> -----Original Message-----
> From: Auld, Matthew <matthew.auld@xxxxxxxxx>
> Sent: Monday, September 26, 2022 9:52 PM
> To: Gupta, Anshuman <anshuman.gupta@xxxxxxxxx>; intel-
> gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: joonas.lahtinen@xxxxxxxxxxxxxxx; tvrtko.ursulin@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] drm/i915/dgfx: Grab wakeref at i915_ttm_unmap_virtual
>
> On 23/09/2022 15:31, Anshuman Gupta wrote:
> > We had already grabbed the rpm wakeref at obj destruction path, but it
> > also required to grab the wakeref when object moves.
> > When i915_gem_object_release_mmap_offset() gets called by
> > i915_ttm_move_notify(), it will release the mmap offset without
> > grabbing the wakeref. We want to avoid that therefore, grab the
> > wakreref at i915_ttm_unmap_virtual() accordingly.
> >
> > While doing that also changed the lmem_userfault_lock from mutex to
> > spinlock, as spinlock widely used for list.
> >
> > Also changed if (obj->userfault_count) to
> > GEM_BUG_ON(!obj->userfault_count).
> >
> > Fixes: ad74457a6b5a ("drm/i915/dgfx: Release mmap on rpm suspend")
> > Suggested-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> > Signed-off-by: Anshuman Gupta <anshuman.gupta@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_mman.c | 19 +++++-------
> > drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 39 ++++++++++++++++--------
> > drivers/gpu/drm/i915/gt/intel_gt.c | 11 ++++++-
> > drivers/gpu/drm/i915/gt/intel_gt_types.h | 2 +-
> > 4 files changed, 45 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> > b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> > index 73d9eda1d6b7..9da561c19a47 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> > @@ -557,11 +557,13 @@ void
> > i915_gem_object_runtime_pm_release_mmap_offset(struct
> > drm_i915_gem_object *
> >
> > drm_vma_node_unmap(&bo->base.vma_node, bdev->dev_mapping);
> >
> > - if (obj->userfault_count) {
> > - /* rpm wakeref provide exclusive access */
> > - list_del(&obj->userfault_link);
> > - obj->userfault_count = 0;
> > - }
> > + /*
> > + * We have exclusive access here via runtime suspend. All other callers
> > + * must first grab the rpm wakeref.
> > + */
> > + GEM_BUG_ON(!obj->userfault_count);
> > + list_del(&obj->userfault_link);
> > + obj->userfault_count = 0;
> > }
> >
> > void i915_gem_object_release_mmap_offset(struct drm_i915_gem_object
> > *obj) @@ -587,13 +589,6 @@ void
> i915_gem_object_release_mmap_offset(struct drm_i915_gem_object *obj)
> > spin_lock(&obj->mmo.lock);
> > }
> > spin_unlock(&obj->mmo.lock);
> > -
> > - if (obj->userfault_count) {
> > - mutex_lock(&to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > - list_del(&obj->userfault_link);
> > - mutex_unlock(&to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > - obj->userfault_count = 0;
> > - }
> > }
> >
> > static struct i915_mmap_offset *
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > index e3fc38dd5db0..0630eeca7316 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > @@ -509,18 +509,9 @@ static int i915_ttm_shrink(struct
> drm_i915_gem_object *obj, unsigned int flags)
> > static void i915_ttm_delete_mem_notify(struct ttm_buffer_object *bo)
> > {
> > struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
> > - intel_wakeref_t wakeref = 0;
> >
> > if (bo->resource && likely(obj)) {
> > - /* ttm_bo_release() already has dma_resv_lock */
> > - if (i915_ttm_cpu_maps_iomem(bo->resource))
> > - wakeref = intel_runtime_pm_get(&to_i915(obj-
> >base.dev)->runtime_pm);
> > -
> > __i915_gem_object_pages_fini(obj);
> > -
> > - if (wakeref)
> > - intel_runtime_pm_put(&to_i915(obj->base.dev)-
> >runtime_pm, wakeref);
> > -
> > i915_ttm_free_cached_io_rsgt(obj);
> > }
> > }
> > @@ -1052,12 +1043,15 @@ static vm_fault_t vm_fault_ttm(struct vm_fault
> *vmf)
> > if (ret == VM_FAULT_RETRY && !(vmf->flags &
> FAULT_FLAG_RETRY_NOWAIT))
> > goto out_rpm;
> >
> > - /* ttm_bo_vm_reserve() already has dma_resv_lock */
> > + /*
> > + * ttm_bo_vm_reserve() already has dma_resv_lock.
> > + * userfault_count is protected by dma_resv lock and rpm wakeref.
> > + */
> > if (ret == VM_FAULT_NOPAGE && wakeref && !obj->userfault_count) {
> > obj->userfault_count = 1;
> > - mutex_lock(&to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > + spin_lock(to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > list_add(&obj->userfault_link, &to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_list);
> > - mutex_unlock(&to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > + spin_unlock(to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > }
> >
> > if (wakeref & CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND)
> > @@ -1123,7 +1117,28 @@ static u64 i915_ttm_mmap_offset(struct
> > drm_i915_gem_object *obj)
> >
> > static void i915_ttm_unmap_virtual(struct drm_i915_gem_object *obj)
> > {
> > + struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
> > + intel_wakeref_t wakeref = 0;
> > +
> > + assert_object_held_shared(obj);
> > +
> > + if (i915_ttm_cpu_maps_iomem(bo->resource)) {
> > + wakeref =
> > +intel_runtime_pm_get(&to_i915(obj->base.dev)->runtime_pm);
> > +
> > + /* userfault_count is protected by obj lock and rpm wakeref. */
> > + if (obj->userfault_count) {
> > + spin_lock(to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > + list_del(&obj->userfault_link);
> > + spin_unlock(to_gt(to_i915(obj->base.dev))-
> >lmem_userfault_lock);
> > + obj->userfault_count = 0;
> > + }
> > +
> > + }
> > +
> > ttm_bo_unmap_virtual(i915_gem_to_ttm(obj));
> > +
> > + if (wakeref)
> > + intel_runtime_pm_put(&to_i915(obj->base.dev)->runtime_pm,
> wakeref);
> > }
> >
> > static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c
> > b/drivers/gpu/drm/i915/gt/intel_gt.c
> > index b367cfff48d5..1e63432d97bb 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> > @@ -41,7 +41,7 @@ void intel_gt_common_init_early(struct intel_gt *gt)
> > spin_lock_init(gt->irq_lock);
> >
> > INIT_LIST_HEAD(>->lmem_userfault_list);
> > - mutex_init(>->lmem_userfault_lock);
> > + spin_lock_init(gt->lmem_userfault_lock);
> > INIT_LIST_HEAD(>->closed_vma);
> > spin_lock_init(>->closed_lock);
> >
> > @@ -71,6 +71,10 @@ int intel_root_gt_init_early(struct drm_i915_private
> *i915)
> > if (!gt->irq_lock)
> > return -ENOMEM;
> >
> > + gt->lmem_userfault_lock = drmm_kzalloc(&i915->drm, sizeof(*gt-
> >lmem_userfault_lock), GFP_KERNEL);
> > + if (!gt->lmem_userfault_lock)
> > + return -ENOMEM;
> > +
> > intel_gt_common_init_early(gt);
> >
> > return 0;
> > @@ -813,6 +817,11 @@ static int intel_gt_tile_setup(struct intel_gt *gt,
> phys_addr_t phys_addr)
> > gt->uncore = uncore;
> > gt->irq_lock = irq_lock;
> >
> > + gt->lmem_userfault_lock = drmm_kzalloc(>->i915->drm,
> > + sizeof(*gt-
> >lmem_userfault_lock), GFP_KERNEL);
> > + if (!gt->lmem_userfault_lock)
> > + return -ENOMEM;
> > +
> > intel_gt_common_init_early(gt);
> > }
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h
> > b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> > index 30003d68fd51..925775310b1e 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> > @@ -153,7 +153,7 @@ struct intel_gt {
> > * but instead has exclusive access by virtue of all other accesses
> requiring
> > * holding the runtime pm wakeref.
> > */
> > - struct mutex lmem_userfault_lock;
> > + spinlock_t *lmem_userfault_lock;
> > struct list_head lmem_userfault_list;
>
> It looks like there were some comments off list about this. It doesn't look like
> runtime pm is really per gt, so maybe just stick all this in i915? Or was there
> some other reason for putting this in gt?
Thanks for review,
Yes runtime pm is not per GT , i had kept inside gt to align with GTT mmap releasing implementation,
As there it was encapsulated inside git->ggtt.
Also userfault_wakeref is also encapsulated with in GT.
Shall I move all userfault_wakeref, lmem_userfault_lock and lmem_userfault_list to i915 ?
Thanks ,
Anshuman Gupta.
>
> >
> > struct list_head closed_vma;
