Re: [PATCH v5 2/4] hw/arm/virt: Consider SMP configuration in CPU topology

["Daniel P. Berrangé" <berrange@redhat.com>]

On Sun, Apr 03, 2022 at 10:59:51PM +0800, Gavin Shan wrote:
> Currently, the SMP configuration isn't considered when the CPU
> topology is populated. In this case, it's impossible to provide
> the default CPU-to-NUMA mapping or association based on the socket
> ID of the given CPU.
> 
> This takes account of SMP configuration when the CPU topology
> is populated. The die ID for the given CPU isn't assigned since
> it's not supported on arm/virt machine yet.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  hw/arm/virt.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index d2e5ecd234..3174526730 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2505,6 +2505,7 @@ static const CPUArchIdList *virt_possible_cpu_arch_ids(MachineState *ms)
>      int n;
>      unsigned int max_cpus = ms->smp.max_cpus;
>      VirtMachineState *vms = VIRT_MACHINE(ms);
> +    MachineClass *mc = MACHINE_GET_CLASS(vms);
>  
>      if (ms->possible_cpus) {
>          assert(ms->possible_cpus->len == max_cpus);
> @@ -2518,8 +2519,21 @@ static const CPUArchIdList *virt_possible_cpu_arch_ids(MachineState *ms)
>          ms->possible_cpus->cpus[n].type = ms->cpu_type;
>          ms->possible_cpus->cpus[n].arch_id =
>              virt_cpu_mp_affinity(vms, n);
> +
> +        assert(!mc->smp_props.dies_supported);
> +        ms->possible_cpus->cpus[n].props.has_socket_id = true;
> +        ms->possible_cpus->cpus[n].props.socket_id =
> +            (n / (ms->smp.clusters * ms->smp.cores * ms->smp.threads)) %
> +            ms->smp.sockets;
> +        ms->possible_cpus->cpus[n].props.has_cluster_id = true;
> +        ms->possible_cpus->cpus[n].props.cluster_id =
> +            (n / (ms->smp.cores * ms->smp.threads)) % ms->smp.clusters;
> +        ms->possible_cpus->cpus[n].props.has_core_id = true;
> +        ms->possible_cpus->cpus[n].props.core_id =
> +            (n / ms->smp.threads) % ms->smp.cores;
>          ms->possible_cpus->cpus[n].props.has_thread_id = true;
> -        ms->possible_cpus->cpus[n].props.thread_id = n;
> +        ms->possible_cpus->cpus[n].props.thread_id =
> +            n % ms->smp.threads;

Does this need to be conditionalized d behind a machine property, so that
we don't change behaviour of existing machine type versions ?

With regards,
Daniel
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