[0/3] Break VM to rq reference loop

Message

Ramalingam C June 14, 2022, 6:43 p.m. UTC

The i915_request holds a reference to intel_context, which in
turn holds a reference on the VM. But the dma-resv update for
VM_BIND feature would require VM hold a reference to the
i915_request through dma-resv fences of VM_PRIVATE objects
(which share a per VM dma-resv object).

Thus, we have a circular reference pattern causing the VM
reference to never reach 0, hence VM is not destroyed.

Break this by reverting the below patch which is making the
i915_request to hold a reference on intel_context.
"drm/i915: Hold reference to intel_context over life of i915_request"

This means we can't access rq->engine in i915_fence_get_driver_name()
as user do not hold a reference on rq->engine here. So, instead
store required device private pointer in 'rq->i915' and use it.

Niranjana Vishwanathapura (2):
  drm/i915: Do not access rq->engine without a reference
  Revert "drm/i915: Hold reference to intel_context over life of
    i915_request"

Ramalingam C (1):
  drm/i915: Do not use reserved requests for virtual engines

 drivers/gpu/drm/i915/i915_request.c | 55 ++++++++++++++++++-----------
 drivers/gpu/drm/i915/i915_request.h |  2 ++
 2 files changed, 36 insertions(+), 21 deletions(-)