On Thu, Sep 24, 2020 at 04:50:54PM -0300, Daniel Henrique Barboza wrote: > The pSeries machine does not support asymmetrical NUMA > configurations. This doesn't make much of a different > since we're not using user input for pSeries NUMA setup, > but this will change in the next patches. > > To avoid breaking existing setups, gate this change by > checking for legacy NUMA support. > > Reviewed-by: Greg Kurz <gr...@kaod.org> > Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com>
Having read the rest of the series, I realized there's another type of
configuration that PAPR can't represent, so possibly we should add
logic to catch that as well. That's what I'm going to call
"non-transitive" configurations, e.g.
Node 0 1 2
0 10 20 40
1 20 10 20
2 40 20 10
Basically the closeness of 0 to 1 and 1 to 2 forces them all to be in
the same domain at every PAPR level, even though 0-2 is supposed to be
more expensive.
> ---
> hw/ppc/spapr_numa.c | 34 ++++++++++++++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
>
> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
> index 64fe567f5d..fe395e80a3 100644
> --- a/hw/ppc/spapr_numa.c
> +++ b/hw/ppc/spapr_numa.c
> @@ -19,6 +19,24 @@
> /* Moved from hw/ppc/spapr_pci_nvlink2.c */
> #define SPAPR_GPU_NUMA_ID (cpu_to_be32(1))
>
> +static bool spapr_numa_is_symmetrical(MachineState *ms)
> +{
> + int src, dst;
> + int nb_numa_nodes = ms->numa_state->num_nodes;
> + NodeInfo *numa_info = ms->numa_state->nodes;
> +
> + for (src = 0; src < nb_numa_nodes; src++) {
> + for (dst = src; dst < nb_numa_nodes; dst++) {
> + if (numa_info[src].distance[dst] !=
> + numa_info[dst].distance[src]) {
> + return false;
> + }
> + }
> + }
> +
> + return true;
> +}
> +
> void spapr_numa_associativity_init(SpaprMachineState *spapr,
> MachineState *machine)
> {
> @@ -61,6 +79,22 @@ void spapr_numa_associativity_init(SpaprMachineState
> *spapr,
>
> spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i);
> }
> +
> + /*
> + * Legacy NUMA guests (pseries-5.1 and older, or guests with only
> + * 1 NUMA node) will not benefit from anything we're going to do
> + * after this point.
> + */
> + if (spapr_machine_using_legacy_numa(spapr)) {
> + return;
> + }
> +
> + if (!spapr_numa_is_symmetrical(machine)) {
> + error_report("Asymmetrical NUMA topologies aren't supported "
> + "in the pSeries machine");
> + exit(EXIT_FAILURE);
> + }
> +
> }
>
> void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt,
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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