The current probe time ownership check for Soft Reserved memory based
solely on CXL window intersection is insufficient. dax_hmem probing is not
always guaranteed to run after CXL enumeration and region assembly, which
can lead to incorrect ownership decisions before the CXL stack has
finished publishing windows and assembling committed regions.
Introduce deferred ownership handling for Soft Reserved ranges that
intersect CXL windows. When such a range is encountered during the
initial dax_hmem probe, schedule deferred work to wait for the CXL stack
to complete enumeration and region assembly before deciding ownership.
Once the deferred work runs, evaluate each Soft Reserved range
individually: if a CXL region fully contains the range, skip it and let
dax_cxl bind. Otherwise, register it with dax_hmem. This per-range
ownership model avoids the need for CXL region teardown and
alloc_dax_region() resource exclusion prevents double claiming.
Introduce a boolean flag dax_hmem_initial_probe to live inside device.c
so it survives module reload. Ensure dax_cxl defers driver registration
until dax_hmem has completed ownership resolution. dax_cxl calls
dax_hmem_flush_work() before cxl_driver_register(), which both waits for
the deferred work to complete and creates a module symbol dependency that
forces dax_hmem.ko to load before dax_cxl.
Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20260322195343.206900-9-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Move hmem/ earlier in the dax Makefile so that hmem_init() runs before
dax_cxl.
In addition, defer registration of the dax_cxl driver to a workqueue
instead of using module_cxl_driver(). This ensures that dax_hmem has
an opportunity to initialize and register its deferred callback and make
ownership decisions before dax_cxl begins probing and claiming Soft
Reserved ranges.
Mark the dax_cxl driver as PROBE_PREFER_ASYNCHRONOUS so its probe runs
out of line from other synchronous probing avoiding ordering
dependencies while coordinating ownership decisions with dax_hmem.
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Tomasz Wolski <tomasz.wolski@fujitsu.com>
Link: https://patch.msgid.link/20260322195343.206900-6-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dax/hmem/dax_hmem.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dax/device_dax.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dax/kmem.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dax/dax_pmem.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dax/dax_cxl.o
Add all missing invocations of the MODULE_DESCRIPTION() macro.
[iweiny: edit descriptions]
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://patch.msgid.link/r/20240605-md-drivers-dax-v1-1-3d448f3368b4@quicinc.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Large amounts of memory managed by the kmem driver may come in via CXL,
and it is often desirable to have the memmap for this memory on the new
memory itself.
Enroll kmem-managed memory for memmap_on_memory semantics if the dax
region originates via CXL. For non-CXL dax regions, retain the existing
default behavior of hot adding without memmap_on_memory semantics.
Link: https://lkml.kernel.org/r/20231107-vv-kmem_memmap-v10-3-1253ec050ed0@intel.com
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Li Zhijian <lizhijian@fujitsu.com> [cxl.kmem and nvdimm.kmem]
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Fan Ni <fan.ni@samsung.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Now that free_dev_dax_id() internally manages the references it needs
the extra references taken by the dax_region drivers are not needed.
Reported-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/168577285161.1672036.8111253437794419696.stgit@dwillia2-xfh.jf.intel.com
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
While platform firmware takes some responsibility for mapping the RAM
capacity of CXL devices present at boot, the OS is responsible for
mapping the remainder and hot-added devices. Platform firmware is also
responsible for identifying the platform general purpose memory pool,
typically DDR attached DRAM, and arranging for the remainder to be 'Soft
Reserved'. That reservation allows the CXL subsystem to route the memory
to core-mm via memory-hotplug (dax_kmem), or leave it for dedicated
access (device-dax).
The new 'struct cxl_dax_region' object allows for a CXL memory resource
(region) to be published, but also allow for udev and module policy to
act on that event. It also prevents cxl_core.ko from having a module
loading dependency on any drivers/dax/ modules.
Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/167602003896.1924368.10335442077318970468.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
