[PATCH 0/9] dax/hmem: Add tests for the dax_hmem takeover capability

[Dan Williams <dan.j.williams@intel.com>]

Given all the cross subsystem dependencies needed to make this solution
work, it needs to have a unit test to keep it functional.

On the path to writing that, several fixes fell out, but not to Smita's
code, to mine. One use-after-free has been there since the original
automatic region assembly code.

Here is a preview of the core of the test I will submit to the cxl-cli project:

---
modprobe cxl_mock_mem && modprobe cxl_test hmem_test=1

dax=$(find_dax_cxl)
[[ "$dax" == "" ]] && err $LINENO
dax=$(find_dax_hmem)
[[ "$dax" != "" ]] && err $LINENO

unload

modprobe cxl_mock_mem && modprobe cxl_test fail_autoassemble hmem_test=1

dax=$(find_dax_cxl)
[[ "$dax" != "" ]] && err $LINENO
dax=$(find_dax_hmem)
[[ "$dax" == "" ]] && err $LINENO

unload
---

This builds on Smita's series [1] pushed out to for-7.1/dax-hmem in
cxl.git [2].

[1]: http://lore.kernel.org/20260322195343.206900-1-Smita.KoralahalliChannabasappa@amd.com
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/log/?h=for-7.1/dax-hmem

Dan Williams (9):
  cxl/region: Fix use-after-free from auto assembly failure
  dax/cxl: Fix HMEM dependencies
  cxl/region: Limit visibility of cxl_region_contains_resource()
  cxl/region: Constify cxl_region_resource_contains()
  dax/hmem: Reduce visibility of dax_cxl coordination symbols
  dax/hmem: Fix singleton confusion between dax_hmem_work and hmem
    devices
  dax/hmem: Parent dax_hmem devices
  tools/testing/cxl: Simulate auto-assembly failure
  tools/testing/cxl: Test dax_hmem takeover of CXL regions

 drivers/dax/Kconfig                |   6 +-
 drivers/cxl/cxl.h                  |  11 ++-
 drivers/dax/bus.h                  |  15 +++-
 include/cxl/cxl.h                  |  15 ----
 tools/testing/cxl/test/mock.h      |   8 ++
 drivers/cxl/core/region.c          |  68 +++++++++++++++--
 drivers/dax/hmem/device.c          |  28 ++++---
 drivers/dax/hmem/hmem.c            | 115 +++++++++++++++--------------
 tools/testing/cxl/test/cxl.c       |  66 +++++++++++++++++
 tools/testing/cxl/test/hmem_test.c |  47 ++++++++++++
 tools/testing/cxl/test/mem.c       |   3 +
 tools/testing/cxl/test/mock.c      |  50 +++++++++++++
 tools/testing/cxl/Kbuild           |   7 ++
 tools/testing/cxl/test/Kbuild      |   1 +
 14 files changed, 344 insertions(+), 96 deletions(-)
 delete mode 100644 include/cxl/cxl.h
 create mode 100644 tools/testing/cxl/test/hmem_test.c


base-commit: 51d2fa02c0e4b3b23c4484f2af9b6d65c35471e8
-- 
2.53.0