linux-toradex.git/drivers/cxl/core/pmem.c, branch v6.12

cxl/mem: Fix no cxl_nvd during pmem region auto-assembling

2024-06-18T23:56:50+00:00

When CXL subsystem is auto-assembling a pmem region during cxl
endpoint port probing, always hit below calltrace.

BUG: kernel NULL pointer dereference, address: 0000000000000078
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
RIP: 0010:cxl_pmem_region_probe+0x22e/0x360 [cxl_pmem]
Call Trace:

? __die+0x24/0x70
? page_fault_oops+0x82/0x160
? do_user_addr_fault+0x65/0x6b0
? exc_page_fault+0x7d/0x170
? asm_exc_page_fault+0x26/0x30
? cxl_pmem_region_probe+0x22e/0x360 [cxl_pmem]
? cxl_pmem_region_probe+0x1ac/0x360 [cxl_pmem]
cxl_bus_probe+0x1b/0x60 [cxl_core]
really_probe+0x173/0x410
? __pfx___device_attach_driver+0x10/0x10
__driver_probe_device+0x80/0x170
driver_probe_device+0x1e/0x90
__device_attach_driver+0x90/0x120
bus_for_each_drv+0x84/0xe0
__device_attach+0xbc/0x1f0
bus_probe_device+0x90/0xa0
device_add+0x51c/0x710
devm_cxl_add_pmem_region+0x1b5/0x380 [cxl_core]
cxl_bus_probe+0x1b/0x60 [cxl_core]

The cxl_nvd of the memdev needs to be available during the pmem region
probe. Currently the cxl_nvd is registered after the endpoint port probe.
The endpoint probe, in the case of autoassembly of regions, can cause a
pmem region probe requiring the not yet available cxl_nvd. Adjust the
sequence so this dependency is met.

This requires adding a port parameter to cxl_find_nvdimm_bridge() that
can be used to query the ancestor root port. The endpoint port is not
yet available, but will share a common ancestor with its parent, so
start the query from there instead.

Fixes: f17b558d6663 ("cxl/pmem: Refactor nvdimm device registration, delete the workqueue")
Co-developed-by: Dan Williams
Signed-off-by: Dan Williams
Signed-off-by: Li Ming
Tested-by: Alison Schofield
Reviewed-by: Jonathan Cameron
Reviewed-by: Alison Schofield
Link: https://patch.msgid.link/20240612064423.2567625-1-ming4.li@intel.com
Signed-off-by: Dave Jiang

cxl: Refactor to use __free() for cxl_root allocation in cxl_find_nvdimm_bridge()

2024-01-05T22:36:29+00:00

Use scope-based resource management __free() macro to drop the open coded
put_device() in cxl_find_nvdimm_bridge().

Reviewed-by: Ira Weiny 
Signed-off-by: Dave Jiang 
Link: https://lore.kernel.org/r/170449247353.3779673.5963704495491343135.stgit@djiang5-mobl3
Signed-off-by: Dan Williams

cxl: Convert find_cxl_root() to return a 'struct cxl_root *'

2024-01-05T22:36:29+00:00

Commit 790815902ec6 ("cxl: Add support for _DSM Function for retrieving QTG ID")
introduced 'struct cxl_root', however all usages have been worked
indirectly through cxl_port. Refactor code such as find_cxl_root()
function to use 'struct cxl_root' directly.

Suggested-by: Dan Williams 
Reviewed-by: Ira Weiny 
Signed-off-by: Dave Jiang 
Link: https://lore.kernel.org/r/170449246044.3779673.13035770941393418591.stgit@djiang5-mobl3
Signed-off-by: Dan Williams

cxl/memdev: Formalize endpoint port linkage

2023-06-25T21:31:33+00:00

Move the endpoint port that the cxl_mem driver establishes from drvdata
to a first class attribute. This is in preparation for device-memory
drivers reusing the CXL core for memory region management. Those drivers
need a type-safe method to retrieve their CXL port linkage. Leave
drvdata for private usage of the cxl_mem driver not external consumers
of a 'struct cxl_memdev' object.

Reviewed-by: Fan Ni 
Reviewed-by: Jonathan Cameron 
Reviewed-by: Dave Jiang 
Link: https://lore.kernel.org/r/168679264292.3436160.3901392135863405807.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams

cxl/port: Fix find_cxl_root() for RCDs and simplify it

2023-04-04T22:34:34+00:00

The find_cxl_root() helper is used to lookup root decoders and other CXL
platform topology information for a given endpoint. It turns out that
for RCDs it has never worked. The result of find_cxl_root(&cxlmd->dev)
is always NULL for the RCH topology case because it expects to find a
cxl_port at the host-bridge. RCH topologies only have the root cxl_port
object with the host-bridge as a dport. While there are no reports of
this being a problem to date, by inspection region enumeration should
crash as a result of this problem, and it does in a local unit test for
this scenario.

However, an observation that ever since:

commit f17b558d6663 ("cxl/pmem: Refactor nvdimm device registration, delete the workqueue")

...all callers of find_cxl_root() occur after the memdev connection to
the port topology has been established. That means that find_cxl_root()
can be simplified to a walk of the endpoint port topology to the root.
Switch to that arrangement which also fixes the RCD bug.

Fixes: a32320b71f08 ("cxl/region: Add region autodiscovery")
Reviewed-by: Jonathan Cameron 
Reviewed-by: Dave Jiang 
Link: https://lore.kernel.org/r/168002857715.50647.344876437247313909.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams

cxl/pmem: Fix nvdimm unregistration when cxl_pmem driver is absent

2023-01-25T23:35:26+00:00

The cxl_pmem.ko module houses the driver for both cxl_nvdimm_bridge
objects and cxl_nvdimm objects. When the core creates a cxl_nvdimm it
arranges for it to be autoremoved when the bridge goes down. However, if
the bridge never initialized because the cxl_pmem.ko module never
loaded, it sets up a the following crash scenario:

    BUG: kernel NULL pointer dereference, address: 0000000000000478
    [..]
    RIP: 0010:cxl_nvdimm_probe+0x99/0x140 [cxl_pmem]
    [..]
    Call Trace:
     
     cxl_bus_probe+0x17/0x50 [cxl_core]
     really_probe+0xde/0x380
     __driver_probe_device+0x78/0x170
     driver_probe_device+0x1f/0x90
     __driver_attach+0xd2/0x1c0
     bus_for_each_dev+0x79/0xc0
     bus_add_driver+0x1b1/0x200
     driver_register+0x89/0xe0
     cxl_pmem_init+0x50/0xff0 [cxl_pmem]

It turns out the recent rework to simplify nvdimm probing obviated the
need to unregister cxl_nvdimm objects at cxl_nvdimm_bridge ->remove()
time. Leave the cxl_nvdimm device registered until the hosting
cxl_memdev departs. The alternative is that the cxl_memdev needs to be
reattached whenever the cxl_nvdimm_bridge attach state cycles, which is
awkward and unnecessary.

The only requirement is to make sure that when the cxl_nvdimm_bridge
goes away any dependent cxl_nvdimm objects are shutdown. Handle that in
unregister_nvdimm_bus().

With these registration entanglements removed there is no longer a need
to pre-load the cxl_pmem module in cxl_acpi.

Fixes: cb9cfff82f6a ("cxl/acpi: Simplify cxl_nvdimm_bridge probing")
Reported-by: Gregory Price 
Debugged-by: Jonathan Cameron 
Tested-by: Jonathan Cameron 
Reviewed-by: Jonathan Cameron 
Reviewed-by: Dave Jiang 
Link: https://lore.kernel.org/r/167426077263.3955046.9695309346988027311.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams

Merge branch 'for-6.2/cxl-security' into for-6.2/cxl

2022-12-05T20:30:38+00:00

Pick CXL PMEM security commands for v6.2. Resolve conflicts with the
removal of the cxl_pmem_wq.

cxl: add dimm_id support for __nvdimm_create()

2022-12-03T07:52:32+00:00

Set the cxlds->serial as the dimm_id to be fed to __nvdimm_create(). The
security code uses that as the key description for the security key of the
memory device. The nvdimm unlock code cannot find the respective key
without the dimm_id.

Reviewed-by: Jonathan Cameron 
Signed-off-by: Dave Jiang 
Link: https://lore.kernel.org/r/166863357043.80269.4337575149671383294.stgit@djiang5-desk3.ch.intel.com
Link: https://lore.kernel.org/r/166983620459.2734609.10175456773200251184.stgit@djiang5-desk3.ch.intel.com
Link: https://lore.kernel.org/r/166993219918.1995348.10786511454826454601.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams

cxl/pmem: Remove the cxl_pmem_wq and related infrastructure

2022-12-03T07:07:22+00:00

Now that cxl_nvdimm and cxl_pmem_region objects are torn down
sychronously with the removal of either the bridge, or an endpoint, the
cxl_pmem_wq infrastructure can be jettisoned.

Tested-by: Robert Richter 
Link: https://lore.kernel.org/r/166993042335.1882361.17022872468068436287.stgit@dwillia2-xfh.jf.intel.com
Reviewed-by: Jonathan Cameron 
Signed-off-by: Dan Williams

cxl/pmem: Refactor nvdimm device registration, delete the workqueue

2022-12-03T07:07:22+00:00

The three objects 'struct cxl_nvdimm_bridge', 'struct cxl_nvdimm', and
'struct cxl_pmem_region' manage CXL persistent memory resources. The
bridge represents base platform resources, the nvdimm represents one or
more endpoints, and the region is a collection of nvdimms that
contribute to an assembled address range.

Their relationship is such that a region is torn down if any component
endpoints are removed. All regions and endpoints are torn down if the
foundational bridge device goes down.

A workqueue was deployed to manage these interdependencies, but it is
difficult to reason about, and fragile. A recent attempt to take the CXL
root device lock in the cxl_mem driver was reported by lockdep as
colliding with the flush_work() in the cxl_pmem flows.

Instead of the workqueue, arrange for all pmem/nvdimm devices to be torn
down immediately and hierarchically. A similar change is made to both
the 'cxl_nvdimm' and 'cxl_pmem_region' objects. For bisect-ability both
changes are made in the same patch which unfortunately makes the patch
bigger than desired.

Arrange for cxl_memdev and cxl_region to register a cxl_nvdimm and
cxl_pmem_region as a devres release action of the bridge device.
Additionally, include a devres release action of the cxl_memdev or
cxl_region device that triggers the bridge's release action if an endpoint
exits before the bridge. I.e. this allows either unplugging the bridge,
or unplugging and endpoint to result in the same cleanup actions.

To keep the patch smaller the cleanup of the now defunct workqueue
infrastructure is saved for a follow-on patch.

Tested-by: Robert Richter 
Link: https://lore.kernel.org/r/166993041773.1882361.16444301376147207609.stgit@dwillia2-xfh.jf.intel.com
Reviewed-by: Jonathan Cameron 
Signed-off-by: Dan Williams