[PATCH v2 00/23] Fix xe_force_wake_get() failure handling

[Himal Prasad Ghimiray]

In case of xe_force_wake_get() call the refcount for domains
are incremented irrespective of failure or success, which can lead to
undefined behaviour: 
[1] subsequent forcewake call by callee function assumes domains are 
already awake, which might not be true. This shows perfectly balanced 
xe_force_wake_get/_put can also cause problem.

[2] The functions are using xe_force_wake_get() and return on failures.
In this scenario only the first caller returns and other functions will
always assume domains to be awake.

[1] func_a() {
	XE_WARN(xe_force_wake_get()) <---> fails but increments refcount

	func_b();

	XE_WARN(xe_force_wake_put());<---> decrements refcounts 
 }

    func_b() {
	if(xe_force_wake_get()) <---> succeeds due to refcount of caller
		return;

	does mmio_operations(); <---> Domain might not be awake

	xe_force_wake_put(); <---> decrement refcount
 }
  	
[2] func_a() {
	int err = xe_force_wake_get(); <---> returns if fails, inc refcount
	if (err)
		return;

	mmio_operations();

	xe_force_wake_put(); 
 }

    func_b() {
        if (xe_force_wake_get()) <---> succeeds due to refcnt of func_a()
              return;

        mmio_operations(); <---> Invalid accesses

        xe_force_wake_put(); <---> decrements refcount for func_b
 }

This series ensures refcount is not incremented in case of
xe_force_wake_get() failure and return mask of successfully refcount 
incremented domains.

For single domains (except XE_FORCEWAKE_ALL), the return value will be
0 on failure and doesn't need call to xe_force_wake_put()(if called,
call will return with check since input mask will be 0).
For XE_FORCEWAKE_ALL caller need to compare the returned mask with
XE_FORCEWAKE_ALL to confirm the success of call and need to explicitly
call xe_force_wake_put() with returned mask to put awaken domains to
sleep.
 

-v2 (Rodrigo, Badal)
- Dont put successfully awaken domains to sleep. Instead rely on _put to
  do that.
- Modified xe_force_wake_get() to return the refcount-incremented domain
  mask and xe_force_wake_put() uses this returned mask.

Cc: Badal Nilawar <badal.nilawar at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
Cc: Nirmoy Das <nirmoy.das at intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Cc: Ashutosh Dixit <ashutosh.dixit at intel.com>
Himal Prasad Ghimiray (23):
  drm/xe: Error handling in xe_force_wake_get()
  drm/xe: Modify xe_force_wake_put to handle _get returned mask
  drm/xe/device: Update handling of xe_force_wake_get return
  drm/xe/hdcp: Update handling of xe_force_wake_get return
  drm/xe/gsc: Update handling of xe_force_wake_get return
  drm/xe/gt: Update handling of xe_force_wake_get return
  drm/xe/xe_gt_idle: Update handling of xe_force_wake_get return
  drm/xe/devcoredump: Update handling of xe_force_wake_get return
  drm/xe/tests/mocs: Update xe_force_wake_get() return handling
  drm/xe/mocs: Update handling of xe_force_wake_get return
  drm/xe/xe_drm_client: Update handling of xe_force_wake_get return
  drm/xe/xe_gt_debugfs: Update handling of xe_force_wake_get return
  drm/xe/guc: Update handling of xe_force_wake_get return
  drm/xe/huc: Update handling of xe_force_wake_get return
  drm/xe/oa: Handle force_wake_get failure in xe_oa_stream_init()
  drm/xe/pat: Update handling of xe_force_wake_get return
  drm/xe/gt_tlb_invalidation_ggtt: Update handling of xe_force_wake_get
    return
  drm/xe/xe_reg_sr: Update handling of xe_force_wake_get return
  drm/xe/query: Update handling of xe_force_wake_get return
  drm/xe/vram: Update handling of xe_force_wake_get return
  drm/xe: forcewake debugfs open fails on xe_forcewake_get failure
  drm/xe: Ensure __must_check for xe_force_wake_get() return
  drm/xe: Change return type to void for xe_force_wake_put

 drivers/gpu/drm/xe/display/xe_hdcp_gsc.c    |   6 +-
 drivers/gpu/drm/xe/tests/xe_mocs.c          |  16 +--
 drivers/gpu/drm/xe/xe_debugfs.c             |  29 ++++-
 drivers/gpu/drm/xe/xe_devcoredump.c         |  13 ++-
 drivers/gpu/drm/xe/xe_device.c              |  25 +++--
 drivers/gpu/drm/xe/xe_drm_client.c          |   8 +-
 drivers/gpu/drm/xe/xe_force_wake.c          |  69 +++++++++---
 drivers/gpu/drm/xe/xe_force_wake.h          |   8 +-
 drivers/gpu/drm/xe/xe_gsc.c                 |  21 ++--
 drivers/gpu/drm/xe/xe_gsc_proxy.c           |   9 +-
 drivers/gpu/drm/xe/xe_gt.c                  | 113 +++++++++++---------
 drivers/gpu/drm/xe/xe_gt_debugfs.c          |  13 ++-
 drivers/gpu/drm/xe/xe_gt_idle.c             |  29 ++---
 drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c |   6 +-
 drivers/gpu/drm/xe/xe_guc.c                 |  14 +--
 drivers/gpu/drm/xe/xe_guc_pc.c              |  54 ++++++----
 drivers/gpu/drm/xe/xe_huc.c                 |   8 +-
 drivers/gpu/drm/xe/xe_mocs.c                |  10 +-
 drivers/gpu/drm/xe/xe_oa.c                  |  12 ++-
 drivers/gpu/drm/xe/xe_pat.c                 |  50 ++++-----
 drivers/gpu/drm/xe/xe_query.c               |   8 +-
 drivers/gpu/drm/xe/xe_reg_sr.c              |  24 ++---
 drivers/gpu/drm/xe/xe_vram.c                |  11 +-
 23 files changed, 335 insertions(+), 221 deletions(-)

-- 
2.34.1