Re: [PATCH v2 2/4] drm/ttm: Clear all DMA mappings on demand

Am 26.08.21 um 19:27 schrieb Andrey Grodzovsky:

Used by drivers supporting hot unplug to handle all DMA IOMMU group related dependencies before the group is removed during device removal and we try to access it after free when last device pointer from user space is dropped.

Signed-off-by: Andrey Grodzovsky andrey.grodzovsky@amd.com

drivers/gpu/drm/ttm/ttm_device.c | 45 ++++++++++++++++++++++++++++++++ include/drm/ttm/ttm_device.h | 1 + 2 files changed, 46 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c index 5f31acec3ad7..ea50aba13743 100644 --- a/drivers/gpu/drm/ttm/ttm_device.c +++ b/drivers/gpu/drm/ttm/ttm_device.c @@ -245,3 +245,48 @@ void ttm_device_fini(struct ttm_device *bdev) ttm_global_release(); } EXPORT_SYMBOL(ttm_device_fini);

+void ttm_device_clear_dma_mappings(struct ttm_device *bdev) +{

• struct ttm_resource_manager *man;
• struct ttm_buffer_object *bo;
• unsigned int i, j;
• spin_lock(&bdev->lru_lock);
• for (i = TTM_PL_SYSTEM; i < TTM_NUM_MEM_TYPES; ++i) {

• man = ttm_manager_type(bdev, i);
  

• if (!man || !man->use_tt)
  

• 	continue;
  

• while (!list_empty(&man->pinned)) {
  

• 	bo = list_first_entry(&man->pinned, struct ttm_buffer_object, lru);
  

• 	/* Take ref against racing releases once lru_lock is unlocked */
  

• 	ttm_bo_get(bo);
  

This should probably use ttm_bo_get_unless_zero() since it is possible that the BO is already cleaning up in another thread.

• 	list_del_init(&bo->lru);
  

• 	spin_unlock(&bdev->lru_lock);
  

• 	if (bo->ttm)
  

• 		ttm_tt_destroy_common(bo->bdev, bo->ttm);
  

That needs to be ttm_tt_unpopulate() or otherwise we will mess up the statistics.

• 	ttm_bo_put(bo);
  

• 	spin_lock(&bdev->lru_lock);
  

• }
  

• for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
  

• 	while (!list_empty(&man->lru[j])) {
  

• 		bo = list_first_entry(&man->lru[j], struct ttm_buffer_object, lru);
  

• 		ttm_bo_get(bo);
  

Same here of course.

• 		list_del_init(&bo->lru);
  

• 		spin_unlock(&bdev->lru_lock);
  

• 		if (bo->ttm)
  

• 			ttm_tt_destroy_common(bo->bdev, bo->ttm);.
  

Same here.

Christian.

• 		ttm_bo_put(bo);
  

• 		spin_lock(&bdev->lru_lock);
  

• 	}
  

• }
  

• }
• spin_unlock(&bdev->lru_lock);

+} +EXPORT_SYMBOL(ttm_device_clear_dma_mappings); diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h index cd592f8e941b..d2837decb49a 100644 --- a/include/drm/ttm/ttm_device.h +++ b/include/drm/ttm/ttm_device.h @@ -298,5 +298,6 @@ int ttm_device_init(struct ttm_device *bdev, struct ttm_device_funcs *funcs, struct drm_vma_offset_manager *vma_manager, bool use_dma_alloc, bool use_dma32); void ttm_device_fini(struct ttm_device *bdev); +void ttm_device_clear_dma_mappings(struct ttm_device *bdev);

#endif