Re: [Qemu-devel] [PATCH for 2.13 v2 1/2] spapr: Add ibm, max-associativity-domains property

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Apr 10, 2018 at 02:12:25PM -0400, Serhii Popovych wrote:
> Now recent kernels (i.e. since linux-stable commit a346137e9142
> ("powerpc/numa: Use ibm,max-associativity-domains to discover possible nodes")
> support this property to mark initially memory-less NUMA nodes as "possible"
> to allow further memory hot-add to them.
> 
> Advertise this property for pSeries machines to let guest kernels detect
> maximum supported node configuration and benefit from kernel side change
> when hot-add memory to specific, possibly empty before, NUMA node.
> 
> Signed-off-by: Serhii Popovych <spopovyc@redhat.com>
> ---
>  hw/ppc/spapr.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 2c0be8c..3f61785 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -909,6 +909,14 @@ static void spapr_dt_rtas(sPAPRMachineState *spapr, void *fdt)
>          0, cpu_to_be32(SPAPR_MEMORY_BLOCK_SIZE),
>          cpu_to_be32(max_cpus / smp_threads),
>      };
> +    uint32_t maxdomains[] = {
> +        cpu_to_be32(5),
> +        cpu_to_be32(0),
> +        cpu_to_be32(0),
> +        cpu_to_be32(0),
> +        cpu_to_be32(nb_numa_nodes - 1),
> +        cpu_to_be32(0),
> +    };

Ah.. close, but not quite right.  This is saying that there's exactly
one node at the bottom (cpu) level, which isn't what we want.  Instead
of setting it to 0, we want to completely drop that layer, keeping it
unspecified.

To do that you need to change the first cell from 5 to 4 (since only 4
levels will be listed) and drop the last cell entirely.

>      _FDT(rtas = fdt_add_subnode(fdt, 0, "rtas"));
>  
> @@ -945,6 +953,9 @@ static void spapr_dt_rtas(sPAPRMachineState *spapr, void *fdt)
>      _FDT(fdt_setprop(fdt, rtas, "ibm,associativity-reference-points",
>                       refpoints, sizeof(refpoints)));
>  
> +    _FDT(fdt_setprop(fdt, rtas, "ibm,max-associativity-domains",
> +                     maxdomains, sizeof(maxdomains)));
> +
>      _FDT(fdt_setprop_cell(fdt, rtas, "rtas-error-log-max",
>                            RTAS_ERROR_LOG_MAX));
>      _FDT(fdt_setprop_cell(fdt, rtas, "rtas-event-scan-rate",

-- 
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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