On Thu, 2021-11-11 at 10:19 -0800, Dan Williams wrote:
A test of the form:
while true; do modprobe -r cxl_pmem; modprobe cxl_pmem; doneMay 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/0x700In 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@vger.kernel.org Fixes: 8fdcb1704f61 ("cxl/pmem: Add initial infrastructure for pmem support") Reported-by: Vishal Verma vishal.l.verma@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com
Tried this out and works fine now, thanks for the quick fix!
Tested-by: Vishal Verma vishal.l.verma@intel.com
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");