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Sashiko AI review found 1 potential issue(s) to consider: > - [High] drm/xe: type confusion in xe_svm_devmem_lru_bump() due to unverified cast > -- > > commit 09484da3688fb659e04396330f11c6ca63c00b90 > Author: Himal Prasad Ghimiray > > drm/xe: Bump prefetch BO LRU via GPUSVM devmem callback > > This commit adds xe_svm_devmem_lru_bump() and sets it as the > drm_gpusvm_ctx.devmem_fn callback in the prefetch worker to move backing > BOs to the LRU tail during get_pages. > > > diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c > > index 6c3033fc4db73..7de6ed818d45e 100644 > > --- a/drivers/gpu/drm/xe/xe_svm.c > > +++ b/drivers/gpu/drm/xe/xe_svm.c > > [ ... ] > > > @@ -1612,6 +1613,25 @@ int xe_svm_range_get_pages(struct xe_vm *vm, struct xe_svm_range *range, > > return err; > > } > > > > +/** > > + * xe_svm_devmem_lru_bump() - Move a range's backing BO to the TTM LRU tail > > + * @devmem_allocation: The device-memory allocation backing the range's pages > > + * > > + * Intended as a &drm_gpusvm_ctx.devmem_fn. Runs under the GPUSVM notifier lock; > > + * the dma-resv trylock avoids inverting against eviction/shrinker, which take > > + * dma-resv before the notifier lock. A contended BO is simply skipped. > > + */ > > +void xe_svm_devmem_lru_bump(struct drm_pagemap_devmem *devmem_allocation) > > +{ > > + struct xe_bo *bo = to_xe_bo(devmem_allocation); Based on Sashiko feedback - we probably want a check here... if (devmem_allocation->ops != &dpagemap_devmem_ops) return; This would future-proof us if we ever start using SVM with device memory sharing on non-Xe devices while still sharing the same device_private_page_owner. At that point, we would likely need to rethink the LRU bumping, perhaps via a dpagemap_devmem_ops vfunc, but we would not immediately explode. Matt > > + > > + if (!dma_resv_trylock(bo->ttm.base.resv)) > > [Severity: High] > Does this cast safely handle generic device memory allocations? > > If userspace maps device memory from another DRM driver into the SVM address > space, hmm_range_fault() can return those foreign device pages. The drm_gpusvm > core will then loop over them in drm_gpusvm_walk_devmem() and invoke this > callback with the foreign driver's devmem_allocation. > > Since the generic struct drm_pagemap_devmem * is cast to a driver-specific > struct xe_bo * without verifying that the allocation actually belongs to the > xe driver, can this lead to a type confusion and invalid pointer dereference > on bo->ttm.base.resv? > > Unprivileged users mapping memory from multiple devices in the same process > could trigger a GPU fault or prefetch, making this a potential denial of > service vector. > > > + return; > > + > > + ttm_bo_move_to_lru_tail_unlocked(&bo->ttm); > > + dma_resv_unlock(bo->ttm.base.resv); > > +} > > + > > -- > Sashiko AI review · https://sashiko.dev/#/patchset/20260916112828.2528881-6-himal.prasad.ghimiray@intel.com?part=3