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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>
This commit is contained in:
Dan Williams 2023-01-20 16:26:12 -08:00
parent 2ec1b17f74
commit 19398821b2
3 changed files with 29 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/cxl/acpi.c
View File

@ -736,4 +736,3 @@ module_exit(cxl_acpi_exit);
MODULE_LICENSE("GPL v2");
MODULE_IMPORT_NS(CXL);
MODULE_IMPORT_NS(ACPI);
MODULE_SOFTDEP("pre: cxl_pmem");

44
drivers/cxl/core/pmem.c
View File

@ -227,34 +227,16 @@ static struct cxl_nvdimm *cxl_nvdimm_alloc(struct cxl_nvdimm_bridge *cxl_nvb,
return cxl_nvd;
}
static void cxl_nvd_unregister(void *_cxl_nvd)
{
struct cxl_nvdimm *cxl_nvd = _cxl_nvd;
struct cxl_memdev *cxlmd = cxl_nvd->cxlmd;
struct cxl_nvdimm_bridge *cxl_nvb = cxlmd->cxl_nvb;
/*
* Either the bridge is in ->remove() context under the device_lock(),
* or cxlmd_release_nvdimm() is cancelling the bridge's release action
* for @cxl_nvd and doing it itself (while manually holding the bridge
* lock).
*/
device_lock_assert(&cxl_nvb->dev);
cxl_nvd->cxlmd = NULL;
cxlmd->cxl_nvd = NULL;
device_unregister(&cxl_nvd->dev);
}
static void cxlmd_release_nvdimm(void *_cxlmd)
{
struct cxl_memdev *cxlmd = _cxlmd;
struct cxl_nvdimm *cxl_nvd = cxlmd->cxl_nvd;
struct cxl_nvdimm_bridge *cxl_nvb = cxlmd->cxl_nvb;
device_lock(&cxl_nvb->dev);
if (cxlmd->cxl_nvd)
devm_release_action(&cxl_nvb->dev, cxl_nvd_unregister,
cxlmd->cxl_nvd);
device_unlock(&cxl_nvb->dev);
cxl_nvd->cxlmd = NULL;
cxlmd->cxl_nvd = NULL;
cxlmd->cxl_nvb = NULL;
device_unregister(&cxl_nvd->dev);
put_device(&cxl_nvb->dev);
}
@ -293,22 +275,6 @@ int devm_cxl_add_nvdimm(struct cxl_memdev *cxlmd)
dev_dbg(&cxlmd->dev, "register %s\n", dev_name(dev));
/*
* The two actions below arrange for @cxl_nvd to be deleted when either
* the top-level PMEM bridge goes down, or the endpoint device goes
* through ->remove().
*/
device_lock(&cxl_nvb->dev);
if (cxl_nvb->dev.driver)
rc = devm_add_action_or_reset(&cxl_nvb->dev, cxl_nvd_unregister,
cxl_nvd);
else
rc = -ENXIO;
device_unlock(&cxl_nvb->dev);
if (rc)
goto err_alloc;
/* @cxlmd carries a reference on @cxl_nvb until cxlmd_release_nvdimm */
return devm_add_action_or_reset(&cxlmd->dev, cxlmd_release_nvdimm, cxlmd);

24
drivers/cxl/pmem.c
View File

@ -225,11 +225,35 @@ static int cxl_pmem_ctl(struct nvdimm_bus_descriptor *nd_desc,
return cxl_pmem_nvdimm_ctl(nvdimm, cmd, buf, buf_len);
}
static int detach_nvdimm(struct device *dev, void *data)
{
struct cxl_nvdimm *cxl_nvd;
bool release = false;
if (!is_cxl_nvdimm(dev))
return 0;
device_lock(dev);
if (!dev->driver)
goto out;
cxl_nvd = to_cxl_nvdimm(dev);
if (cxl_nvd->cxlmd && cxl_nvd->cxlmd->cxl_nvb == data)
release = true;
out:
device_unlock(dev);
if (release)
device_release_driver(dev);
return 0;
}
static void unregister_nvdimm_bus(void *_cxl_nvb)
{
struct cxl_nvdimm_bridge *cxl_nvb = _cxl_nvb;
struct nvdimm_bus *nvdimm_bus = cxl_nvb->nvdimm_bus;
bus_for_each_dev(&cxl_bus_type, NULL, cxl_nvb, detach_nvdimm);
cxl_nvb->nvdimm_bus = NULL;
nvdimm_bus_unregister(nvdimm_bus);
}