Hello Maarten Lankhorst,
This is a semi-automatic email about new static checker warnings.
The patch f6c466b84cfa: "drm/i915: Add support for moving fence
waiting" from Nov 22, 2021, leads to the following Smatch complaint:
drivers/gpu/drm/i915/i915_vma.c:1015 i915_vma_pin_ww()
error: we previously assumed 'vma->obj' could be null (see line 924)
drivers/gpu/drm/i915/i915_vma.c
923
924 moving = vma->obj ? i915_gem_object_get_moving_fence(vma->obj)
: NULL;
^^^^^^^^
The patch adds a check for NULL
925 if (flags & vma->vm->bind_async_flags || moving) {
926 /* lock VM */
927 err = i915_vm_lock_objects(vma->vm, ww);
928 if (err)
929 goto err_rpm;
930
931 work = i915_vma_work();
932 if (!work) {
933 err = -ENOMEM;
934 goto err_rpm;
935 }
936
937 work->vm = i915_vm_get(vma->vm);
938
939 dma_fence_work_chain(&work->base, moving);
940
941 /* Allocate enough page directories to used PTE */
942 if (vma->vm->allocate_va_range) {
943 err = i915_vm_alloc_pt_stash(vma->vm,
944 &work->stash,
945 vma->size);
946 if (err)
947 goto err_fence;
948
949 err = i915_vm_map_pt_stash(vma->vm,
&work->stash);
950 if (err)
951 goto err_fence;
952 }
953 }
954
955 /*
956 * Differentiate between user/kernel vma inside the
aliasing-ppgtt.
957 *
958 * We conflate the Global GTT with the user's vma when using the
959 * aliasing-ppgtt, but it is still vitally important to try and
960 * keep the use cases distinct. For example, userptr objects are
961 * not allowed inside the Global GTT as that will cause lock
962 * inversions when we have to evict them the mmu_notifier
callbacks -
963 * but they are allowed to be part of the user ppGTT which can
never
964 * be mapped. As such we try to give the distinct users of the
same
965 * mutex, distinct lockclasses [equivalent to how we keep
i915_ggtt
966 * and i915_ppgtt separate].
967 *
968 * NB this may cause us to mask real lock inversions -- while
the
969 * code is safe today, lockdep may not be able to spot future
970 * transgressions.
971 */
972 err = mutex_lock_interruptible_nested(&vma->vm->mutex,
973 !(flags & PIN_GLOBAL));
974 if (err)
975 goto err_fence;
976
977 /* No more allocations allowed now we hold vm->mutex */
978
979 if (unlikely(i915_vma_is_closed(vma))) {
980 err = -ENOENT;
981 goto err_unlock;
982 }
983
984 bound = atomic_read(&vma->flags);
985 if (unlikely(bound & I915_VMA_ERROR)) {
986 err = -ENOMEM;
987 goto err_unlock;
988 }
989
990 if (unlikely(!((bound + 1) & I915_VMA_PIN_MASK))) {
991 err = -EAGAIN; /* pins are meant to be fairly temporary
*/
992 goto err_unlock;
993 }
994
995 if (unlikely(!(flags & ~bound & I915_VMA_BIND_MASK))) {
996 __i915_vma_pin(vma);
997 goto err_unlock;
998 }
999
1000 err = i915_active_acquire(&vma->active);
1001 if (err)
1002 goto err_unlock;
1003
1004 if (!(bound & I915_VMA_BIND_MASK)) {
1005 err = i915_vma_insert(vma, size, alignment, flags);
1006 if (err)
1007 goto err_active;
1008
1009 if (i915_is_ggtt(vma->vm))
1010 __i915_vma_set_map_and_fenceable(vma);
1011 }
1012
1013 GEM_BUG_ON(!vma->pages);
1014 err = i915_vma_bind(vma,
1015 vma->obj->cache_level,
^^^^^^^^^^
This older code dereferences it without checking.
1016 flags, work);
1017 if (err)
regards,
dan carpenter
