[Mesa-dev] [PATCH v4 0/3] GEM BO padding to find OOB buffer writes

[kevin.rogovin at intel.com]

From: Kevin Rogovin <kevin.rogovin at intel.com>

This patch series adds a new debug option to pad each GEM BO allocated
by the brw_bufmgr with (weak) pseudo-random noise values which are then
checked after each batchbuffer dispatch to the kernel. This can be quite
valuable to find diffucult to track down heisenberg style bugs.

A possible follow-up series would be to write to stderr (or another
logging mechanism) if the OOB write is to a GEM BO that backs a GL
buffer object; that features would be quite useful for application
developers.

v4:
 Change debug macro name value to DEBUG_CHECK_OOB.
 (suggested/requested by Jason Ekstrand)

 Use map as well when filling the noise values to make code style more
 consistent.
 (suggested/requested by Jason Ekstrand)

v3:
 Change from using pread to mapping buffer padding on checking noise
 padding.
 (spawned from Chris Wilson feedback)

 Use gen_invalidate_range() to make sure values read are correct.
 (suggested/requested by Chris Wilson)

 Add comment to declaration of brw_bo_padding_is_good() indicating
 that one needs to wait for the GPU to finish the rendering of the
 contents of the batchbuffer that uses the GEM BO before calling
 brw_bo_padding_is_good().
 (spawned from Chris Wilson feedback)

 Call brw_bo_wait_rendering() when DEBUG_OUT_OF_BOUND_CHK bit
 is up before using brw_bo_padding_is_good().
 (spawned from Chris Wilson feedback)

v2:
 Change from using rand() to using internal generating function
 (requested/suggested by Jason Ekstrand)

 Avoid having extra pointers in brw_bo struct via using the internal
 function and allocating buffer for pread at brw_bo_padding_is_good()
 (requested/suggested by Jason Ekstrand)

 Comments indicating that pread ioctl will do the required waiting
 for GPU commands to finish

Kevin Rogovin (3):
  intel/common:add debug flag for adding and checking padding on BO's
  i965: add noise padding to buffer object and function to check if
    noise is correct
  i965: if DEBUG_CHECK_OOB is up, check that noise padding for each bo
    used in batchbuffer is correct

 src/intel/common/gen_debug.c                  |   1 +
 src/intel/common/gen_debug.h                  |   1 +
 src/mesa/drivers/dri/i965/brw_bufmgr.c        | 101 +++++++++++++++++++++++++-
 src/mesa/drivers/dri/i965/brw_bufmgr.h        |  13 ++++
 src/mesa/drivers/dri/i965/intel_batchbuffer.c |  22 +++++-
 5 files changed, 136 insertions(+), 2 deletions(-)

-- 
2.16.1