• Mitko Haralanov's avatar
    IB/hfi1: Rework fault injection machinery · a74d5307
    Mitko Haralanov authored
    The packet fault injection code present in the HFI1 driver had some
    issues which not only fragment the code but also created user
    confusion. Furthermore, it suffered from the following issues:
    
      1. The fault_packet method only worked for received packets. This
         meant that the only fault injection mode available for sent
         packets is fault_opcode, which did not allow for random packet
         drops on all egressing packets.
      2. The mask available for the fault_opcode mode did not really work
         due to the fact that the opcode values are not bits in a bitmask but
         rather sequential integer values. Creating a opcode/mask pair that
         would successfully capture a set of packets was nearly impossible.
      3. The code was fragmented and used too many debugfs entries to
         operate and control. This was confusing to users.
      4. It did not allow filtering fault injection on a per direction basis -
         egress vs. ingress.
    
    In order to improve or fix the above issues, the following changes have
    been made:
    
       1. The fault injection methods have been combined into a single fault
          injection facility. As such, the fault injection has been plugged
          into both the send and receive code paths. Regardless of method used
          the fault injection will operate on both egress and ingress packets.
       2. The type of fault injection - by packet or by opcode - is now controlled
          by changing the boolean value of the file "opcode_mode". When the value
          is set to True, fault injection is done by opcode. Otherwise, by
          packet.
       2. The masking ability has been removed in favor of a bitmap that holds
          opcodes of interest (one bit per opcode, a total of 256 bits). This
          works in tandem with the "opcode_mode" value. When the value of
          "opcode_mode" is False, this bitmap is ignored. When the value is
          True, the bitmap lists all opcodes to be considered for fault injection.
          By default, the bitmap is empty. When the user wants to filter by opcode,
          the user sets the corresponding bit in the bitmap by echo'ing the bit
          position into the 'opcodes' file. This gets around the issue that the set
          of opcodes does not lend itself to effective masks and allow for extremely
          fine-grained filtering by opcode.
       4. fault_packet and fault_opcode methods have been combined. Hence, there
          is only one debugfs directory controlling the entire operation of the
          fault injection machinery. This reduces the number of debugfs entries
          and provides a more unified user experience.
       5. A new control files - "direction" - is provided to allow the user to
          control the direction of packets, which are subject to fault injection.
       6. A new control file - "skip_usec" - is added that would allow the user
          to specify a "timeout" during which no fault injection will occur.
    
    In addition, the following bug fixes have been applied:
    
       1. The fault injection code has been split into its own header and source
          files. This was done to better organize the code and support conditional
          compilation without littering the code with #ifdef's.
       2. The method by which the TX PIO packets were being marked for drop
          conflicted with the way send contexts were being setup. As a result,
          the send context was repeatedly being reset.
       3. The fault injection only makes sense when the user can control it
          through the debugfs entries. However, a kernel configuration can
          enable fault injection but keep fault injection debugfs entries
          disabled. Therefore, it makes sense that the HFI fault injection
          code depends on both.
       4. Error suppression did not take into account the method by which PIO
          packets were being dropped. Therefore, even with error suppression
          turned on, errors would still be displayed to the screen. A larger
          enough packet drop percentage would case the kernel to crash because
          the driver would be stuck printing errors.
    Reviewed-by: default avatarDennis Dalessandro <dennis.dalessandro@intel.com>
    Reviewed-by: default avatarDon Hiatt <don.hiatt@intel.com>
    Reviewed-by: default avatarMike Marciniszyn <mike.marciniszyn@intel.com>
    Signed-off-by: default avatarMitko Haralanov <mitko.haralanov@intel.com>
    Signed-off-by: default avatarDennis Dalessandro <dennis.dalessandro@intel.com>
    Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
    a74d5307
Makefile 715 Bytes