On Wed, 13 Sep 2023 16:38:10 +0000
James Morse <james.morse@xxxxxxx> wrote:
> 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.
Will be fun to see how many such buggy firmwares are out there.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
Comment inline but not directly related to this patch so with or
without that change
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> ---
> drivers/acpi/acpi_processor.c | 31 +++++++++++++++++++++++++------
> include/linux/cpu.h | 1 +
> 2 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index 00dcc23d49a8..2cafea1edc24 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))
Would it be possible to do all the ifdef to IS_ENABLED changes in a separate
patch? I haven't figure out if any of them have dependencies on the other
changes, but they do create a bunch of noise I'd rather not see in the more
complex corners of this.
> 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,
> },
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index a71691d7c2ca..e117c06e0c6b 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -81,6 +81,7 @@ struct device *cpu_device_create(struct device *parent, void *drvdata,
> const struct attribute_group **groups,
> const char *fmt, ...);
> extern int arch_register_cpu(int cpu);
> +extern void arch_unregister_cpu(int cpu);
> #ifdef CONFIG_HOTPLUG_CPU
> extern void unregister_cpu(struct cpu *cpu);
> extern ssize_t arch_cpu_probe(const char *, size_t);
