[PATCH v2 1/3] drm/i915: Remove the vm open count

[Niranjana Vishwanathapura]

On Wed, Mar 02, 2022 at 11:21:58AM +0100, Thomas Hellström wrote:
>vms are not getting properly closed. Rather than fixing that,
>Remove the vm open count and instead rely on the vm refcount.
>
>The vm open count existed solely to break the strong references the
>vmas had on the vms. Now instead make those references weak and
>ensure vmas are destroyed when the vm is destroyed.
>
>Unfortunately if the vm destructor and the object destructor both
>wants to destroy a vma, that may lead to a race in that the vm
>destructor just unbinds the vma and leaves the actual vma destruction
>to the object destructor. However in order for the object destructor
>to ensure the vma is unbound it needs to grab the vm mutex. In order
>to keep the vm mutex alive until the object destructor is done with
>it, somewhat hackishly grab a vm_resv refcount that is released late
>in the vma destruction process, when the vm mutex is no longer needed.
>
>v2: Address review-comments from Niranjana
>- Clarify that the struct i915_address_space::skip_pte_rewrite is a hack and
>  should ideally be replaced in an upcoming patch.
>- Remove an unneeded continue in clear_vm_list and update comment.
>
>Co-developed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
>Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
>Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
>---
> drivers/gpu/drm/i915/display/intel_dpt.c      |  2 +-
> drivers/gpu/drm/i915/gem/i915_gem_context.c   | 29 ++-----
> .../gpu/drm/i915/gem/i915_gem_execbuffer.c    |  6 ++
> .../gpu/drm/i915/gem/selftests/mock_context.c |  5 +-
> drivers/gpu/drm/i915/gt/gen6_ppgtt.c          |  2 +-
> drivers/gpu/drm/i915/gt/intel_ggtt.c          | 30 +++----
> drivers/gpu/drm/i915/gt/intel_gtt.c           | 54 ++++++++----
> drivers/gpu/drm/i915/gt/intel_gtt.h           | 56 ++++--------
> drivers/gpu/drm/i915/gt/selftest_execlists.c  | 86 +++++++++----------
> drivers/gpu/drm/i915/i915_gem.c               |  6 +-
> drivers/gpu/drm/i915/i915_vma.c               | 55 ++++++++----
> drivers/gpu/drm/i915/i915_vma_resource.c      |  2 +-
> drivers/gpu/drm/i915/i915_vma_resource.h      |  6 ++
> drivers/gpu/drm/i915/i915_vma_types.h         |  7 ++
> drivers/gpu/drm/i915/selftests/i915_gem_gtt.c |  4 +-
> 15 files changed, 186 insertions(+), 164 deletions(-)
>

Looks good to me.
Reviewed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>