From 9e8407aeddf2960ddca6c28d886fa740071eef88 Mon Sep 17 00:00:00 2001 From: James Morse Date: Fri, 2 Jul 2021 17:11:07 +0100 Subject: ACPI: add support to register CPUs based on the _STA enabled bit 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 Signed-off-by: Russell King (Oracle) --- drivers/acpi/acpi_processor.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c index 60d5fdb24128..eb5faa74b138 100644 --- a/drivers/acpi/acpi_processor.c +++ b/drivers/acpi/acpi_processor.c @@ -235,6 +235,35 @@ out: 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 }; @@ -320,7 +349,7 @@ 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; } @@ -527,6 +556,9 @@ 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 -- cgit