[PATCH 27/39] ACPI: Check _STA present bit before making CPUs not present

Russell King
2023-10-24T15:22:12Z

When called acpi_processor_post_eject() unconditionally make a CPU
not-present and unregisters it.

To add support for AML events where the CPU has become disabled, but
remains present, the _STA method should be checked before calling
acpi_processor_remove().

Rename acpi_processor_post_eject() acpi_processor_remove_possible(), and
check the _STA before calling.

Adding the function prototype for arch_unregister_cpu() allows the
preprocessor guards to be removed.

After this change CPUs will remain registered and visible to
user-space as offline if buggy firmware triggers an eject-request,
but doesn't clear the corresponding _STA bits after _EJ0 has been
called.

Signed-off-by: James Morse <james.morse@arm.com>
---
drivers/acpi/acpi_processor.c | 31 +++++++++++++++++++++++++------
1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index b6f5005985c3..19fceb3ec4e2 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -457,13 +457,12 @@ static int acpi_processor_add(struct acpi_device *device,
return result;
}

-#ifdef CONFIG_ACPI_HOTPLUG_PRESENT_CPU
/* Removal */
-static void acpi_processor_post_eject(struct acpi_device *device)
+static void acpi_processor_make_not_present(struct acpi_device *device)
{
struct acpi_processor *pr;

- if (!device || !acpi_driver_data(device))
+ if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_PRESENT_CPU))
return;

pr = acpi_driver_data(device);
@@ -501,7 +500,29 @@ static void acpi_processor_post_eject(struct acpi_device *device)
free_cpumask_var(pr->throttling.shared_cpu_map);
kfree(pr);
}
-#endif /* CONFIG_ACPI_HOTPLUG_PRESENT_CPU */
+
+static void acpi_processor_post_eject(struct acpi_device *device)
+{
+ struct acpi_processor *pr;
+ unsigned long long sta;
+ acpi_status status;
+
+ if (!device)
+ return;
+
+ pr = acpi_driver_data(device);
+ if (!pr || pr->id >= nr_cpu_ids || invalid_phys_cpuid(pr->phys_id))
+ return;
+
+ status = acpi_evaluate_integer(pr->handle, "_STA", NULL, &sta);
+ if (ACPI_FAILURE(status))
+ return;
+
+ if (cpu_present(pr->id) && !(sta & ACPI_STA_DEVICE_PRESENT)) {
+ acpi_processor_make_not_present(device);
+ return;
+ }
+}

#ifdef CONFIG_ARCH_MIGHT_HAVE_ACPI_PDC
bool __init processor_physically_present(acpi_handle handle)
@@ -626,9 +647,7 @@ static const struct acpi_device_id processor_device_ids[] = {
static struct acpi_scan_handler processor_handler = {
.ids = processor_device_ids,
.attach = acpi_processor_add,
-#ifdef CONFIG_ACPI_HOTPLUG_PRESENT_CPU
.post_eject = acpi_processor_post_eject,
-#endif
.hotplug = {
.enabled = true,
},
--
2.30.2