1Introduction 2============ 3 4libmthca is a userspace driver for Mellanox InfiniBand HCAs. It works 5as a plug-in module for libibverbs that allows programs to use 6Mellanox hardware directly from userspace. See the libibverbs package 7for more information. 8 9Using libmthca 10============== 11 12libmthca will be loaded and used automatically by programs linked with 13libibverbs. The ib_mthca kernel module must be loaded for HCA devices 14to be detected and used. 15 16Supported Hardware 17================== 18 19libmthca currently supports HCAs based on the following Mellanox chips: 20 21 MT23108 InfiniHost (PCI-X) 22 MT25208 InfiniHost III Ex (PCI Express) 23 MT25204 InfiniHost III Lx (PCI Express) 24 25Both non-DDR and DDR HCAs are supported, and the MT25208 is supported 26with both MT23108-compatible and native MemFree firmware. 27 28Valgrind Support 29================ 30 31When running applications that use libibverbs under the Valgrind 32memory-checking debugger, Valgrind will falsely report "read from 33uninitialized" for memory that was initialized by the kernel drivers 34or HCA hardware. Specifically, Valgrind cannot see when kernel 35drivers or HCA hardware write to userspace memory, so when the process 36reads from that memory, Valgrind incorrectly assumes that the memory 37contents are uninitialized, and therefore raises a warning. 38 39libmthca can be built with specific support for the Valgrind 40memory-checking debugger by specifying the --with-valgrind command 41line argument to configure. This flag enables code in libibverbs to 42tell Valgrind "this memory may look uninitialized, but it's really 43OK," which therefore suppresses the incorrect "read from 44uninitialized" warnings. This code adds trivial overhead to the 45critical performance path, so it is disabled by default. The intent 46is that production users can use a "normal" build of libmthca and 47developers can use the "valgrind debug" build by simply switching 48their OPENIB_DRIVER_PATH environment variables. 49 50Libmthca needs some header files from Valgrind in order to compile 51this support; it is important to use the header files from the same 52version of Valgrind that will be used at run time. You may need to 53specify the directory where Valgrind's header files are installed as 54an argument to --with-valgrind. For example 55 56 ./configure --with-valgrind=/opt/valgrind 57 58will make the libmthca build look for valgrind headers in 59/opt/valgrind/include 60