Claude review: dmem: add amdgpu support and one more test

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

Overall Series Review

Subject: dmem: add amdgpu support and one more test
Author: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Patches: 16
Reviewed: 2026-05-16T12:42:31.479017

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This is an IGT (intel-gpu-tools) series, not a kernel series. It introduces a driver abstraction layer (`igt_dmem_driver`) to generalize the Xe-specific `xe_cgroups` dmem cgroup test so the same tests work across multiple GPU drivers. The series adds amdgpu support and a new `test_current` subtest that verifies cgroup `dmem.current`/`dmem.max` tracking.

The refactoring approach is sound: extract a vtable interface, port the existing Xe code, rename the test to be driver-agnostic, add amdgpu, then layer on improvements. The patch ordering is logical, and the series is well-decomposed.

**Key concerns:**
1. **Bug in patch 6** -- the max=0 assertion is inverted and will cause the test to fail on Xe (the primary target) while passing on amdgpu for the wrong reason.
2. **VA address leak in xe_dmem** -- `xe_ctx->addr` is never reset after `free_vram`, so the `test_current` subtest (which does multiple allocate/free cycles) will keep incrementing the bind address.
3. **amdgpu GTT fallback** weakens test coverage -- `fill_vram` with `err == 0` accepted means the eviction test may not exercise the intended code path on amdgpu at all.

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