[PATCH 6.1 0265/1146] drm/i915/dgfx: Grab wakeref at i915_ttm_unmap_virtual

Greg Kroah-Hartman
2022-12-28T15:33:19Z

From: Anshuman Gupta <anshuman.gupta@intel.com>

[ Upstream commit 1cacd6894d5f4084f1581435e92d8a18d6721b25 ]

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 wakeref 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).

v2:
- Removed lmem_userfault_{list,lock} from intel_gt. [Matt Auld]

Fixes: ad74457a6b5a ("drm/i915/dgfx: Release mmap on rpm suspend")
Suggested-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221027092242.1476080-3-anshuman.gupta@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/i915/gem/i915_gem_mman.c | 19 +++++-------
drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 38 ++++++++++++++++--------
drivers/gpu/drm/i915/intel_runtime_pm.c | 2 +-
drivers/gpu/drm/i915/intel_runtime_pm.h | 2 +-
4 files changed, 35 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 fd29a9053582..e63329bc8065 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_i915(obj->base.dev)->runtime_pm.lmem_userfault_lock);
- list_del(&obj->userfault_link);
- mutex_unlock(&to_i915(obj->base.dev)->runtime_pm.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 d6b447ae0a16..be4c081e7e13 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 && !i915_ttm_is_ghost_object(bo)) {
- /* 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);
}
}
@@ -1056,12 +1047,15 @@ 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_i915(obj->base.dev)->runtime_pm.lmem_userfault_lock);
+ spin_lock(&to_i915(obj->base.dev)->runtime_pm.lmem_userfault_lock);
list_add(&obj->userfault_link, &to_i915(obj->base.dev)->runtime_pm.lmem_userfault_list);
- mutex_unlock(&to_i915(obj->base.dev)->runtime_pm.lmem_userfault_lock);
+ spin_unlock(&to_i915(obj->base.dev)->runtime_pm.lmem_userfault_lock);
}

if (wakeref & CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND)
@@ -1127,7 +1121,27 @@ 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_i915(obj->base.dev)->runtime_pm.lmem_userfault_lock);
+ list_del(&obj->userfault_link);
+ spin_unlock(&to_i915(obj->base.dev)->runtime_pm.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/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index bb74d4975cc8..129746713d07 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -655,6 +655,6 @@ void intel_runtime_pm_init_early(struct intel_runtime_pm *rpm)

init_intel_runtime_pm_wakeref(rpm);
INIT_LIST_HEAD(&rpm->lmem_userfault_list);
- mutex_init(&rpm->lmem_userfault_lock);
+ spin_lock_init(&rpm->lmem_userfault_lock);
intel_wakeref_auto_init(&rpm->userfault_wakeref, rpm);
}
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.h b/drivers/gpu/drm/i915/intel_runtime_pm.h
index 9f50f109aa11..98b8b28baaa1 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.h
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.h
@@ -64,7 +64,7 @@ struct intel_runtime_pm {
* 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;

/*
* Keep list of userfaulted gem obj, which require to release their
--
2.35.1