[PATCH 1/4] ACPI: APEI: GHES: Use spin_lock_irqsave() for CXL CPER work locks

[Dave Jiang <dave.jiang@intel.com>]

cxl_cper_post_event() and cxl_cper_post_prot_err() acquire
cxl_cper_work_lock and cxl_cper_prot_err_work_lock with
spin_lock_irqsave(). These producers run from ghes_do_proc() in hard IRQ
context (the GHES IRQ handler) and, for SEA/NMI notifications, from NMI
context.

The register/unregister helpers take the same two locks with a plain
spin_lock() from process context (cxl_ras_init()/cxl_ras_exit() at module
load and unload). If a GHES error interrupt is delivered to a CPU that is
holding one of these locks via the plain spin_lock(), the interrupt
handler's spin_lock_irqsave() on the same lock spins forever against a
lock the interrupted thread can no longer release.

Take these locks with spin_lock_irqsave() on the register/unregister
paths as well.

Link: https://sashiko.dev/#/patchset/20260617-topics-ahmtib01-ras_ffh_arm_internal_review-v6-0-91f725174aa0@arm.com?part=6
Fixes: 5e4a264bf8b5 ("acpi/ghes: Process CXL Component Events")
Fixes: 36f257e3b0ba ("acpi/ghes, cxl/pci: Process CXL CPER Protocol Errors")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/acpi/apei/ghes.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 3236a3ce79d6..9b6917698ed2 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -783,7 +783,7 @@ int cxl_cper_register_prot_err_work(struct work_struct *work)
 	if (cxl_cper_prot_err_work)
 		return -EINVAL;
 
-	guard(spinlock)(&cxl_cper_prot_err_work_lock);
+	guard(spinlock_irqsave)(&cxl_cper_prot_err_work_lock);
 	cxl_cper_prot_err_work = work;
 	return 0;
 }
@@ -794,7 +794,7 @@ int cxl_cper_unregister_prot_err_work(struct work_struct *work)
 	if (cxl_cper_prot_err_work != work)
 		return -EINVAL;
 
-	guard(spinlock)(&cxl_cper_prot_err_work_lock);
+	guard(spinlock_irqsave)(&cxl_cper_prot_err_work_lock);
 	cxl_cper_prot_err_work = NULL;
 	return 0;
 }
@@ -852,7 +852,7 @@ int cxl_cper_register_work(struct work_struct *work)
 	if (cxl_cper_work)
 		return -EINVAL;
 
-	guard(spinlock)(&cxl_cper_work_lock);
+	guard(spinlock_irqsave)(&cxl_cper_work_lock);
 	cxl_cper_work = work;
 	return 0;
 }
@@ -863,7 +863,7 @@ int cxl_cper_unregister_work(struct work_struct *work)
 	if (cxl_cper_work != work)
 		return -EINVAL;
 
-	guard(spinlock)(&cxl_cper_work_lock);
+	guard(spinlock_irqsave)(&cxl_cper_work_lock);
 	cxl_cper_work = NULL;
 	return 0;
 }
-- 
2.54.0