Claude review: accel/amdxdna: Preserve user address when PASID is disabled

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Correctness: The fix is correct.** Setting `abo->mem.uva = addr` before the early return ensures that `amdxdna_gem_uva()` returns a valid address for heap validation in `amdxdna_init_dev_bo()`, regardless of PASID state.

**Minor observations (non-blocking):**

1. **Cleanup asymmetry on munmap.** In the PASID-on path, `uva` is reset to `AMDXDNA_INVALID_ADDR` when the last umap entry is removed (`amdxdna_umap_release()` at `amdxdna_gem.c:322`). In the no-PASID path, no `mapp` is created and no entry is added to `umap_list`, so `uva` is never reset after munmap — it persists until the BO is freed. This means `amdxdna_gem_uva()` could return a stale address for an unmapped BO in the no-PASID case. In practice this is likely harmless because `amdxdna_obj_dma_addr()` uses `abo->mem.dma_addr` (not `uva`) when PASID is off, and heap validation would only occur during subsequent `amdxdna_init_dev_bo()` calls. But it's worth calling out.

2. **Repeated mmap behavior.** In the PASID-on path, `uva` is only set on the first mmap (guarded by `list_empty(&abo->mem.umap_list)` at line 389). With this patch, the no-PASID path sets `uva` on every mmap call unconditionally. For heap BOs this is fine since they're typically mmapped once, but it's a subtle behavioral difference.

3. **Locking.** The PASID-on path writes `uva` under `notifier_lock` (line 388–392). This patch writes `uva` without the lock. Since the no-PASID path doesn't manipulate `umap_list` and mmap is serialized by the mm's `mmap_lock`, this is safe in practice. The header comment (amdxdna_gem.h:33–36) already states `uva` can be accessed without `notifier_lock`.

**Verdict:** The patch is a clear bug fix with a correct Fixes tag. The asymmetries noted above are pre-existing design characteristics of the PASID-on vs PASID-off paths rather than issues introduced by this patch.

Reviewed-by tag warranted.

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