A test of the form:
while true; do modprobe -r cxl_pmem; modprobe cxl_pmem; done
May lead to a crash signature of the form:
BUG: unable to handle page fault for address: ffffffffc0660030
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
[..]
Workqueue: cxl_pmem 0xffffffffc0660030
RIP: 0010:0xffffffffc0660030
Code: Unable to access opcode bytes at RIP 0xffffffffc0660006.
[..]
Call Trace:
? process_one_work+0x4ec/0x9c0
? pwq_dec_nr_in_flight+0x100/0x100
? rwlock_bug.part.0+0x60/0x60
? worker_thread+0x2eb/0x700
In that report the 0xffffffffc0660030 address corresponds to the former
function address of cxl_nvb_update_state() from a previous load of the
module, not the current address. Fix that by arranging for ->state_work
in the 'struct cxl_nvdimm_bridge' object to be reinitialized on cxl_pmem
module reload.
Details:
Recall that CXL subsystem wants to link a CXL memory expander device to
an NVDIMM sub-hierarchy when both a persistent memory range has been
registered by the CXL platform driver (cxl_acpi) *and* when that CXL
memory expander has published persistent memory capacity (Get Partition
Info). To this end the cxl_nvdimm_bridge driver arranges to rescan the
CXL bus when either of those conditions change. The helper
bus_rescan_devices() can not be called underneath the device_lock() for
any device on that bus, so the cxl_nvdimm_bridge driver uses a workqueue
for the rescan.
Typically a driver allocates driver data to hold a 'struct work_struct'
for a driven device, but for a workqueue that may run after ->remove()
returns, driver data will have been freed. The 'struct
cxl_nvdimm_bridge' object holds the state and work_struct directly.
Unfortunately it was only arranging for that infrastructure to be
initialized once per device creation rather than the necessary once per
workqueue (cxl_pmem_wq) creation.
Introduce is_cxl_nvdimm_bridge() and cxl_nvdimm_bridge_reset() in
support of invalidating stale references to a recently destroyed
cxl_pmem_wq.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 8fdcb1704f61 ("cxl/pmem: Add initial infrastructure for pmem support")
Reported-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/cxl/core/pmem.c | 8 +++++++-
drivers/cxl/cxl.h | 8 ++++++++
drivers/cxl/pmem.c | 29 +++++++++++++++++++++++++++--
3 files changed, 42 insertions(+), 3 deletions(-)
diff --git a/drivers/cxl/core/pmem.c b/drivers/cxl/core/pmem.c
index 76a4fa39834c..cc402cb7a905 100644
--- a/drivers/cxl/core/pmem.c
+++ b/drivers/cxl/core/pmem.c
@@ -51,10 +51,16 @@ struct cxl_nvdimm_bridge *to_cxl_nvdimm_bridge(struct device *dev)
}
EXPORT_SYMBOL_NS_GPL(to_cxl_nvdimm_bridge, CXL);
-__mock int match_nvdimm_bridge(struct device *dev, const void *data)
+bool is_cxl_nvdimm_bridge(struct device *dev)
{
return dev->type == &cxl_nvdimm_bridge_type;
}
+EXPORT_SYMBOL_NS_GPL(is_cxl_nvdimm_bridge, CXL);
+
+__mock int match_nvdimm_bridge(struct device *dev, const void *data)
+{
+ return is_cxl_nvdimm_bridge(dev);
+}
struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_nvdimm *cxl_nvd)
{
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 5e2e93451928..ca979ee11017 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -221,6 +221,13 @@ struct cxl_decoder {
};
+/**
+ * enum cxl_nvdimm_brige_state - state machine for managing bus rescans
+ * @CXL_NVB_NEW: Set at bridge create and after cxl_pmem_wq is destroyed
+ * @CXL_NVB_DEAD: Set at brige unregistration to preclude async probing
+ * @CXL_NVB_ONLINE: Target state after successful ->probe()
+ * @CXL_NVB_OFFLINE: Target state after ->remove() or failed ->probe()
+ */
enum cxl_nvdimm_brige_state {
CXL_NVB_NEW,
CXL_NVB_DEAD,
@@ -333,6 +340,7 @@ struct cxl_nvdimm_bridge *devm_cxl_add_nvdimm_bridge(struct device *host,
struct cxl_port *port);
struct cxl_nvdimm *to_cxl_nvdimm(struct device *dev);
bool is_cxl_nvdimm(struct device *dev);
+bool is_cxl_nvdimm_bridge(struct device *dev);
int devm_cxl_add_nvdimm(struct device *host, struct cxl_memdev *cxlmd);
struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_nvdimm *cxl_nvd);
diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
index 17e82ae90456..b65a272a2d6d 100644
--- a/drivers/cxl/pmem.c
+++ b/drivers/cxl/pmem.c
@@ -315,6 +315,31 @@ static struct cxl_driver cxl_nvdimm_bridge_driver = {
.id = CXL_DEVICE_NVDIMM_BRIDGE,
};
+/*
+ * Return all bridges to the CXL_NVB_NEW state to invalidate any
+ * ->state_work referring to the now destroyed cxl_pmem_wq.
+ */
+static int cxl_nvdimm_bridge_reset(struct device *dev, void *data)
+{
+ struct cxl_nvdimm_bridge *cxl_nvb;
+
+ if (!is_cxl_nvdimm_bridge(dev))
+ return 0;
+
+ cxl_nvb = to_cxl_nvdimm_bridge(dev);
+ device_lock(dev);
+ cxl_nvb->state = CXL_NVB_NEW;
+ device_unlock(dev);
+
+ return 0;
+}
+
+static void destroy_cxl_pmem_wq(void)
+{
+ destroy_workqueue(cxl_pmem_wq);
+ bus_for_each_dev(&cxl_bus_type, NULL, NULL, cxl_nvdimm_bridge_reset);
+}
+
static __init int cxl_pmem_init(void)
{
int rc;
@@ -340,7 +365,7 @@ static __init int cxl_pmem_init(void)
err_nvdimm:
cxl_driver_unregister(&cxl_nvdimm_bridge_driver);
err_bridge:
- destroy_workqueue(cxl_pmem_wq);
+ destroy_cxl_pmem_wq();
return rc;
}
@@ -348,7 +373,7 @@ static __exit void cxl_pmem_exit(void)
{
cxl_driver_unregister(&cxl_nvdimm_driver);
cxl_driver_unregister(&cxl_nvdimm_bridge_driver);
- destroy_workqueue(cxl_pmem_wq);
+ destroy_cxl_pmem_wq();
}
MODULE_LICENSE("GPL v2");
