Re: [PATCH v9 01/19] ACPI: processor: Simplify initial onlining to use same path for cold and hotplug

[Miguel Luis <miguel.luis@oracle.com>]

> On 30 Apr 2024, at 14:24, Jonathan Cameron <jonathan.cameron@huawei.com> wrote:
> 
> Separate code paths, combined with a flag set in acpi_processor.c to
> indicate a struct acpi_processor was for a hotplugged CPU ensured that
> per CPU data was only set up the first time that a CPU was initialized.
> This appears to be unnecessary as the paths can be combined by letting
> the online logic also handle any CPUs online at the time of driver load.
> 
> Motivation for this change, beyond simplification, is that ARM64
> virtual CPU HP uses the same code paths for hotplug and cold path in
> acpi_processor.c so had no easy way to set the flag for hotplug only.
> Removing this necessity will enable ARM64 vCPU HP to reuse the existing
> code paths.
> 
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
> Tested-by: Miguel Luis <miguel.luis@oracle.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> ---
> v9: Drop overly noisy pr_info() print and tidy up a stale comment about
>    the flag that no longer exists. Leave in place the note about delayed
>    init.
> ---
> drivers/acpi/acpi_processor.c   |  7 +++---
> drivers/acpi/processor_driver.c | 43 +++++++++------------------------
> include/acpi/processor.h        |  2 +-
> 3 files changed, 16 insertions(+), 36 deletions(-)
> 

Looks good to me.

Reviewed-by: Miguel Luis <miguel.luis@oracle.com>

Thank you,
Miguel

> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index 7a0dd35d62c9..b2f0b6c19482 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -211,12 +211,11 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
> }
> 
> /*
> - * CPU got hot-added, but cpu_data is not initialized yet.  Set a flag
> - * to delay cpu_idle/throttling initialization and do it when the CPU
> - * gets online for the first time.
> + * CPU got hot-added, but cpu_data is not initialized yet. Do
> + * cpu_idle/throttling initialization when the CPU gets online for
> + * the first time.
> */
> pr_info("CPU%d has been hot-added\n", pr->id);
> - pr->flags.need_hotplug_init = 1;
> 
> out:
> cpus_write_unlock();
> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index 67db60eda370..cb52dd000b95 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -33,7 +33,6 @@ MODULE_AUTHOR("Paul Diefenbaugh");
> MODULE_DESCRIPTION("ACPI Processor Driver");
> MODULE_LICENSE("GPL");
> 
> -static int acpi_processor_start(struct device *dev);
> static int acpi_processor_stop(struct device *dev);
> 
> static const struct acpi_device_id processor_device_ids[] = {
> @@ -47,7 +46,6 @@ static struct device_driver acpi_processor_driver = {
> .name = "processor",
> .bus = &cpu_subsys,
> .acpi_match_table = processor_device_ids,
> - .probe = acpi_processor_start,
> .remove = acpi_processor_stop,
> };
> 
> @@ -115,12 +113,9 @@ static int acpi_soft_cpu_online(unsigned int cpu)
> * CPU got physically hotplugged and onlined for the first time:
> * Initialize missing things.
> */
> - if (pr->flags.need_hotplug_init) {
> + if (!pr->flags.previously_online) {
> int ret;
> 
> - pr_info("Will online and init hotplugged CPU: %d\n",
> - pr->id);
> - pr->flags.need_hotplug_init = 0;
> ret = __acpi_processor_start(device);
> WARN(ret, "Failed to start CPU: %d\n", pr->id);
> } else {
> @@ -167,9 +162,6 @@ static int __acpi_processor_start(struct acpi_device *device)
> if (!pr)
> return -ENODEV;
> 
> - if (pr->flags.need_hotplug_init)
> - return 0;
> -
> result = acpi_cppc_processor_probe(pr);
> if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
> dev_dbg(&device->dev, "CPPC data invalid or not present\n");
> @@ -185,32 +177,21 @@ static int __acpi_processor_start(struct acpi_device *device)
> 
> status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
>     acpi_processor_notify, device);
> - if (ACPI_SUCCESS(status))
> - return 0;
> + if (!ACPI_SUCCESS(status)) {
> + result = -ENODEV;
> + goto err_thermal_exit;
> + }
> + pr->flags.previously_online = 1;
> 
> - result = -ENODEV;
> - acpi_processor_thermal_exit(pr, device);
> + return 0;
> 
> +err_thermal_exit:
> + acpi_processor_thermal_exit(pr, device);
> err_power_exit:
> acpi_processor_power_exit(pr);
> return result;
> }
> 
> -static int acpi_processor_start(struct device *dev)
> -{
> - struct acpi_device *device = ACPI_COMPANION(dev);
> - int ret;
> -
> - if (!device)
> - return -ENODEV;
> -
> - /* Protect against concurrent CPU hotplug operations */
> - cpu_hotplug_disable();
> - ret = __acpi_processor_start(device);
> - cpu_hotplug_enable();
> - return ret;
> -}
> -
> static int acpi_processor_stop(struct device *dev)
> {
> struct acpi_device *device = ACPI_COMPANION(dev);
> @@ -279,9 +260,9 @@ static int __init acpi_processor_driver_init(void)
> if (result < 0)
> return result;
> 
> - result = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
> -   "acpi/cpu-drv:online",
> -   acpi_soft_cpu_online, NULL);
> + result = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
> +   "acpi/cpu-drv:online",
> +   acpi_soft_cpu_online, NULL);
> if (result < 0)
> goto err;
> hp_online = result;
> diff --git a/include/acpi/processor.h b/include/acpi/processor.h
> index 3f34ebb27525..e6f6074eadbf 100644
> --- a/include/acpi/processor.h
> +++ b/include/acpi/processor.h
> @@ -217,7 +217,7 @@ struct acpi_processor_flags {
> u8 has_lpi:1;
> u8 power_setup_done:1;
> u8 bm_rld_set:1;
> - u8 need_hotplug_init:1;
> + u8 previously_online:1;
> };
> 
> struct acpi_processor {
> -- 
> 2.39.2
>