linux-kernel - Re: [PATCH 1/3] acpi/processor: fix evaluating

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Date:   Fri, 3 Feb 2023 08:05:04 +0100
From:   Jan Beulich <jbeulich@...e.com>
To:     Josef Johansson <josef@...rland.se>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-acpi@...r.kernel.org, Roger Pau Monne <roger.pau@...rix.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] acpi/processor: fix evaluating _PDC method when
 running as Xen dom0

On 30.01.2023 10:21, Josef Johansson wrote:
> On 11/21/22 11:21, Roger Pau Monne wrote:
>> --- a/arch/x86/xen/enlighten.c
>> +++ b/arch/x86/xen/enlighten.c
>> @@ -346,3 +346,30 @@ void xen_arch_unregister_cpu(int num)
>>   }
>>   EXPORT_SYMBOL(xen_arch_unregister_cpu);
>>   #endif
>> +
>> +#ifdef CONFIG_XEN_DOM0
>> +bool __init xen_processor_present(uint32_t acpi_id)
>> +{
>> +	unsigned int i, maxid;
>> +	struct xen_platform_op op = {
>> +		.cmd = XENPF_get_cpuinfo,
>> +		.interface_version = XENPF_INTERFACE_VERSION,
>> +	};
>> +	int ret = HYPERVISOR_platform_op(&op);
>> +
>> +	if (ret)
>> +		return false;
>> +
>> +	maxid = op.u.pcpu_info.max_present;
>> +	for (i = 0; i <= maxid; i++) {
>> +		op.u.pcpu_info.xen_cpuid = i;
>> +		ret = HYPERVISOR_platform_op(&op);
>> +		if (ret)
>> +			continue;
>> +		if (op.u.pcpu_info.acpi_id == acpi_id)
>> +			return op.u.pcpu_info.flags & XEN_PCPU_FLAGS_ONLINE;
>> +	}
>> +
>> +	return false;
>> +}
> My compiler (Default GCC on Fedora 32, compiling for Qubes) complain 
> loudly that the below was missing.
> 
> +}
> +EXPORT_SYMBOL(xen_processor_present);
> 
> `ERROR: MODPOST xen_processor_present 
> [drivers/xen/xen-acpi-processor.ko] undefined!`
> 
> Same thing with xen_sanitize_pdc in the next patch.
> 
> +}
> +EXPORT_SYMBOL(xen_sanitize_pdc);
> 
> Everything compiled fine after those changes.

Except that you may not export __init symbols. The section mismatch checker
should actually complain about that.

Jan