ACPI / APEI: Generalise the estatus queue's notify code

Refactor the estatus queue's pool notification routine from
NOTIFY_NMI's handlers. This will allow another notification
method to use the estatus queue without duplicating this code.

Add rcu_read_lock()/rcu_read_unlock() around the list
list_for_each_entry_rcu() walker. These aren't strictly necessary as
the whole nmi_enter/nmi_exit() window is a spooky RCU read-side
critical section.

in_nmi_queue_one_entry() is separate from the rcu-list walker for a
later caller that doesn't need to walk a list.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Punit Agrawal <punit.agrawal@arm.com>
Tested-by: Tyler Baicar <tbaicar@codeaurora.org>
[ rjw: Drop unnecessary err variable in two places ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index af3c10f47f20c49f9d169a9003cff59574228648..babd2d53f319a3453d3646799c892daf52dbf2ca 100644 (file)
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -912,37 +912,56 @@ static void __process_error(struct ghes *ghes)
 #endif
 }
 
-static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
+static int ghes_in_nmi_queue_one_entry(struct ghes *ghes)
 {
        u64 buf_paddr;
-       struct ghes *ghes;
-       int sev, ret = NMI_DONE;
+       int sev;
 
-       if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
-               return ret;
+       if (ghes_read_estatus(ghes, &buf_paddr)) {
+               ghes_clear_estatus(ghes, buf_paddr);
+               return -ENOENT;
+       }
 
-       list_for_each_entry_rcu(ghes, &ghes_nmi, list) {
-               if (ghes_read_estatus(ghes, &buf_paddr)) {
-                       ghes_clear_estatus(ghes, buf_paddr);
-                       continue;
-               } else {
-                       ret = NMI_HANDLED;
-               }
+       sev = ghes_severity(ghes->estatus->error_severity);
+       if (sev >= GHES_SEV_PANIC) {
+               ghes_print_queued_estatus();
+               __ghes_panic(ghes, buf_paddr);
+       }
 
-               sev = ghes_severity(ghes->estatus->error_severity);
-               if (sev >= GHES_SEV_PANIC) {
-                       ghes_print_queued_estatus();
-                       __ghes_panic(ghes, buf_paddr);
-               }
+       __process_error(ghes);
+       ghes_clear_estatus(ghes, buf_paddr);
 
-               __process_error(ghes);
-               ghes_clear_estatus(ghes, buf_paddr);
+       return 0;
+}
+
+static int ghes_in_nmi_spool_from_list(struct list_head *rcu_list)
+{
+       int ret = -ENOENT;
+       struct ghes *ghes;
+
+       rcu_read_lock();
+       list_for_each_entry_rcu(ghes, rcu_list, list) {
+               if (!ghes_in_nmi_queue_one_entry(ghes))
+                       ret = 0;
        }
+       rcu_read_unlock();
 
-#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
-       if (ret == NMI_HANDLED)
+       if (IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && !ret)
                irq_work_queue(&ghes_proc_irq_work);
-#endif
+
+       return ret;
+}
+
+static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
+{
+       int ret = NMI_DONE;
+
+       if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
+               return ret;
+
+       if (!ghes_in_nmi_spool_from_list(&ghes_nmi))
+               ret = NMI_HANDLED;
+
        atomic_dec(&ghes_in_nmi);
        return ret;
 }