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SubjectRe: [RFC PATCH] x86/acpi: Ignore invalid x2APIC entries
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On Fri, Jul 28 2023 at 14:51, Thomas Gleixner wrote:
> On Mon, Jul 03 2023 at 00:28, Zhang Rui wrote:
>>
>> +static bool has_lapic_cpus;
>
> Yet another random flag. Sigh.
>
> I really hate this. Why not doing the obvious?
>
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -2452,6 +2452,9 @@ int generic_processor_info(int apicid, i
> bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
> phys_cpu_present_map);
>
> + if (physid_isset(apicid, phys_cpu_present_map))
> + return -EBUSY;
> +
> /*
> * boot_cpu_physical_apicid is designed to have the apicid
> * returned by read_apic_id(), i.e, the apicid of the
>
> As the call sites during MADT parsing ignore the return value anyway,
> there is no harm and this is a proper defense against broken tables
> which enumerate an APIC twice.

In fact that function should not have a return value at all, but because
it's not clearly separated between boot time and physical hotplug, it
has to have one ...

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