[RFC 0/6] Default request/fence expiry + watchdog

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

"Watchdog" aka "restoring hangcheck" aka default request/fence expiry - first
post of a somewhat controversial feature so may be somewhat rough in commit
messages, commentary and implementation. So only RFC for now.

I parenthesise the "watchdog" becuase in classical sense watchdog would allow
userspace to ping it and so remain alive.

I parenthesise "restoring hangcheck" because this series, contrary to the old
hangcheck, is not looking at whether the workload is making any progress from
the kernel side either. (Althoguh disclaimer my memory may be leaky - Daniel
suspects old hangcheck had some stricter, more indiscriminatory, angles to it.
But apart from being prone to both false negatives and false positives I can't
remember that myself.)

Short version - ask is to fail any user submissions after a set time period. In
this RFC that time is ten seconds.

Time counts from the moment user submission is "runnable" (implicit and explicit
dependencies have been cleared) and keeps counting regardless of the GPU
contetion caused by other users of the system. So semantics are really a bit
weak but again, I understand this is really wanted by the DRM core.

As an attempt to compensate for this brutish nature, I proposed adding
extendable configurability via a context param as part of the series. That could
allow userspace to pick different semantics (always going more restrictive than
the system default) and so implement interesting things like long desired media
watchdog. Module trickyness of the implementation there.

Test-with: 20210312093329.1639502-1-tvrtko.ursulin at linux.intel.com
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>

Chris Wilson (1):
  drm/i915: Individual request cancellation

Tvrtko Ursulin (5):
  drm/i915: Restrict sentinel requests further
  drm/i915: Request watchdog infrastructure
  drm/i915: Allow userspace to configure the watchdog
  drm/i915: Fail too long user submissions by default
  drm/i915: Allow configuring default request expiry via modparam

 drivers/gpu/drm/i915/Kconfig.profile          |   8 +
 drivers/gpu/drm/i915/gem/i915_gem_context.c   |  92 ++++++
 .../gpu/drm/i915/gem/i915_gem_context_types.h |   4 +
 drivers/gpu/drm/i915/gt/intel_context_param.h |  11 +-
 drivers/gpu/drm/i915/gt/intel_context_types.h |   4 +
 .../gpu/drm/i915/gt/intel_engine_heartbeat.c  |   1 +
 .../drm/i915/gt/intel_execlists_submission.c  |  11 +-
 .../drm/i915/gt/intel_execlists_submission.h  |   2 +
 drivers/gpu/drm/i915/gt/intel_gt.c            |   3 +
 drivers/gpu/drm/i915/gt/intel_gt.h            |   2 +
 drivers/gpu/drm/i915/gt/intel_gt_requests.c   |  21 ++
 drivers/gpu/drm/i915/gt/intel_gt_types.h      |   7 +
 drivers/gpu/drm/i915/i915_params.c            |   5 +
 drivers/gpu/drm/i915/i915_params.h            |   1 +
 drivers/gpu/drm/i915/i915_request.c           | 129 +++++++-
 drivers/gpu/drm/i915/i915_request.h           |  12 +-
 drivers/gpu/drm/i915/selftests/i915_request.c | 275 ++++++++++++++++++
 include/uapi/drm/i915_drm.h                   |   5 +-
 18 files changed, 584 insertions(+), 9 deletions(-)

-- 
2.27.0