Re: [Qemu-devel] [PATCH v3 2/8] cpu: introduce possible-cpus interface

[Eduardo Habkost]

On Tue, Feb 23, 2016 at 05:05:54PM +0100, Igor Mammedov wrote:
> on x86 currently range 0..max_cpus is used to generate
> architecture-dependent CPU ID (APIC Id) for each present
> and possible CPUs. However architecture-dependent CPU IDs
> list could be sparse and code that needs to enumerate
> all IDs (ACPI) ended up doing guess work enumerating all
> possible and impossible IDs up to
>   apic_id_limit = x86_cpu_apic_id_from_index(max_cpus).
> 
> That leads to creation of MADT/SRAT entries and Processor
> objects in ACPI tables for not possible CPUs.
> Fix it by allowing board specify a concrete list of
> CPU IDs accourding its own rules (which for x86 depends
> on topology). So that code that needs this list could
> request it from board instead of trying to figure out
> what IDs are correct on its own.
> 
> This interface will also allow to help making AML
> part of CPU hotplug target independent so it could
> be reused for ARM target.

Do you expect any non-TYPE_MACHINE class to implement this
interface? If not, why not just make it a simple MachineClass
field? Machines that don't implement the get_possible_cpus_list()
method would just have it set to NULL.

-- 
Eduardo