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SubjectRe: [PATCH V5 3/4] x86: Support Generic Initiator only proximity domains

* Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:

> Done in a somewhat different fashion to arm64.
> Here the infrastructure for memoryless domains was already
> in place. That infrastruture applies just as well to
> domains that also don't have a CPU, hence it works for
> Generic Initiator Domains.
>
> In common with memoryless domains we only register GI domains
> if the proximity node is not online. If a domain is already
> a memory containing domain, or a memoryless domain there is
> nothing to do just because it also contains a Generic Initiator.
>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
> arch/x86/include/asm/numa.h | 2 ++
> arch/x86/kernel/setup.c | 1 +
> arch/x86/mm/numa.c | 14 ++++++++++++++
> 3 files changed, 17 insertions(+)
>
> diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h
> index bbfde3d2662f..f631467272a3 100644
> --- a/arch/x86/include/asm/numa.h
> +++ b/arch/x86/include/asm/numa.h
> @@ -62,12 +62,14 @@ extern void numa_clear_node(int cpu);
> extern void __init init_cpu_to_node(void);
> extern void numa_add_cpu(int cpu);
> extern void numa_remove_cpu(int cpu);
> +extern void init_gi_nodes(void);
> #else /* CONFIG_NUMA */
> static inline void numa_set_node(int cpu, int node) { }
> static inline void numa_clear_node(int cpu) { }
> static inline void init_cpu_to_node(void) { }
> static inline void numa_add_cpu(int cpu) { }
> static inline void numa_remove_cpu(int cpu) { }
> +static inline void init_gi_nodes(void) { }
> #endif /* CONFIG_NUMA */
>
> #ifdef CONFIG_DEBUG_PER_CPU_MAPS
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index cfb533d42371..b6c977907ea5 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1264,6 +1264,7 @@ void __init setup_arch(char **cmdline_p)
> prefill_possible_map();
>
> init_cpu_to_node();
> + init_gi_nodes();
>
> io_apic_init_mappings();
>
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index 4123100e0eaf..50bf724a425e 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -733,6 +733,20 @@ static void __init init_memory_less_node(int nid)
> */
> }
>
> +/*
> + * Generic Initiator Nodes may have neither CPU nor Memory.
> + * At this stage if either of the others were present we would
> + * already be online.
> + */
> +void __init init_gi_nodes(void)
> +{
> + int nid;
> +
> + for_each_node_state(nid, N_GENERIC_INITIATOR)
> + if (!node_online(nid))
> + init_memory_less_node(nid);
> +}

Nit: missing curly braces.

How do these work in practice, will a system that only had nodes 0-1
today grow a third node '2' that won't have any CPUs on memory on them?

Thanks,

Ingo

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