linux-kernel - Re: [PATCH v6 04/16] ACPI: processor: Move checks and availability of acpi

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Message-ID: <20240417174707.00002e86@huawei.com>
Date: Thu, 18 Apr 2024 09:16:27 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra
	<peterz@...radead.org>, <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>, <kvmarm@...ts.linux.dev>,
	<x86@...nel.org>, Russell King <linux@...linux.org.uk>, "Rafael J . Wysocki"
	<rafael@...nel.org>, Miguel Luis <miguel.luis@...cle.com>, "James Morse"
	<james.morse@....com>, Salil Mehta <salil.mehta@...wei.com>, Jean-Philippe
 Brucker <jean-philippe@...aro.org>, Catalin Marinas
	<catalin.marinas@....com>, Will Deacon <will@...nel.org>,
	<linuxarm@...wei.com>
CC: Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "Dave
 Hansen" <dave.hansen@...ux.intel.com>, <justin.he@....com>,
	<jianyong.wu@....com>
Subject: Re: [PATCH v6 04/16] ACPI: processor: Move checks and availability
 of acpi_processor earlier

On Wed, 17 Apr 2024 14:18:57 +0100
Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:

> Make the per_cpu(processors, cpu) entries available earlier so that
> they are available in arch_register_cpu() as ARM64 will need access
> to the acpi_handle to distinguish between acpi_processor_add()
> and earlier registration attempts (which will fail as _STA cannot
> be checked).
> 
> Reorder the remove flow to clear this per_cpu() after
> arch_unregister_cpu() has completed, allowing it to be used in
> there as well.
> 
> Note that on x86 for the CPU hotplug case, the pr->id prior to
> acpi_map_cpu() may be invalid. Thus the per_cpu() structures
> must be initialized after that call or after checking the ID
> is valid (not hotplug path).
> 
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
> v6: As per discussion in v5 thread, don't use the cpu->dev and
>     make this data available earlier by moving the assignment checks
>     int acpi_processor_get_info().
> ---
>  drivers/acpi/acpi_processor.c | 79 +++++++++++++++++++++--------------
>  1 file changed, 47 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index ba0a6f0ac841..2c164451ab53 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -184,7 +184,35 @@ static void __init acpi_pcc_cpufreq_init(void) {}
>  
>  /* Initialization */
>  #ifdef CONFIG_ACPI_HOTPLUG_CPU
Note I messed up a rebase here.  This ifdef should come after the new function
(see later)

Will fix for v7.
> -static int acpi_processor_hotadd_init(struct acpi_processor *pr)
> +static DEFINE_PER_CPU(void *, processor_device_array);
> +
> +static void acpi_processor_set_per_cpu(struct acpi_processor *pr,
> +				       struct acpi_device *device)
> +{
> +	BUG_ON(pr->id >= nr_cpu_ids);
> +	/*
> +	 * Buggy BIOS check.
> +	 * ACPI id of processors can be reported wrongly by the BIOS.
> +	 * Don't trust it blindly
> +	 */
> +	if (per_cpu(processor_device_array, pr->id) != NULL &&
> +	    per_cpu(processor_device_array, pr->id) != device) {
> +		dev_warn(&device->dev,
> +			 "BIOS reported wrong ACPI id %d for the processor\n",
> +			 pr->id);
> +		/* Give up, but do not abort the namespace scan. */
> +		return;
> +	}
> +	/*
> +	 * processor_device_array is not cleared on errors to allow buggy BIOS
> +	 * checks.
> +	 */
> +	per_cpu(processor_device_array, pr->id) = device;
> +	per_cpu(processors, pr->id) = pr;
> +}
> +

The ifdef should be here as...

> +static int acpi_processor_hotadd_init(struct acpi_processor *pr,
> +				      struct acpi_device *device)
>  {
>  	int ret;
>  
> @@ -198,6 +226,8 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
>  	if (ret)
>  		goto out;
>  
> +	acpi_processor_set_per_cpu(pr, device);
> +
>  	ret = arch_register_cpu(pr->id);
>  	if (ret) {
>  		acpi_unmap_cpu(pr->id);
> @@ -217,7 +247,8 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
>  	return ret;
>  }
>  #else
> -static inline int acpi_processor_hotadd_init(struct acpi_processor *pr)
> +static inline int acpi_processor_hotadd_init(struct acpi_processor *pr,
> +					     struct acpi_device *device)
>  {
>  	return -ENODEV;
>  }
> @@ -232,6 +263,7 @@ static int acpi_processor_get_info(struct acpi_device *device)
>  	acpi_status status = AE_OK;
>  	static int cpu0_initialized;
>  	unsigned long long value;
> +	int ret;
>  
>  	acpi_processor_errata();
>  
> @@ -316,10 +348,12 @@ static int acpi_processor_get_info(struct acpi_device *device)
>  	 *  because cpuid <-> apicid mapping is persistent now.
>  	 */
>  	if (invalid_logical_cpuid(pr->id) || !cpu_present(pr->id)) {
> -		int ret = acpi_processor_hotadd_init(pr);
> +		ret = acpi_processor_hotadd_init(pr, device);
>  
>  		if (ret)
> -			return ret;
> +			goto err;
> +	} else {
> +		acpi_processor_set_per_cpu(pr, device);

This is not covered by CONFIG_ACPI_HOTPLUG_CPU

>  	}