linux-kernel - Re: [RFC PATCH v2 23/35] ACPI: Warn when the present bit changes but the feature is not enabled

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Message-ID: <54c91de8-f0d2-787f-5710-2da1dfc80937@redhat.com>
Date:   Tue, 19 Sep 2023 10:49:32 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     James Morse <james.morse@....com>, linux-pm@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-acpi@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev
Cc:     x86@...nel.org, Salil Mehta <salil.mehta@...wei.com>,
        Russell King <linux@...linux.org.uk>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        jianyong.wu@....com, justin.he@....com
Subject: Re: [RFC PATCH v2 23/35] ACPI: Warn when the present bit changes but
 the feature is not enabled



On 9/14/23 02:38, James Morse wrote:
> ACPI firmware can trigger the events to add and remove CPUs, but the
> OS may not support this.
> 
> Print a warning when this happens.
           ^^^^^^^
           error message
> 
> This gives early warning on arm64 systems that don't support
> CONFIG_ACPI_HOTPLUG_PRESENT_CPU, as making CPUs not present has
> side effects for other parts of the system.
> 
> Signed-off-by: James Morse <james.morse@....com>
> ---
>   drivers/acpi/acpi_processor.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 

Maybe a warning message is enough, but a error message
is also fine, I think.

Reviewed-by: Gavin Shan <gshan@...hat.com>

> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index 2cafea1edc24..b67616079751 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -188,8 +188,10 @@ static int acpi_processor_make_present(struct acpi_processor *pr)
>   	acpi_status status;
>   	int ret;
>   
> -	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_PRESENT_CPU))
> +	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_PRESENT_CPU)) {
> +		pr_err_once("Changing CPU present bit is not supported\n");
>   		return -ENODEV;
> +	}
>   
>   	if (invalid_phys_cpuid(pr->phys_id))
>   		return -ENODEV;
> @@ -462,8 +464,10 @@ static void acpi_processor_make_not_present(struct acpi_device *device)
>   {
>   	struct acpi_processor *pr;
>   
> -	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_PRESENT_CPU))
> +	if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_PRESENT_CPU)) {
> +		pr_err_once("Changing CPU present bit is not supported");
>   		return;
> +	}
>   
>   	pr = acpi_driver_data(device);
>   	if (pr->id >= nr_cpu_ids)

Thanks,
Gavin