| Introduction |
| ============ |
| |
| libmthca is a userspace driver for Mellanox InfiniBand HCAs. It works |
| as a plug-in module for libibverbs that allows programs to use |
| Mellanox hardware directly from userspace. See the libibverbs package |
| for more information. |
| |
| Using libmthca |
| ============== |
| |
| libmthca will be loaded and used automatically by programs linked with |
| libibverbs. The ib_mthca kernel module must be loaded for HCA devices |
| to be detected and used. |
| |
| Supported Hardware |
| ================== |
| |
| libmthca currently supports HCAs based on the following Mellanox chips: |
| |
| MT23108 InfiniHost (PCI-X) |
| MT25208 InfiniHost III Ex (PCI Express) |
| MT25204 InfiniHost III Lx (PCI Express) |
| |
| Both non-DDR and DDR HCAs are supported, and the MT25208 is supported |
| with both MT23108-compatible and native MemFree firmware. |
| |
| Valgrind Support |
| ================ |
| |
| When running applications that use libibverbs under the Valgrind |
| memory-checking debugger, Valgrind will falsely report "read from |
| uninitialized" for memory that was initialized by the kernel drivers |
| or HCA hardware. Specifically, Valgrind cannot see when kernel |
| drivers or HCA hardware write to userspace memory, so when the process |
| reads from that memory, Valgrind incorrectly assumes that the memory |
| contents are uninitialized, and therefore raises a warning. |
| |
| libmthca can be built with specific support for the Valgrind |
| memory-checking debugger by specifying the --with-valgrind command |
| line argument to configure. This flag enables code in libibverbs to |
| tell Valgrind "this memory may look uninitialized, but it's really |
| OK," which therefore suppresses the incorrect "read from |
| uninitialized" warnings. This code adds trivial overhead to the |
| critical performance path, so it is disabled by default. The intent |
| is that production users can use a "normal" build of libmthca and |
| developers can use the "valgrind debug" build by simply switching |
| their OPENIB_DRIVER_PATH environment variables. |
| |
| Libmthca needs some header files from Valgrind in order to compile |
| this support; it is important to use the header files from the same |
| version of Valgrind that will be used at run time. You may need to |
| specify the directory where Valgrind's header files are installed as |
| an argument to --with-valgrind. For example |
| |
| ./configure --with-valgrind=/opt/valgrind |
| |
| will make the libmthca build look for valgrind headers in |
| /opt/valgrind/include |
