[PATCH 0/5] cxl: Introduce devm_cxl_probe_mem() and fix region deletion

[Dan Williams <djbw@kernel.org>]

The devm_cxl_probe_mem() helper creates a memdev and retrieves a mapped
HPA range for the device. At present the retrieved region information is
expected to be established by platform firmware. A future update will
auto-establish a region if one is not already present. This arranges for a
simple CXL topology detach == Accelerator driver detach scheme.

Now, automatic region establishment on behalf of an accelerator driver
also requires automatic region teardown. The existing scheme of
triggering devm_release_action() of a cxl root device to destroy a
region is racy [1].  There is no path to coordinate multiple devres
actions, or conflicting devres actions, without using the
devm_remove_action_nowarn() workaround.

Instead, move final region cleanup responsibility to the root decoder
teardown path (devres action cxld_unregister()). Expand the root decoder
@range_lock, renamed @regions_lock, to coordinate region creation, sysfs
manageability, and deletion. The @regions_lock also prevents regions
from disappearing mid-auto-assembly.

Changes from the initial RFC [2]:
* tested with Dave's type2 cxl_test
* fix region remove by endpoints (Dave, Alejandro)
* fix user triggered region remove (Sungwoo)
* fix lifetime of the @attach ops (Alison, sashiko)
* hide @attach details inside the CXL core

[1]: http://lore.kernel.org/20260427032010.916681-2-iam@sung-woo.kim
[2]: http://lore.kernel.org/20260403210050.1058650-1-dan.j.williams@intel.com

Dan Williams (5):
  cxl/region: Block region delete during region creation
  cxl/region: Resolve region deletion races
  cxl/memdev: Pin parents for entire memdev lifetime
  cxl/memdev: Introduce cxl_class_memdev_type
  cxl/region: Introduce devm_cxl_probe_mem()

 drivers/cxl/core/core.h      |   2 +
 drivers/cxl/cxl.h            |   8 +-
 drivers/cxl/cxlmem.h         |  27 +++--
 include/cxl/cxl.h            |   3 +
 drivers/cxl/core/memdev.c    |  20 +++-
 drivers/cxl/core/port.c      |   7 +-
 drivers/cxl/core/region.c    | 194 ++++++++++++++++++++++++++++++-----
 drivers/cxl/mem.c            |  95 +++++++++++++----
 drivers/cxl/pci.c            |   2 +-
 tools/testing/cxl/test/mem.c |   2 +-
 10 files changed, 297 insertions(+), 63 deletions(-)


base-commit: 5d6919055dec134de3c40167a490f33c74c12581
-- 
2.53.0