linux/drivers/cxl
Dan Williams 19398821b2 cxl/pmem: Fix nvdimm unregistration when cxl_pmem driver is absent
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:
     <TASK>
     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: cb9cfff82f ("cxl/acpi: Simplify cxl_nvdimm_bridge probing")
Reported-by: Gregory Price <gregory.price@memverge.com>
Debugged-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/167426077263.3955046.9695309346988027311.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2023-01-25 15:35:26 -08:00
..
core cxl/pmem: Fix nvdimm unregistration when cxl_pmem driver is absent 2023-01-25 15:35:26 -08:00
acpi.c cxl/pmem: Fix nvdimm unregistration when cxl_pmem driver is absent 2023-01-25 15:35:26 -08:00
cxl.h cxl: update names for interleave ways conversion macros 2022-12-05 18:17:16 -08:00
cxlmem.h cxl/mbox: Add variable output size validation for internal commands 2022-12-06 14:36:02 -08:00
cxlpci.h cxl/core/regs: Make cxl_map_{component, device}_regs() device generic 2022-12-03 13:40:16 -08:00
Kconfig cxl/region: Manage CPU caches relative to DPA invalidation events 2022-12-03 00:03:57 -08:00
Makefile cxl/pmem: Introduce nvdimm_security_ops with ->get_flags() operation 2022-11-30 16:30:47 -08:00
mem.c cxl/port: Add RCD endpoint port enumeration 2022-12-05 10:32:26 -08:00
pci.c cxl: fix cxl_report_and_clear() RAS UE addr mis-assignment 2023-01-09 12:55:54 -08:00
pmem.c cxl/pmem: Fix nvdimm unregistration when cxl_pmem driver is absent 2023-01-25 15:35:26 -08:00
port.c cxl/port: Read CDAT table 2022-07-19 15:38:05 -07:00
security.c cxl/mbox: Enable cxl_mbox_send_cmd() users to validate output size 2022-12-06 14:36:02 -08:00