tree 50987e07348119f59db3ab33bf06642cf05da4f7
parent 6ba59ff4227927d3a8530fc2973b80e94b54d58f
author Li Ming <ming4.li@intel.com> 1718174663 +0800
committer Dave Jiang <dave.jiang@intel.com> 1718755010 -0700

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

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:
  <TASK>
  ? __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 <dan.j.williams@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Li Ming <ming4.li@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20240612064423.2567625-1-ming4.li@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>