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

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Overall Series Review

Subject: accel/amdxdna: Preserve user address when PASID is disabled
Author: Lizhi Hou <lizhi.hou@amd.com>
Patches: 3
Reviewed: 2026-06-04T13:24:31.255992

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This is a single-patch fix for the `accel/amdxdna` driver. The bug is clear: when PASID is disabled, `amdxdna_hmm_register()` returns early without setting `abo->mem.uva`, so it stays at `AMDXDNA_INVALID_ADDR` (its initialization value from `amdxdna_gem_create_obj()` at line 178). Later, `amdxdna_init_dev_bo()` calls `amdxdna_gem_uva(heap)` on each heap BO and checks:

```c
heap_addr = amdxdna_gem_uva(heap);
if (heap_addr == AMDXDNA_INVALID_ADDR) {
    XDNA_ERR(xdna, "Heap %d is not mapped", heap_id);
    return -EAGAIN;
}
```

This validation always fails in the no-PASID path because `uva` was never populated, even though the BO was successfully mapped. The fix is correct and minimal.

One minor observation: there is a behavioral asymmetry between the PASID-on and PASID-off paths after this patch that is worth noting but not blocking.

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