# DF-2091 — si_copy_dma u32 overflow truncates DMA for BOs >= 4GB

## Verdict
REPRODUCED (source-only confirmation). Bug confirmed by source tracing.

## Mechanism
si_copy_dma (si_dma.c:246): size_in_bytes=(num_gpu_pages << RADEON_GPU_PAGE_SHIFT) computed in u32. BO >= 2^20 GPU pages (4GB) wraps modulo 2^32. num_loops and ring reservation are then wrong.

## Fix
Change size_in_bytes to u64; keep cur_size_in_bytes as u32.

## Batch-build status
Applied with all 24 other fixes; kernel + modules compiled **rc=0, 0 errors, -Werror**.