Hello James,
On 1/18/2017 7:50 AM, James Morse wrote:
Hi Tyler,
On 12/01/17 18:15, Tyler Baicar wrote:
ARM APEI extension proposal added SEA (Synchrounous External
Nit: Synchronous
I'll fix that :)
Abort) notification type for ARMv8.
Add a new GHES error source handling function for SEA. If an error
source's notification type is SEA, then this function can be registered
into the SEA exception handler. That way GHES will parse and report
SEA exceptions when they occur.
diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 2acbc60..87efe26 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -767,6 +772,62 @@ static struct notifier_block ghes_notifier_sci = {
.notifier_call = ghes_notify_sci,
};
+#ifdef CONFIG_HAVE_ACPI_APEI_SEA
+static LIST_HEAD(ghes_sea);
+
+static int ghes_notify_sea(struct notifier_block *this,
+ unsigned long event, void *data)
+{
+ struct ghes *ghes;
+ int ret = NOTIFY_DONE;
+
+ nmi_enter();
Can we move this into the arch code? Its because we got here from a
synchronous-exception that makes this nmi-like, I think it only makes sense for
it be called from under /arch/.
So move the nmi_enter/exit calls into do_sea of the previous patch? I
can do that in the next patchset.
Where did the rcu_read_lock() go? I can see its missing from ghes_notify_nmi()
too, but I don't know enough about RCU to know if that's safe!
The second paragraph in the comment above rcu_read_lock() describes it as
preventing call_rcu() during a read-side critical section that was running
concurrently. Doesn't this mean we can race with ghes_sea_remove() on another
CPU because we wait for the wrong grace period?
The same comment talks about how these read-side critical sections can nest, so
I think its quite safe to make these 'lock' calls here.
Sorry, I thought we wanted nmi_enter/exit instead of the
rcu_read_lock/unlock. I guess the rcu locks
will not cause the deadlock scenario you described in the previous
patchset if we have the
nmi_enter/exit wrapped around the rcu critical section.
+ list_for_each_entry_rcu(ghes, &ghes_sea, list) {
+ if (!ghes_proc(ghes))
+ ret = NOTIFY_OK;
+ }
+ nmi_exit();
+
+ return ret;
+}
+
+static struct notifier_block ghes_notifier_sea = {
+ .notifier_call = ghes_notify_sea,
+};
+
+static int ghes_sea_add(struct ghes *ghes)
+{
+ mutex_lock(&ghes_list_mutex);
+ if (list_empty(&ghes_sea))
+ register_sea_notifier(&ghes_notifier_sea);
+ list_add_rcu(&ghes->list, &ghes_sea);
+ mutex_unlock(&ghes_list_mutex);
+ return 0;
+}
+
+static void ghes_sea_remove(struct ghes *ghes)
+{
+ mutex_lock(&ghes_list_mutex);
+ list_del_rcu(&ghes->list);
+ if (list_empty(&ghes_sea))
+ unregister_sea_notifier(&ghes_notifier_sea);
+ mutex_unlock(&ghes_list_mutex);
ghes_nmi_remove() has:
/*
* To synchronize with NMI handler, ghes can only be
* freed after NMI handler finishes.
*/
synchronize_rcu()
This 'waits until a grace period has elapsed'. This is because ghes_remove()
goes and kfree()s the ghes object while another CPU may be holding that entry in
the list in ghes_notify_sea().
I will add synchronize_rcu() in the next patchset.
+}
+#else /* CONFIG_HAVE_ACPI_APEI_SEA */
+static inline int ghes_sea_add(struct ghes *ghes)
+{
+ pr_err(GHES_PFX "ID: %d, trying to add SEA notification which is not supported\n",
+ ghes->generic->header.source_id);
+ return -ENOTSUPP;
+}
+
+static inline void ghes_sea_remove(struct ghes *ghes)
+{
+ pr_err(GHES_PFX "ID: %d, trying to remove SEA notification which is not supported\n",
+ ghes->generic->header.source_id);
+}
+#endif /* CONFIG_HAVE_ACPI_APEI_SEA */
+
#ifdef CONFIG_HAVE_ACPI_APEI_NMI
/*
* printk is not safe in NMI context. So in NMI handler, we allocate
@@ -1011,6 +1072,14 @@ static int ghes_probe(struct platform_device *ghes_dev)
case ACPI_HEST_NOTIFY_EXTERNAL:
case ACPI_HEST_NOTIFY_SCI:
break;
+ case ACPI_HEST_NOTIFY_SEA:
+ if (!IS_ENABLED(CONFIG_HAVE_ACPI_APEI_SEA)) {
+ pr_warn(GHES_PFX "Generic hardware error source: %d notified via SEA is not supported\n",
+ generic->header.source_id);
+ rc = -ENOTSUPP;
+ goto err;
+ }
+ break;
case ACPI_HEST_NOTIFY_NMI:
if (!IS_ENABLED(CONFIG_HAVE_ACPI_APEI_NMI)) {
pr_warn(GHES_PFX "Generic hardware error source: %d notified via NMI interrupt is not supported!\n",
@@ -1022,6 +1091,13 @@ static int ghes_probe(struct platform_device *ghes_dev)
pr_warning(GHES_PFX "Generic hardware error source: %d notified via local interrupt is not supported!\n",
generic->header.source_id);
goto err;
+ case ACPI_HEST_NOTIFY_GPIO:
+ case ACPI_HEST_NOTIFY_SEI:
+ case ACPI_HEST_NOTIFY_GSIV:
These three weren't mentioned in the commit message. I guess they are drive-by
cleanup?
SEI and GSIV were also added in the ACPI 6.1 spec (18.3.2.9 Hardware
Error Notification) and GPIO was missing, so I added all three.
Thanks,
Tyler
+ pr_warn(GHES_PFX "Generic hardware error source: %d notified via notification type %u is not supported\n",
+ generic->header.source_id, generic->header.source_id);
+ rc = -ENOTSUPP;
+ goto err;
default:
pr_warning(FW_WARN GHES_PFX "Unknown notification type: %u for generic hardware error source: %d\n",
generic->notify.type, generic->header.source_id);
Thanks,
James
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