRO is supported only for + checksum offload capable devices. + + Stateless offloads are supported only in datagram mode. + +Interrupt moderation + + If the underlying IB device supports CQ event moderation, one can + use ethtool to set interrupt mitigation parameters and thus reduce + the overhead incurred by handling interrupts. The main code path of + IPoIB doesn't use events for TX completion signaling so only RX + moderation is supported. + +Debugging Information + + By compiling the IPoIB driver with CONFIG_INFINIBAND_IPOIB_DEBUG set + to 'y', tracing messages are compiled into the driver. They are + turned on by setting the module parameters debug_level and + mcast_debug_level to 1. These parameters can be controlled at + runtime through files in /sys/module/ib_ipoib/. + + CONFIG_INFINIBAND_IPOIB_DEBUG also enables files in the debugfs + virtual filesystem. By mounting this filesystem, for example with + + mount -t debugfs none /sys/kernel/debug + + it is possible to get statistics about multicast groups from the + files /sys/kernel/debug/ipoib/ib0_mcg and so on. + + The performance impact of this option is negligible, so it + is safe to enable this option with debug_level set to 0 for normal + operation. + + CONFIG_INFINIBAND_IPOIB_DEBUG_DATA enables even more debug output in + the data path when data_debug_level is set to 1. However, even with + the output disabled, enabling this configuration option will affect + performance, because it adds tests to the fast path. + +References + + Transmission of IP over InfiniBand (IPoIB) (RFC 4391) + http://ietf.org/rfc/rfc4391.txt + IP over InfiniBand (IPoIB) Architecture (RFC 4392) + http://ietf.org/rfc/rfc4392.txt + IP over InfiniBand: Connected Mode (RFC 4755) + http://ietf.org/rfc/rfc4755.txt diff --git a/Documentation/infiniband/sysfs.txt b/Documentation/infiniband/sysfs.txt new file mode 100644 index 00000000..ddd519b7 --- /dev/null +++ b/Documentation/infiniband/sysfs.txt @@ -0,0 +1,66 @@ +SYSFS FILES + + For each InfiniBand device, the InfiniBand drivers create the + following files under /sys/class/infiniband/<device name>: + + node_type - Node type (CA, switch or router) + node_guid - Node GUID + sys_image_guid - System image GUID + + In addition, there is a "ports" subdirectory, with one subdirectory + for each port. For example, if mthca0 is a 2-port HCA, there will + be two directories: + + /sys/class/infiniband/mthca0/ports/1 + /sys/class/infiniband/mthca0/ports/2 + + (A switch will only have a single "0" subdirectory for switch port + 0; no subdirectory is created for normal switch ports) + + In each port subdirectory, the following files are created: + + cap_mask - Port capability mask + lid - Port LID + lid_mask_count - Port LID mask count + rate - Port data rate (active width * active speed) + sm_lid - Subnet manager LID for port's subnet + sm_sl - Subnet manager SL for port's subnet + state - Port state (DOWN, INIT, ARMED, ACTIVE or ACTIVE_DEFER) + phys_state - Port physical state (Sleep, Polling, LinkUp, etc) + + There is also a "counters" subdirectory, with files + + VL15_dropped + excessive_buffer_overrun_errors + link_downed + link_error_recovery + local_link_integrity_errors + port_rcv_constraint_errors + port_rcv_data + port_rcv_errors + port_rcv_packets + port_rcv_remote_physical_errors + port_rcv_switch_relay_errors + port_xmit_constraint_errors + port_xmit_data + port_xmit_discards + port_xmit_packets + symbol_error + + Each of these files contains the corresponding value from the port's + Performance Management PortCounters attribute, as described in + section 16.1.3.5 of the InfiniBand Architecture Specification. + + The "pkeys" and "gids" subdirectories contain one file for each + entry in the port's P_Key or GID table respectively. For example, + ports/1/pkeys/10 contains the value at index 10 in port 1's P_Key + table. + +MTHCA + + The Mellanox HCA driver also creates the files: + + hw_rev - Hardware revision number + fw_ver - Firmware version + hca_type - HCA type: "MT23108", "MT25208 (MT23108 compat mode)", + or "MT25208" diff --git a/Documentation/infiniband/user_mad.txt b/Documentation/infiniband/user_mad.txt new file mode 100644 index 00000000..8a366959 --- /dev/null +++ b/Documentation/infiniband/user_mad.txt @@ -0,0 +1,148 @@ +USERSPACE MAD ACCESS + +Device files + + Each port of each InfiniBand device has a "umad" device and an + "issm" device attached. For example, a two-port HCA will have two + umad devices and two issm devices, while a switch will have one + device of each type (for switch port 0). + +Creating MAD agents + + A MAD agent can be created by filling in a struct ib_user_mad_reg_req + and then calling the IB_USER_MAD_REGISTER_AGENT ioctl on a file + descriptor for the appropriate device file. If the registration + request succeeds, a 32-bit id will be returned in the structure. + For example: + + struct ib_user_mad_reg_req req = { /* ... */ }; + ret = ioctl(fd, IB_USER_MAD_REGISTER_AGENT, (char *) &req); + if (!ret) + my_agent = req.id; + else + perror("agent register"); + + Agents can be unregistered with the IB_USER_MAD_UNREGISTER_AGENT + ioctl. Also, all agents registered through a file descriptor will + be unregistered when the descriptor is closed. + +Receiving MADs + + MADs are received using read(). The receive side now supports + RMPP. The buffer passed to read() must be at least one + struct ib_user_mad + 256 bytes. For example: + + If the buffer passed is not large enough to hold the received + MAD (RMPP), the errno is set to ENOSPC and the length of the + buffer needed is set in mad.length. + + Example for normal MAD (non RMPP) reads: + struct ib_user_mad *mad; + mad = malloc(sizeof *mad + 256); + ret = read(fd, mad, sizeof *mad + 256); + if (ret != sizeof mad + 256) { + perror("read"); + free(mad); + } + + Example for RMPP reads: + struct ib_user_mad *mad; + mad = malloc(sizeof *mad + 256); + ret = read(fd, mad, sizeof *mad + 256); + if (ret == -ENOSPC)) { + length = mad.length; + free(mad); + mad = malloc(sizeof *mad + length); + ret = read(fd, mad, sizeof *mad + length); + } + if (ret < 0) { + perror("read"); + free(mad); + } + + In addition to the actual MAD contents, the other struct ib_user_mad + fields will be filled in with information on the received MAD. For + example, the remote LID will be in mad.lid. + + If a send times out, a receive will be generated with mad.status set + to ETIMEDOUT. Otherwise when a MAD has been successfully received, + mad.status will be 0. + + poll()/select() may be used to wait until a MAD can be read. + +Sending MADs + + MADs are sent using write(). The agent ID for sending should be + filled into the id field of the MAD, the destination LID should be + filled into the lid field, and so on. The send side does support + RMPP so arbitrary length MAD can be sent. For example: + + struct ib_user_mad *mad; + + mad = malloc(sizeof *mad + mad_length); + + /* fill in mad->data */ + + mad->hdr.id = my_agent; /* req.id from agent registration */ + mad->hdr.lid = my_dest; /* in network byte order... */ + /* etc. */ + + ret = write(fd, &mad, sizeof *mad + mad_length); + if (ret != sizeof *mad + mad_length) + perror("write"); + +Transaction IDs + + Users of the umad devices can use the lower 32 bits of the + transaction ID field (that is, the least significant half of the + field in network byte order) in MADs being sent to match + request/response pairs. The upper 32 bits are reserved for use by + the kernel and will be overwritten before a MAD is sent. + +P_Key Index Handling + + The old ib_umad interface did not allow setting the P_Key index for + MADs that are sent and did not provide a way for obtaining the P_Key + index of received MADs. A new layout for struct ib_user_mad_hdr + with a pkey_index member has been defined; however, to preserve + binary compatibility with older applications, this new layout will + not be used unless the IB_USER_MAD_ENABLE_PKEY ioctl is called + before a file descriptor is used for anything else. + + In September 2008, the IB_USER_MAD_ABI_VERSION will be incremented + to 6, the new layout of struct ib_user_mad_hdr will be used by + default, and the IB_USER_MAD_ENABLE_PKEY ioctl will be removed. + +Setting IsSM Capability Bit + + To set the IsSM capability bit for a port, simply open the + corresponding issm device file. If the IsSM bit is already set, + then the open call will block until the bit is cleared (or return + immediately with errno set to EAGAIN if the O_NONBLOCK flag is + passed to open()). The IsSM bit will be cleared when the issm file + is closed. No read, write or other operations can be performed on + the issm file. + +/dev files + + To create the appropriate character device files automatically with + udev, a rule like + + KERNEL=="umad*", NAME="infiniband/%k" + KERNEL=="issm*", NAME="infiniband/%k" + + can be used. This will create device nodes named + + /dev/infiniband/umad0 + /dev/infiniband/issm0 + + for the first port, and so on. The InfiniBand device and port + associated with these devices can be determined from the files + + /sys/class/infiniband_mad/umad0/ibdev + /sys/class/infiniband_mad/umad0/port + + and + + /sys/class/infiniband_mad/issm0/ibdev + /sys/class/infiniband_mad/issm0/port diff --git a/Documentation/infiniband/user_verbs.txt b/Documentation/infiniband/user_verbs.txt new file mode 100644 index 00000000..e5092d69 --- /dev/null +++ b/Documentation/infiniband/user_verbs.txt @@ -0,0 +1,69 @@ +USERSPACE VERBS ACCESS + + The ib_uverbs module, built by enabling CONFIG_INFINIBAND_USER_VERBS, + enables direct userspace access to IB hardware via "verbs," as + described in chapter 11 of the InfiniBand Architecture Specification. + + To use the verbs, the libibverbs library, available from + http://www.openfabrics.org/, is required. libibverbs contains a + device-independent API for using the ib_uverbs interface. + libibverbs also requires appropriate device-dependent kernel and + userspace driver for your InfiniBand hardware. For example, to use + a Mellanox HCA, you will need the ib_mthca kernel module and the + libmthca userspace driver be installed. + +User-kernel communication + + Userspace communicates with the kernel for slow path, resource + management operations via the /dev/infiniband/uverbsN character + devices. Fast path operations are typically performed by writing + directly to hardware registers mmap()ed into userspace, with no + system call or context switch into the kernel. + + Commands are sent to the kernel via write()s on these device files. + The ABI is defined in drivers/infiniband/include/ib_user_verbs.h. + The structs for commands that require a response from the kernel + contain a 64-bit field used to pass a pointer to an output buffer. + Status is returned to userspace as the return value of the write() + system call. + +Resource management + + Since creation and destruction of all IB resources is done by + commands passed through a file descriptor, the kernel can keep track + of which resources are attached to a given userspace context. The + ib_uverbs module maintains idr tables that are used to translate + between kernel pointers and opaque userspace handles, so that kernel + pointers are never exposed to userspace and userspace cannot trick + the kernel into following a bogus pointer. + + This also allows the kernel to clean up when a process exits and + prevent one process from touching another process's resources. + +Memory pinning + + Direct userspace I/O requires that memory regions that are potential + I/O targets be kept resident at the same physical address. The + ib_uverbs module manages pinning and unpinning memory regions via + get_user_pages() and put_page() calls. It also accounts for the + amount of memory pinned in the process's locked_vm, and checks that + unprivileged processes do not exceed their RLIMIT_MEMLOCK limit. + + Pages that are pinned multiple times are counted each time they are + pinned, so the value of locked_vm may be an overestimate of the + number of pages pinned by a process. + +/dev files + + To create the appropriate character device files automatically with + udev, a rule like + + KERNEL=="uverbs*", NAME="infiniband/%k" + + can be used. This will create device nodes named + + /dev/infiniband/uverbs0 + + and so on. Since the InfiniBand userspace verbs should be safe for + use by non-privileged processes, it may be useful to add an + appropriate MODE or GROUP to the udev rule. |