Re: [Qemu-arm] [PATCH v4 7/7] numa: cpu: calculate/set default node-ids after all -numa CLI options are parsed

[Eduardo Habkost]

On Thu, Jun 01, 2017 at 12:53:28PM +0200, Igor Mammedov wrote:
> Calculating default node-ids for CPUs in possible_cpu_arch_ids()
> is rather fragile since defaults calculation uses nb_numa_nodes but
> callback might be potentially called early before all -numa CLI
> options are parsed, which would lead to cpus assigned only upto
> nb_numa_nodes at the time possible_cpu_arch_ids() is called.
> 
> Issue was introduced by
> (7c88e65 numa: mirror cpu to node mapping in MachineState::possible_cpus)
> and for example CLI:
>   -smp 4 -numa node,cpus=0 -numa node
> would set props.node-id in possible_cpus array for every non
> explicitly mapped CPU to the first node.
> 
> Issue is not visible to guest nor to mgmt interface due to
>   1) implictly mapped cpus are forced to the first node in
>      case of partial mapping
>   2) in case of default mapping possible_cpu_arch_ids() is
>      called after all -numa options are parsed (resulting
>      in correct mapping).
> 
> However it's fragile to rely on late execution of
> possible_cpu_arch_ids(), therefore add machine specific
> callback that returns node-id for CPU and use it to calculate/
> set defaults at machine_numa_finish_init() time when all -numa
> options are parsed.
> 
> Reported-by: Eduardo Habkost <address@hidden>
> Signed-off-by: Igor Mammedov <address@hidden>

Reviewed-by: Eduardo Habkost <address@hidden>

Queued on numa-next.  Thanks!

-- 
Eduardo