[PATCH v6 02/18] ACPI / APEI: Generalise the estatus queue's add/remove and notify code

James Morse
2018-09-21T22:17:53Z

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

This patch adds 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.

The existing ghes_estatus_pool_shrink() is folded into the new
ghes_estatus_queue_shrink_pool() as only the queue uses it.

_in_nmi_notify_one() 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>

---
Changes since v3:
* Removed dupicate or redundant paragraphs in commit message.
* Fixed the style of a zero check
Changes since v1:
* Tidied up _in_nmi_notify_one().
---
drivers/acpi/apei/ghes.c | 100 +++++++++++++++++++++++++--------------
1 file changed, 65 insertions(+), 35 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index f5732e6b5be8..29d863ff2f87 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -747,6 +747,51 @@ static void __process_error(struct ghes *ghes)
#endif
}

+static int _in_nmi_notify_one(struct ghes *ghes)
+{
+ int sev;
+
+ if (ghes_read_estatus(ghes, 1)) {
+ ghes_clear_estatus(ghes);
+ return -ENOENT;
+ }
+
+ sev = ghes_severity(ghes->estatus->error_severity);
+ if (sev >= GHES_SEV_PANIC) {
+#ifdef CONFIG_X86
+ oops_begin();
+#endif
+ ghes_print_queued_estatus();
+ __ghes_panic(ghes);
+ }
+
+ if (!(ghes->flags & GHES_TO_CLEAR))
+ return 0;
+
+ __process_error(ghes);
+ ghes_clear_estatus(ghes);
+
+ return 0;
+}
+
+static int ghes_estatus_queue_notified(struct list_head *rcu_list)
+{
+ int ret = -ENOENT;
+ struct ghes *ghes;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(ghes, rcu_list, list) {
+ if (!_in_nmi_notify_one(ghes))
+ ret = 0;
+ }
+ rcu_read_unlock();
+
+ if (IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && !ret)
+ irq_work_queue(&ghes_proc_irq_work);
+
+ return ret;
+}
+
static unsigned long ghes_esource_prealloc_size(
const struct acpi_hest_generic *generic)
{
@@ -762,11 +807,24 @@ static unsigned long ghes_esource_prealloc_size(
return prealloc_size;
}

-static void ghes_estatus_pool_shrink(unsigned long len)
+/* After removing a queue user, we can shrink the pool */
+static void ghes_estatus_queue_shrink_pool(struct ghes *ghes)
{
+ unsigned long len;
+
+ len = ghes_esource_prealloc_size(ghes->generic);
ghes_estatus_pool_size_request -= PAGE_ALIGN(len);
}

+/* Before adding a queue user, grow the pool */
+static void ghes_estatus_queue_grow_pool(struct ghes *ghes)
+{
+ unsigned long len;
+
+ len = ghes_esource_prealloc_size(ghes->generic);
+ ghes_estatus_pool_expand(len);
+}
+
static void ghes_proc_in_irq(struct irq_work *irq_work)
{
struct llist_node *llnode, *next;
@@ -965,48 +1023,22 @@ static LIST_HEAD(ghes_nmi);

static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
{
- struct ghes *ghes;
- int sev, ret = NMI_DONE;
+ int ret = NMI_DONE;

if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
return ret;

- list_for_each_entry_rcu(ghes, &ghes_nmi, list) {
- if (ghes_read_estatus(ghes, 1)) {
- ghes_clear_estatus(ghes);
- continue;
- } else {
- ret = NMI_HANDLED;
- }
-
- sev = ghes_severity(ghes->estatus->error_severity);
- if (sev >= GHES_SEV_PANIC) {
- oops_begin();
- ghes_print_queued_estatus();
- __ghes_panic(ghes);
- }
+ if (!ghes_estatus_queue_notified(&ghes_nmi))
+ ret = NMI_HANDLED;

- if (!(ghes->flags & GHES_TO_CLEAR))
- continue;
-
- __process_error(ghes);
- ghes_clear_estatus(ghes);
- }
-
-#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
- if (ret == NMI_HANDLED)
- irq_work_queue(&ghes_proc_irq_work);
-#endif
atomic_dec(&ghes_in_nmi);
return ret;
}

static void ghes_nmi_add(struct ghes *ghes)
{
- unsigned long len;
+ ghes_estatus_queue_grow_pool(ghes);

- len = ghes_esource_prealloc_size(ghes->generic);
- ghes_estatus_pool_expand(len);
mutex_lock(&ghes_list_mutex);
if (list_empty(&ghes_nmi))
register_nmi_handler(NMI_LOCAL, ghes_notify_nmi, 0, "ghes");
@@ -1016,8 +1048,6 @@ static void ghes_nmi_add(struct ghes *ghes)

static void ghes_nmi_remove(struct ghes *ghes)
{
- unsigned long len;
-
mutex_lock(&ghes_list_mutex);
list_del_rcu(&ghes->list);
if (list_empty(&ghes_nmi))
@@ -1028,8 +1058,8 @@ static void ghes_nmi_remove(struct ghes *ghes)
* freed after NMI handler finishes.
*/
synchronize_rcu();
- len = ghes_esource_prealloc_size(ghes->generic);
- ghes_estatus_pool_shrink(len);
+
+ ghes_estatus_queue_shrink_pool(ghes);
}

#else /* CONFIG_HAVE_ACPI_APEI_NMI */
--
2.19.0