[PATCH v19 04/14] cxl: Tighten CPER kfifo registration API and symbol visibility

[Terry Bowman <terry.bowman@amd.com>]

From: Dan Williams <djbw@kernel.org>

Tighten the CPER protocol error kfifo registration API and symbol
visibility.

Use EXPORT_SYMBOL_FOR_MODULES() instead of EXPORT_SYMBOL_NS_GPL() for
the CPER kfifo registration symbols. This names the consuming module
explicitly and gives compile-time enforcement.

Drop the work_struct argument from the unregister path. Change the
WARN_ONCE condition to a NULL check since there is no caller pointer
to compare against anymore.

Return void from the registration helpers whose result callers ignore.
cxl_cper_register_work() keeps its int return as the only one consumed by
a caller. Flag double registration with WARN_ONCE() inside the lock
instead of returning an error.

Change cxl_ras_init() to void because there is one consumer and one
producer so the error return was unnecessary. Remove the now-dead error
check in cxl_core_init().

Co-developed-by: Terry Bowman <terry.bowman@amd.com>
Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Signed-off-by: Dan Williams <djbw@kernel.org>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>

---

Changes in v18 -> v19:
- Tidied up definition line-wrapping in event.h
- Refined commit message reason for converting reg/dreg function
return values to NULL.
- Add review-by for DaveJ

Changes in v17 -> v18:
- New patch.
---
 drivers/acpi/apei/ghes.c | 32 +++++++++++++++-----------------
 drivers/cxl/core/core.h  |  7 ++-----
 drivers/cxl/core/port.c  |  6 +-----
 drivers/cxl/core/ras.c   |  6 +++---
 include/cxl/event.h      | 21 ++++++---------------
 5 files changed, 27 insertions(+), 45 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index ca7a138c1ff2e..187f54e31c33e 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -778,41 +778,41 @@ static void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,
 #endif
 }
 
-int cxl_cper_register_prot_err_work(struct work_struct *work)
+void cxl_cper_register_prot_err_work(struct work_struct *work)
 {
 	guard(raw_spinlock_irqsave)(&cxl_cper_prot_err_work_lock);
 
 	if (WARN_ONCE(cxl_cper_prot_err_work,
 		      "CPER-CXL kfifo consumer already registered\n"))
-		return -EINVAL;
+		return;
 	cxl_cper_prot_err_work = work;
-	return 0;
 }
-EXPORT_SYMBOL_NS_GPL(cxl_cper_register_prot_err_work, "CXL");
+EXPORT_SYMBOL_FOR_MODULES(cxl_cper_register_prot_err_work, "cxl_core");
 
-int cxl_cper_unregister_prot_err_work(struct work_struct *work)
+void cxl_cper_unregister_prot_err_work(void)
 {
+	struct work_struct *old;
+
 	scoped_guard(raw_spinlock_irqsave, &cxl_cper_prot_err_work_lock) {
-		if (WARN_ONCE(cxl_cper_prot_err_work != work,
-			      "CPER-CXL kfifo consumer mismatch on unregister\n"))
-			return -EINVAL;
+		WARN_ONCE(!cxl_cper_prot_err_work,
+			  "CPER-CXL kfifo consumer not registered on unregister\n");
+		old = cxl_cper_prot_err_work;
 		cxl_cper_prot_err_work = NULL;
 	}
 
-	cancel_work_sync(work);
+	if (old)
+		cancel_work_sync(old);
 
 	/* Discard stale entries so they are not replayed on next module load */
 	kfifo_reset(&cxl_cper_prot_err_fifo);
-
-	return 0;
 }
-EXPORT_SYMBOL_NS_GPL(cxl_cper_unregister_prot_err_work, "CXL");
+EXPORT_SYMBOL_FOR_MODULES(cxl_cper_unregister_prot_err_work, "cxl_core");
 
 int cxl_cper_prot_err_kfifo_get(struct cxl_cper_prot_err_work_data *wd)
 {
 	return kfifo_get(&cxl_cper_prot_err_fifo, wd);
 }
-EXPORT_SYMBOL_NS_GPL(cxl_cper_prot_err_kfifo_get, "CXL");
+EXPORT_SYMBOL_FOR_MODULES(cxl_cper_prot_err_kfifo_get, "cxl_core");
 
 /* Room for 8 entries for each of the 4 event log queues */
 #define CXL_CPER_FIFO_DEPTH 32
@@ -867,12 +867,12 @@ int cxl_cper_register_work(struct work_struct *work)
 }
 EXPORT_SYMBOL_NS_GPL(cxl_cper_register_work, "CXL");
 
-int cxl_cper_unregister_work(struct work_struct *work)
+void cxl_cper_unregister_work(struct work_struct *work)
 {
 	scoped_guard(raw_spinlock_irqsave, &cxl_cper_work_lock) {
 		if (WARN_ONCE(cxl_cper_work != work,
 			      "CXL CPER kfifo consumer mismatch on unregister\n"))
-			return -EINVAL;
+			return;
 		cxl_cper_work = NULL;
 	}
 
@@ -880,8 +880,6 @@ int cxl_cper_unregister_work(struct work_struct *work)
 
 	/* Discard stale entries so they are not replayed on next module load */
 	kfifo_reset(&cxl_cper_fifo);
-
-	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_cper_unregister_work, "CXL");
 
diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 07555ae638594..23fe40ddf4c6b 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -183,7 +183,7 @@ static inline struct device *dport_to_host(struct cxl_dport *dport)
 	return &port->dev;
 }
 #ifdef CONFIG_CXL_RAS
-int cxl_ras_init(void);
+void cxl_ras_init(void);
 void cxl_ras_exit(void);
 bool cxl_handle_ras(struct device *dev, void __iomem *ras_base);
 void cxl_handle_cor_ras(struct device *dev, void __iomem *ras_base);
@@ -192,10 +192,7 @@ void cxl_disable_rch_root_ints(struct cxl_dport *dport);
 void cxl_handle_rdport_errors(struct cxl_dev_state *cxlds);
 void devm_cxl_dport_ras_setup(struct cxl_dport *dport);
 #else
-static inline int cxl_ras_init(void)
-{
-	return 0;
-}
+static inline void cxl_ras_init(void) { }
 static inline void cxl_ras_exit(void) { }
 static inline bool cxl_handle_ras(struct device *dev, void __iomem *ras_base)
 {
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 1215ee4f40351..f90f899c31d07 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -2531,14 +2531,10 @@ static __init int cxl_core_init(void)
 	if (rc)
 		goto err_region;
 
-	rc = cxl_ras_init();
-	if (rc)
-		goto err_ras;
+	cxl_ras_init();
 
 	return 0;
 
-err_ras:
-	cxl_region_exit();
 err_region:
 	bus_unregister(&cxl_bus_type);
 err_bus:
diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
index bc74d4848132e..e307361bb39e4 100644
--- a/drivers/cxl/core/ras.c
+++ b/drivers/cxl/core/ras.c
@@ -129,14 +129,14 @@ static void cxl_cper_prot_err_work_fn(struct work_struct *work)
 }
 static DECLARE_WORK(cxl_cper_prot_err_work, cxl_cper_prot_err_work_fn);
 
-int cxl_ras_init(void)
+void cxl_ras_init(void)
 {
-	return cxl_cper_register_prot_err_work(&cxl_cper_prot_err_work);
+	cxl_cper_register_prot_err_work(&cxl_cper_prot_err_work);
 }
 
 void cxl_ras_exit(void)
 {
-	cxl_cper_unregister_prot_err_work(&cxl_cper_prot_err_work);
+	cxl_cper_unregister_prot_err_work();
 }
 
 static void cxl_dport_map_ras(struct cxl_dport *dport)
diff --git a/include/cxl/event.h b/include/cxl/event.h
index ff97fea718d2c..b5673384d9306 100644
--- a/include/cxl/event.h
+++ b/include/cxl/event.h
@@ -287,10 +287,10 @@ struct cxl_cper_prot_err_work_data {
 
 #ifdef CONFIG_ACPI_APEI_GHES
 int cxl_cper_register_work(struct work_struct *work);
-int cxl_cper_unregister_work(struct work_struct *work);
+void cxl_cper_unregister_work(struct work_struct *work);
 int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd);
-int cxl_cper_register_prot_err_work(struct work_struct *work);
-int cxl_cper_unregister_prot_err_work(struct work_struct *work);
+void cxl_cper_register_prot_err_work(struct work_struct *work);
+void cxl_cper_unregister_prot_err_work(void);
 int cxl_cper_prot_err_kfifo_get(struct cxl_cper_prot_err_work_data *wd);
 #else
 static inline int cxl_cper_register_work(struct work_struct *work)
@@ -298,22 +298,13 @@ static inline int cxl_cper_register_work(struct work_struct *work)
 	return 0;
 }
 
-static inline int cxl_cper_unregister_work(struct work_struct *work)
-{
-	return 0;
-}
+static inline void cxl_cper_unregister_work(struct work_struct *work) { }
 static inline int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd)
 {
 	return 0;
 }
-static inline int cxl_cper_register_prot_err_work(struct work_struct *work)
-{
-	return 0;
-}
-static inline int cxl_cper_unregister_prot_err_work(struct work_struct *work)
-{
-	return 0;
-}
+static inline void cxl_cper_register_prot_err_work(struct work_struct *work) { }
+static inline void cxl_cper_unregister_prot_err_work(void) { }
 static inline int cxl_cper_prot_err_kfifo_get(struct cxl_cper_prot_err_work_data *wd)
 {
 	return 0;
-- 
2.34.1