kernel/git/stable/linux.git/tools/testing/selftests/dax, branch masterLinux kernel stable treehttps://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/atom?h=master2026-08-07T01:57:00+00:00selftests/dax: add dax/kmem hotplug sysfs regression test2026-08-07T01:57:00+00:00Gregory Pricegourry@gourry.net2026-07-12T15:45:04+00:00urn:sha1:249c5ee21a26867b3b165f59cc0f2de335bd35bb
Add a kselftest for the dax/kmem whole-device "state" sysfs attribute
(/sys/bus/dax/devices/daxX.Y/state), which transitions a kmem-backed
dax device between "unplugged", "online" and "online_movable".
The kselftest also includes a test to demonstrate the force-unbind
does not deadlock - but this is destructive (the dax device can never
be rebound), so it only runs when DAX_KMEM_TEST_UNBIND=1 is set.
Provisioning a devdax device and binding it to kmem needs daxctl/ndctl
out of scope for an in-tree selftest. As the test mutates a device's
memory, the operator opts in by naming it in DAX_KMEM_TEST_DEV (or
"auto" to pick the first kmem-bound device); it SKIPs when unset, when
no device is present, or when the memory cannot be freed to a baseline.
When a device is available it validates the interface contract:
- online / online_movable actually add memory (MemTotal grows),
- online is idempotent,
- switching between online types without unplug is rejected,
- unplug removes memory and the reported state is "unplugged"
- invalid input is rejected,
- unplug and unbind tolerate blocks toggled out-of-band through the
per-block memoryX/state interface.
One specific regression test:
online -> unplug -> online_movable -> unplug
Re-online must re-reserve per-range resources so subsequent unplug
actually offlines and removes instead of silently reporting success
while the memory stays online.
Link: https://lore.kernel.org/20260712154505.3564379-11-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta@amd.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>