[PATCH v2 0/2] memblock tests: cover low-address allocations

[Tianyi Chen]

Model a low allocation limit within the dummy memory registered with
memblock, then exercise memblock_alloc_low() in both allocation directions.

Changes in v2, following Mike Rapoport's review:
- Clarify why the limit splits MEM_SIZE, the region registered by
  setup_memblock(), rather than the larger PHYS_MEM_SIZE malloc buffer.
- Explain why the malloc-backed base still needs alignment.
- Describe the boundary in terms of the last usable byte and clarify
  that reserving low memory succeeds; the following allocation fails.
- Update Assisted-by tags to the required tool:model format.

No allocator or test behavior changes from v1.

Validation with the existing Makefile and ASan/UBSan enabled:
- Default, NUMA=1, 32BIT_PHYS_ADDR_T=1, 32BIT_PHYS_ADDR_T=1 with NUMA=1,
  and MEMBLOCK_DEBUG=1 with NUMA=1 builds passed.
- Each configuration passed both ./main -v and ./main -v -m.
- A separate BUILD=32 run still hits the pre-existing
  memblock_free_near_max_check assertion in basic_api.c, also seen on
  the baseline. This is distinct from the passing 32-bit physical-address
  configuration above.

v1: https://lore.kernel.org/r/20260906144011.848898-1-hi@xxxxxxxxx
Review: https://lore.kernel.org/r/ap3LTQlKTpDbAEJZ@xxxxxxxxxx
Review: https://lore.kernel.org/r/ap3NJsaG10rLDVpd@xxxxxxxxxx

Tianyi Chen (2):
  memblock tests: model the low allocation limit within dummy memory
  memblock tests: cover allocations below the low address limit

 tools/testing/memblock/Makefile              |   3 +-
 tools/testing/memblock/README                |  14 +-
 tools/testing/memblock/TODO                  |   5 -
 tools/testing/memblock/asm/dma.h             |   6 +
 tools/testing/memblock/main.c                |   2 +
 tools/testing/memblock/tests/alloc_low_api.c | 148 +++++++++++++++++++
 tools/testing/memblock/tests/alloc_low_api.h |   9 ++
 tools/testing/memblock/tests/common.c        |   6 +
 8 files changed, 180 insertions(+), 13 deletions(-)
 delete mode 100644 tools/testing/memblock/TODO
 create mode 100644 tools/testing/memblock/tests/alloc_low_api.c
 create mode 100644 tools/testing/memblock/tests/alloc_low_api.h

-- 
2.55.0