@@ -194,6 +194,35 @@ static int acpi_processor_make_present(struct acpi_processor *pr)
return ret;
}
+static int acpi_processor_make_enabled(struct acpi_processor *pr)
+{
+ unsigned long long sta;
+ acpi_status status;
+ bool present, enabled;
+
+ if (!acpi_has_method(pr->handle, "_STA"))
+ return arch_register_cpu(pr->id);
+
+ status = acpi_evaluate_integer(pr->handle, "_STA", NULL, &sta);
+ if (ACPI_FAILURE(status))
+ return -ENODEV;
+
+ present = sta & ACPI_STA_DEVICE_PRESENT;
+ enabled = sta & ACPI_STA_DEVICE_ENABLED;
+
+ if (cpu_online(pr->id) && (!present || !enabled)) {
+ pr_err_once(FW_BUG "CPU %u is online, but described as not present or disabled!\n", pr->id);
+ add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
+ } else if (!present || !enabled) {
+ return -ENODEV;
+ }
+
+ if (get_cpu_device(pr->id))
+ return -EEXIST;
+
+ return arch_register_cpu(pr->id);
+}
+
static int acpi_processor_get_info(struct acpi_device *device)
{
union acpi_object object = { 0 };
@@ -271,7 +300,7 @@ static int acpi_processor_get_info(struct acpi_device *device)
}
if (!invalid_logical_cpuid(pr->id) && cpu_present(pr->id)) {
- int ret = arch_register_cpu(pr->id);
+ int ret = acpi_processor_make_enabled(pr);
if (ret)
return ret;
}
@@ -478,6 +507,9 @@ static void acpi_processor_post_eject(struct acpi_device *device)
acpi_processor_make_not_present(device);
return;
}
+
+ if (cpu_present(pr->id) && !(sta & ACPI_STA_DEVICE_ENABLED))
+ arch_unregister_cpu(pr->id);
}
#ifdef CONFIG_X86
acpi_processor_get_info() registers all present CPUs. Registering a CPU is what creates the sysfs entries and triggers the udev notifications. arm64 virtual machines that support 'virtual cpu hotplug' use the enabled bit to indicate whether the CPU can be brought online, as the existing ACPI tables require all hardware to be described and present. If firmware describes a CPU as present, but disabled, skip the registration. Such CPUs are present, but can't be brought online for whatever reason. (e.g. firmware/hypervisor policy). Once firmware sets the enabled bit, the CPU can be registered and brought online by user-space. Online CPUs, or CPUs that are missing an _STA method must always be registered. Signed-off-by: James Morse <james.morse@arm.com> --- drivers/acpi/acpi_processor.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-)