[PATCH v4 04/13] ACPI: extlog: Defer CXL protocol error handling to avoid lock inversion

extlog_print() calls cxl_cper_handle_prot_err() synchronously while the
MCE notifier chain rwsem is held, and that path takes the PCI device_lock
via guard(device)(). The probe path takes the two in the opposite order,
holding device_lock while mce_register_decode_chain() takes the rwsem, so
they can deadlock AB-BA.

ghes.c already avoids this by posting protocol errors to a kfifo and
handling them from a workqueue via cxl_cper_post_prot_err(). Export that
function and call it instead.

Declare it with the other CONFIG_ACPI_APEI_GHES exports rather than at the
end of the header. No #else stub: ACPI_EXTLOG selects ACPI_APEI_GHES, so
the only caller cannot exist without it.

Reported-by: [email protected]
Closes: https://lore.kernel.org/linux-cxl/[email protected]/
Reviewed-by: Alison Schofield <[email protected]>
Reviewed-by: Shuai Xue <[email protected]>
Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Dave Jiang <[email protected]>
---
v4:
- Moved the cxl_cper_post_prot_err() declaration inside the
  CONFIG_ACPI_APEI_GHES block (Shuai Xue).
---
 drivers/acpi/acpi_extlog.c | 21 ++-------------------
 drivers/acpi/apei/ghes.c   |  5 +++--
 include/acpi/ghes.h        |  4 ++++
 3 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
index 9ad0052aa20c..f6e3da4e13e7 100644
--- a/drivers/acpi/acpi_extlog.c
+++ b/drivers/acpi/acpi_extlog.c
@@ -163,23 +163,6 @@ static void extlog_print_pcie(struct cper_sec_pcie *pcie_err,
 #endif
 }
 
-static void
-extlog_cxl_cper_handle_prot_err(struct cxl_cper_sec_prot_err *prot_err,
-				int severity)
-{
-#ifdef ACPI_APEI_PCIEAER
-	struct cxl_cper_prot_err_work_data wd;
-
-	if (cxl_cper_sec_prot_err_valid(prot_err))
-		return;
-
-	if (cxl_cper_setup_prot_err_work_data(&wd, prot_err, severity))
-		return;
-
-	cxl_cper_handle_prot_err(&wd);
-#endif
-}
-
 static int extlog_print(struct notifier_block *nb, unsigned long val,
 			void *data)
 {
@@ -239,8 +222,8 @@ static int extlog_print(struct notifier_block *nb, unsigned long val,
 			struct cxl_cper_sec_prot_err *prot_err =
 				acpi_hest_get_payload(gdata);
 
-			extlog_cxl_cper_handle_prot_err(prot_err,
-							gdata->error_severity);
+			cxl_cper_post_prot_err(prot_err,
+					       gdata->error_severity);
 		} else if (guid_equal(sec_type, &CPER_SEC_PCIE)) {
 			struct cper_sec_pcie *pcie_err = acpi_hest_get_payload(gdata);
 
diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 3236a3ce79d6..a382aabf9835 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -752,8 +752,8 @@ static DEFINE_KFIFO(cxl_cper_prot_err_fifo, struct cxl_cper_prot_err_work_data,
 static DEFINE_SPINLOCK(cxl_cper_prot_err_work_lock);
 struct work_struct *cxl_cper_prot_err_work;
 
-static void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,
-				   int severity)
+void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,
+			    int severity)
 {
 #ifdef CONFIG_ACPI_APEI_PCIEAER
 	struct cxl_cper_prot_err_work_data wd;
@@ -777,6 +777,7 @@ static void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,
 	schedule_work(cxl_cper_prot_err_work);
 #endif
 }
+EXPORT_SYMBOL_FOR_MODULES(cxl_cper_post_prot_err, "acpi_extlog");
 
 int cxl_cper_register_prot_err_work(struct work_struct *work)
 {
diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h
index 8d7e5caef3f1..be496bc0386f 100644
--- a/include/acpi/ghes.h
+++ b/include/acpi/ghes.h
@@ -85,6 +85,10 @@ int devm_ghes_register_vendor_record_notifier(struct device *dev,
 struct list_head *ghes_get_devices(void);
 
 void ghes_estatus_pool_region_free(unsigned long addr, u32 size);
+
+struct cxl_cper_sec_prot_err;
+void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,
+			    int severity);
 #else
 static inline struct list_head *ghes_get_devices(void) { return NULL; }
 
-- 
2.54.0