Re: [PATCH v12 4/5] arm64, numa: Add NUMA support for arm64 platforms.

[David Daney <ddaney@caviumnetworks.com>]

+ Bjorn Helgaas

Bjorn,

I Inadvertently omitted you from the list of recipients.  There is an 
arm64 PCI bit in here that may be of interest...

On 02/22/2016 05:58 PM, David Daney wrote:
> From: Ganapatrao Kulkarni <gkulkarni@caviumnetworks.com>
>
> Attempt to get the memory and CPU NUMA node via of_numa.  If that
> fails, default the dummy NUMA node and map all memory and CPUs to node
> 0.
>
> Tested-by: Shannon Zhao <shannon.zhao@linaro.org>
> Reviewed-by: Robert Richter <rrichter@cavium.com>
> Signed-off-by: Ganapatrao Kulkarni <gkulkarni@caviumnetworks.com>
> Signed-off-by: David Daney <david.daney@cavium.com>
> ---
>   arch/arm64/Kconfig                |  26 +++
>   arch/arm64/include/asm/mmzone.h   |  12 ++
>   arch/arm64/include/asm/numa.h     |  45 +++++
>   arch/arm64/include/asm/topology.h |  10 +
>   arch/arm64/kernel/pci.c           |  10 +
>   arch/arm64/kernel/setup.c         |   4 +
>   arch/arm64/kernel/smp.c           |   4 +
>   arch/arm64/mm/Makefile            |   1 +
>   arch/arm64/mm/init.c              |  34 +++-
>   arch/arm64/mm/mmu.c               |   1 +
>   arch/arm64/mm/numa.c              | 403 ++++++++++++++++++++++++++++++++++++++
>   11 files changed, 545 insertions(+), 5 deletions(-)
>   create mode 100644 arch/arm64/include/asm/mmzone.h
>   create mode 100644 arch/arm64/include/asm/numa.h
>   create mode 100644 arch/arm64/mm/numa.c
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index a969970..9f0972a 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -74,6 +74,7 @@ config ARM64
>   	select HAVE_HW_BREAKPOINT if PERF_EVENTS
>   	select HAVE_IRQ_TIME_ACCOUNTING
>   	select HAVE_MEMBLOCK
> +	select HAVE_MEMBLOCK_NODE_MAP if NUMA
>   	select HAVE_PATA_PLATFORM
>   	select HAVE_PERF_EVENTS
>   	select HAVE_PERF_REGS
> @@ -96,6 +97,7 @@ config ARM64
>   	select SYSCTL_EXCEPTION_TRACE
>   	select HAVE_CONTEXT_TRACKING
>   	select HAVE_ARM_SMCCC
> +	select OF_NUMA if NUMA && OF
>   	help
>   	  ARM 64-bit (AArch64) Linux support.
>
> @@ -545,6 +547,30 @@ config HOTPLUG_CPU
>   	  Say Y here to experiment with turning CPUs off and on.  CPUs
>   	  can be controlled through /sys/devices/system/cpu.
>
> +# Common NUMA Features
> +config NUMA
> +	bool "Numa Memory Allocation and Scheduler Support"
> +	depends on SMP
> +	help
> +	  Enable NUMA (Non Uniform Memory Access) support.
> +
> +	  The kernel will try to allocate memory used by a CPU on the
> +	  local memory of the CPU and add some more
> +	  NUMA awareness to the kernel.
> +
> +config NODES_SHIFT
> +	int "Maximum NUMA Nodes (as a power of 2)"
> +	range 1 10
> +	default "2"
> +	depends on NEED_MULTIPLE_NODES
> +	help
> +	  Specify the maximum number of NUMA Nodes available on the target
> +	  system.  Increases memory reserved to accommodate various tables.
> +
> +config USE_PERCPU_NUMA_NODE_ID
> +	def_bool y
> +	depends on NUMA
> +
>   source kernel/Kconfig.preempt
>   source kernel/Kconfig.hz
>
> diff --git a/arch/arm64/include/asm/mmzone.h b/arch/arm64/include/asm/mmzone.h
> new file mode 100644
> index 0000000..a0de9e6
> --- /dev/null
> +++ b/arch/arm64/include/asm/mmzone.h
> @@ -0,0 +1,12 @@
> +#ifndef __ASM_MMZONE_H
> +#define __ASM_MMZONE_H
> +
> +#ifdef CONFIG_NUMA
> +
> +#include <asm/numa.h>
> +
> +extern struct pglist_data *node_data[];
> +#define NODE_DATA(nid)		(node_data[(nid)])
> +
> +#endif /* CONFIG_NUMA */
> +#endif /* __ASM_MMZONE_H */
> diff --git a/arch/arm64/include/asm/numa.h b/arch/arm64/include/asm/numa.h
> new file mode 100644
> index 0000000..e9b4f29
> --- /dev/null
> +++ b/arch/arm64/include/asm/numa.h
> @@ -0,0 +1,45 @@
> +#ifndef __ASM_NUMA_H
> +#define __ASM_NUMA_H
> +
> +#include <asm/topology.h>
> +
> +#ifdef CONFIG_NUMA
> +
> +/* currently, arm64 implements flat NUMA topology */
> +#define parent_node(node)	(node)
> +
> +int __node_distance(int from, int to);
> +#define node_distance(a, b) __node_distance(a, b)
> +
> +extern nodemask_t numa_nodes_parsed __initdata;
> +
> +/* Mappings between node number and cpus on that node. */
> +extern cpumask_var_t node_to_cpumask_map[MAX_NUMNODES];
> +void numa_clear_node(unsigned int cpu);
> +
> +#ifdef CONFIG_DEBUG_PER_CPU_MAPS
> +const struct cpumask *cpumask_of_node(int node);
> +#else
> +/* Returns a pointer to the cpumask of CPUs on Node 'node'. */
> +static inline const struct cpumask *cpumask_of_node(int node)
> +{
> +	return node_to_cpumask_map[node];
> +}
> +#endif
> +
> +void __init arm64_numa_init(void);
> +int __init numa_add_memblk(int nodeid, u64 start, u64 end);
> +void __init numa_set_distance(int from, int to, int distance);
> +void __init numa_free_distance(void);
> +void __init early_map_cpu_to_node(unsigned int cpu, int nid);
> +void numa_store_cpu_info(unsigned int cpu);
> +
> +#else	/* CONFIG_NUMA */
> +
> +static inline void numa_store_cpu_info(unsigned int cpu) { }
> +static inline void arm64_numa_init(void) { }
> +static inline void early_map_cpu_to_node(unsigned int cpu, int nid) { }
> +
> +#endif	/* CONFIG_NUMA */
> +
> +#endif	/* __ASM_NUMA_H */
> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> index a3e9d6f..8b57339 100644
> --- a/arch/arm64/include/asm/topology.h
> +++ b/arch/arm64/include/asm/topology.h
> @@ -22,6 +22,16 @@ void init_cpu_topology(void);
>   void store_cpu_topology(unsigned int cpuid);
>   const struct cpumask *cpu_coregroup_mask(int cpu);
>
> +#ifdef CONFIG_NUMA
> +
> +struct pci_bus;
> +int pcibus_to_node(struct pci_bus *bus);
> +#define cpumask_of_pcibus(bus)	(pcibus_to_node(bus) == -1 ?		\
> +				 cpu_all_mask :				\
> +				 cpumask_of_node(pcibus_to_node(bus)))
> +
> +#endif /* CONFIG_NUMA */
> +
>   #include <asm-generic/topology.h>
>
>   #endif /* _ASM_ARM_TOPOLOGY_H */
> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> index b3d098b..65e6b7d 100644
> --- a/arch/arm64/kernel/pci.c
> +++ b/arch/arm64/kernel/pci.c
> @@ -76,6 +76,16 @@ int raw_pci_write(unsigned int domain, unsigned int bus,
>   	return -ENXIO;
>   }
>
> +#ifdef CONFIG_NUMA
> +
> +int pcibus_to_node(struct pci_bus *bus)
> +{
> +	return dev_to_node(&bus->dev);
> +}
> +EXPORT_SYMBOL(pcibus_to_node);
> +
> +#endif
> +
>   #ifdef CONFIG_ACPI
>   /* Root bridge scanning */
>   struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 8119479..d9b9761 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -53,6 +53,7 @@
>   #include <asm/cpufeature.h>
>   #include <asm/cpu_ops.h>
>   #include <asm/kasan.h>
> +#include <asm/numa.h>
>   #include <asm/sections.h>
>   #include <asm/setup.h>
>   #include <asm/smp_plat.h>
> @@ -372,6 +373,9 @@ static int __init topology_init(void)
>   {
>   	int i;
>
> +	for_each_online_node(i)
> +		register_one_node(i);
> +
>   	for_each_possible_cpu(i) {
>   		struct cpu *cpu = &per_cpu(cpu_data.cpu, i);
>   		cpu->hotpluggable = 1;
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index b1adc51..46c45c8 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -45,6 +45,7 @@
>   #include <asm/cputype.h>
>   #include <asm/cpu_ops.h>
>   #include <asm/mmu_context.h>
> +#include <asm/numa.h>
>   #include <asm/pgtable.h>
>   #include <asm/pgalloc.h>
>   #include <asm/processor.h>
> @@ -125,6 +126,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
>   static void smp_store_cpu_info(unsigned int cpuid)
>   {
>   	store_cpu_topology(cpuid);
> +	numa_store_cpu_info(cpuid);
>   }
>
>   /*
> @@ -518,6 +520,8 @@ static void __init of_parse_and_init_cpus(void)
>
>   		pr_debug("cpu logical map 0x%llx\n", hwid);
>   		cpu_logical_map(cpu_count) = hwid;
> +
> +		early_map_cpu_to_node(cpu_count, of_node_to_nid(dn));
>   next:
>   		cpu_count++;
>   	}
> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
> index 57f57fd..54bb209 100644
> --- a/arch/arm64/mm/Makefile
> +++ b/arch/arm64/mm/Makefile
> @@ -4,6 +4,7 @@ obj-y				:= dma-mapping.o extable.o fault.o init.o \
>   				   context.o proc.o pageattr.o
>   obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
>   obj-$(CONFIG_ARM64_PTDUMP)	+= dump.o
> +obj-$(CONFIG_NUMA)		+= numa.o
>
>   obj-$(CONFIG_KASAN)		+= kasan_init.o
>   KASAN_SANITIZE_kasan_init.o	:= n
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index f3b061e..c39c670 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -37,6 +37,7 @@
>
>   #include <asm/fixmap.h>
>   #include <asm/memory.h>
> +#include <asm/numa.h>
>   #include <asm/sections.h>
>   #include <asm/setup.h>
>   #include <asm/sizes.h>
> @@ -77,6 +78,21 @@ static phys_addr_t __init max_zone_dma_phys(void)
>   	return min(offset + (1ULL << 32), memblock_end_of_DRAM());
>   }
>
> +#ifdef CONFIG_NUMA
> +
> +static void __init zone_sizes_init(unsigned long min, unsigned long max)
> +{
> +	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
> +
> +	if (IS_ENABLED(CONFIG_ZONE_DMA))
> +		max_zone_pfns[ZONE_DMA] = PFN_DOWN(max_zone_dma_phys());
> +	max_zone_pfns[ZONE_NORMAL] = max;
> +
> +	free_area_init_nodes(max_zone_pfns);
> +}
> +
> +#else
> +
>   static void __init zone_sizes_init(unsigned long min, unsigned long max)
>   {
>   	struct memblock_region *reg;
> @@ -117,6 +133,8 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>   	free_area_init_node(0, zone_size, min, zhole_size);
>   }
>
> +#endif /* CONFIG_NUMA */
> +
>   #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>   int pfn_valid(unsigned long pfn)
>   {
> @@ -133,10 +151,15 @@ static void __init arm64_memory_present(void)
>   static void __init arm64_memory_present(void)
>   {
>   	struct memblock_region *reg;
> +	int nid = 0;
>
> -	for_each_memblock(memory, reg)
> -		memory_present(0, memblock_region_memory_base_pfn(reg),
> -			       memblock_region_memory_end_pfn(reg));
> +	for_each_memblock(memory, reg) {
> +#ifdef CONFIG_NUMA
> +		nid = reg->nid;
> +#endif
> +		memory_present(nid, memblock_region_memory_base_pfn(reg),
> +				memblock_region_memory_end_pfn(reg));
> +	}
>   }
>   #endif
>
> @@ -181,7 +204,6 @@ void __init arm64_memblock_init(void)
>   	dma_contiguous_reserve(arm64_dma_phys_limit);
>
>   	memblock_allow_resize();
> -	memblock_dump_all();
>   }
>
>   void __init bootmem_init(void)
> @@ -193,6 +215,9 @@ void __init bootmem_init(void)
>
>   	early_memtest(min << PAGE_SHIFT, max << PAGE_SHIFT);
>
> +	max_pfn = max_low_pfn = max;
> +
> +	arm64_numa_init();
>   	/*
>   	 * Sparsemem tries to allocate bootmem in memory_present(), so must be
>   	 * done after the fixed reservations.
> @@ -203,7 +228,6 @@ void __init bootmem_init(void)
>   	zone_sizes_init(min, max);
>
>   	high_memory = __va((max << PAGE_SHIFT) - 1) + 1;
> -	max_pfn = max_low_pfn = max;
>   }
>
>   #ifndef CONFIG_SPARSEMEM_VMEMMAP
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 58faeaa..44e3854 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -463,6 +463,7 @@ void __init paging_init(void)
>   	zero_page = early_alloc(PAGE_SIZE);
>
>   	bootmem_init();
> +	memblock_dump_all();
>
>   	empty_zero_page = virt_to_page(zero_page);
>
> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> new file mode 100644
> index 0000000..604e886
> --- /dev/null
> +++ b/arch/arm64/mm/numa.c
> @@ -0,0 +1,403 @@
> +/*
> + * NUMA support, based on the x86 implementation.
> + *
> + * Copyright (C) 2015 Cavium Inc.
> + * Author: Ganapatrao Kulkarni <gkulkarni@cavium.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/bootmem.h>
> +#include <linux/memblock.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +
> +struct pglist_data *node_data[MAX_NUMNODES] __read_mostly;
> +EXPORT_SYMBOL(node_data);
> +nodemask_t numa_nodes_parsed __initdata;
> +static int cpu_to_node_map[NR_CPUS] = { [0 ... NR_CPUS-1] = NUMA_NO_NODE };
> +
> +static int numa_off;
> +static int numa_distance_cnt;
> +static u8 *numa_distance;
> +
> +static __init int numa_parse_early_param(char *opt)
> +{
> +	if (!opt)
> +		return -EINVAL;
> +	if (!strncmp(opt, "off", 3)) {
> +		pr_info("%s\n", "NUMA turned off");
> +		numa_off = 1;
> +	}
> +	return 0;
> +}
> +early_param("numa", numa_parse_early_param);
> +
> +cpumask_var_t node_to_cpumask_map[MAX_NUMNODES];
> +EXPORT_SYMBOL(node_to_cpumask_map);
> +
> +#ifdef CONFIG_DEBUG_PER_CPU_MAPS
> +
> +/*
> + * Returns a pointer to the bitmask of CPUs on Node 'node'.
> + */
> +const struct cpumask *cpumask_of_node(int node)
> +{
> +	if (WARN_ON(node >= nr_node_ids))
> +		return cpu_none_mask;
> +
> +	if (WARN_ON(node_to_cpumask_map[node] == NULL))
> +		return cpu_online_mask;
> +
> +	return node_to_cpumask_map[node];
> +}
> +EXPORT_SYMBOL(cpumask_of_node);
> +
> +#endif
> +
> +static void map_cpu_to_node(unsigned int cpu, int nid)
> +{
> +	set_cpu_numa_node(cpu, nid);
> +	if (nid >= 0)
> +		cpumask_set_cpu(cpu, node_to_cpumask_map[nid]);
> +}
> +
> +static void unmap_cpu_to_node(unsigned int cpu)
> +{
> +	int nid = cpu_to_node(cpu);
> +
> +	if (nid >= 0)
> +		cpumask_clear_cpu(cpu, node_to_cpumask_map[nid]);
> +	set_cpu_numa_node(cpu, NUMA_NO_NODE);
> +}
> +
> +void numa_clear_node(unsigned int cpu)
> +{
> +	unmap_cpu_to_node(cpu);
> +}
> +
> +/*
> + * Allocate node_to_cpumask_map based on number of available nodes
> + * Requires node_possible_map to be valid.
> + *
> + * Note: cpumask_of_node() is not valid until after this is done.
> + * (Use CONFIG_DEBUG_PER_CPU_MAPS to check this.)
> + */
> +static void __init setup_node_to_cpumask_map(void)
> +{
> +	unsigned int cpu;
> +	int node;
> +
> +	/* setup nr_node_ids if not done yet */
> +	if (nr_node_ids == MAX_NUMNODES)
> +		setup_nr_node_ids();
> +
> +	/* allocate and clear the mapping */
> +	for (node = 0; node < nr_node_ids; node++) {
> +		alloc_bootmem_cpumask_var(&node_to_cpumask_map[node]);
> +		cpumask_clear(node_to_cpumask_map[node]);
> +	}
> +
> +	for_each_possible_cpu(cpu)
> +		set_cpu_numa_node(cpu, NUMA_NO_NODE);
> +
> +	/* cpumask_of_node() will now work */
> +	pr_debug("NUMA: Node to cpumask map for %d nodes\n", nr_node_ids);
> +}
> +
> +/*
> + *  Set the cpu to node and mem mapping
> + */
> +void numa_store_cpu_info(unsigned int cpu)
> +{
> +	map_cpu_to_node(cpu, numa_off ? 0 : cpu_to_node_map[cpu]);
> +}
> +
> +void __init early_map_cpu_to_node(unsigned int cpu, int nid)
> +{
> +	/* fallback to node 0 */
> +	if (nid < 0 || nid >= MAX_NUMNODES)
> +		nid = 0;
> +
> +	cpu_to_node_map[cpu] = nid;
> +}
> +
> +/**
> + * numa_add_memblk - Set node id to memblk
> + * @nid: NUMA node ID of the new memblk
> + * @start: Start address of the new memblk
> + * @size:  Size of the new memblk
> + *
> + * RETURNS:
> + * 0 on success, -errno on failure.
> + */
> +int __init numa_add_memblk(int nid, u64 start, u64 size)
> +{
> +	int ret;
> +
> +	ret = memblock_set_node(start, size, &memblock.memory, nid);
> +	if (ret < 0) {
> +		pr_err("NUMA: memblock [0x%llx - 0x%llx] failed to add on node %d\n",
> +			start, (start + size - 1), nid);
> +		return ret;
> +	}
> +
> +	node_set(nid, numa_nodes_parsed);
> +	pr_info("NUMA: Adding memblock [0x%llx - 0x%llx] on node %d\n",
> +			start, (start + size - 1), nid);
> +	return ret;
> +}
> +EXPORT_SYMBOL(numa_add_memblk);
> +
> +/**
> + * Initialize NODE_DATA for a node on the local memory
> + */
> +static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
> +{
> +	const size_t nd_size = roundup(sizeof(pg_data_t), SMP_CACHE_BYTES);
> +	u64 nd_pa;
> +	void *nd;
> +	int tnid;
> +
> +	pr_info("NUMA: Initmem setup node %d [mem %#010Lx-%#010Lx]\n",
> +			nid, start_pfn << PAGE_SHIFT,
> +			(end_pfn << PAGE_SHIFT) - 1);
> +
> +	nd_pa = memblock_alloc_try_nid(nd_size, SMP_CACHE_BYTES, nid);
> +	nd = __va(nd_pa);
> +
> +	/* report and initialize */
> +	pr_info("NUMA: NODE_DATA [mem %#010Lx-%#010Lx]\n",
> +		nd_pa, nd_pa + nd_size - 1);
> +	tnid = early_pfn_to_nid(nd_pa >> PAGE_SHIFT);
> +	if (tnid != nid)
> +		pr_info("NUMA: NODE_DATA(%d) on node %d\n", nid, tnid);
> +
> +	node_data[nid] = nd;
> +	memset(NODE_DATA(nid), 0, sizeof(pg_data_t));
> +	NODE_DATA(nid)->node_id = nid;
> +	NODE_DATA(nid)->node_start_pfn = start_pfn;
> +	NODE_DATA(nid)->node_spanned_pages = end_pfn - start_pfn;
> +}
> +
> +/**
> + * numa_free_distance
> + *
> + * The current table is freed.
> + */
> +void __init numa_free_distance(void)
> +{
> +	size_t size;
> +
> +	if (!numa_distance)
> +		return;
> +
> +	size = numa_distance_cnt * numa_distance_cnt *
> +		sizeof(numa_distance[0]);
> +
> +	memblock_free(__pa(numa_distance), size);
> +	numa_distance_cnt = 0;
> +	numa_distance = NULL;
> +}
> +
> +/**
> + *
> + * Create a new NUMA distance table.
> + *
> + */
> +static int __init numa_alloc_distance(void)
> +{
> +	size_t size;
> +	u64 phys;
> +	int i, j;
> +
> +	size = nr_node_ids * nr_node_ids * sizeof(numa_distance[0]);
> +	phys = memblock_find_in_range(0, PFN_PHYS(max_pfn),
> +				      size, PAGE_SIZE);
> +	if (WARN_ON(!phys))
> +		return -ENOMEM;
> +
> +	memblock_reserve(phys, size);
> +
> +	numa_distance = __va(phys);
> +	numa_distance_cnt = nr_node_ids;
> +
> +	/* fill with the default distances */
> +	for (i = 0; i < numa_distance_cnt; i++)
> +		for (j = 0; j < numa_distance_cnt; j++)
> +			numa_distance[i * numa_distance_cnt + j] = i == j ?
> +				LOCAL_DISTANCE : REMOTE_DISTANCE;
> +
> +	pr_debug("NUMA: Initialized distance table, cnt=%d\n",
> +			numa_distance_cnt);
> +
> +	return 0;
> +}
> +
> +/**
> + * numa_set_distance - Set inter node NUMA distance from node to node.
> + * @from: the 'from' node to set distance
> + * @to: the 'to'  node to set distance
> + * @distance: NUMA distance
> + *
> + * Set the distance from node @from to @to to @distance.
> + * If distance table doesn't exist, a warning is printed.
> + *
> + * If @from or @to is higher than the highest known node or lower than zero
> + * or @distance doesn't make sense, the call is ignored.
> + *
> + */
> +void __init numa_set_distance(int from, int to, int distance)
> +{
> +	if (!numa_distance) {
> +		pr_warn_once("NUMA: Warning: distance table not allocated yet\n");
> +		return;
> +	}
> +
> +	if (from >= numa_distance_cnt || to >= numa_distance_cnt ||
> +			from < 0 || to < 0) {
> +		pr_warn_once("NUMA: Warning: node ids are out of bound, from=%d to=%d distance=%d\n",
> +			    from, to, distance);
> +		return;
> +	}
> +
> +	if ((u8)distance != distance ||
> +	    (from == to && distance != LOCAL_DISTANCE)) {
> +		pr_warn_once("NUMA: Warning: invalid distance parameter, from=%d to=%d distance=%d\n",
> +			     from, to, distance);
> +		return;
> +	}
> +
> +	numa_distance[from * numa_distance_cnt + to] = distance;
> +}
> +EXPORT_SYMBOL(numa_set_distance);
> +
> +/**
> + * Return NUMA distance @from to @to
> + */
> +int __node_distance(int from, int to)
> +{
> +	if (from >= numa_distance_cnt || to >= numa_distance_cnt)
> +		return from == to ? LOCAL_DISTANCE : REMOTE_DISTANCE;
> +	return numa_distance[from * numa_distance_cnt + to];
> +}
> +EXPORT_SYMBOL(__node_distance);
> +
> +static int __init numa_register_nodes(void)
> +{
> +	int nid;
> +	struct memblock_region *mblk;
> +
> +	/* Check that valid nid is set to memblks */
> +	for_each_memblock(memory, mblk)
> +		if (mblk->nid == NUMA_NO_NODE || mblk->nid >= MAX_NUMNODES) {
> +			pr_warn("NUMA: Warning: invalid memblk node %d [mem %#010Lx-%#010Lx]\n",
> +				mblk->nid, mblk->base,
> +				mblk->base + mblk->size - 1);
> +			return -EINVAL;
> +		}
> +
> +	/* Finally register nodes. */
> +	for_each_node_mask(nid, numa_nodes_parsed) {
> +		unsigned long start_pfn, end_pfn;
> +
> +		get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
> +		setup_node_data(nid, start_pfn, end_pfn);
> +		node_set_online(nid);
> +	}
> +
> +	/* Setup online nodes to actual nodes*/
> +	node_possible_map = numa_nodes_parsed;
> +
> +	return 0;
> +}
> +
> +static int __init numa_init(int (*init_func)(void))
> +{
> +	int ret;
> +
> +	nodes_clear(numa_nodes_parsed);
> +	nodes_clear(node_possible_map);
> +	nodes_clear(node_online_map);
> +	numa_free_distance();
> +
> +	ret = numa_alloc_distance();
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = init_func();
> +	if (ret < 0)
> +		return ret;
> +
> +	if (nodes_empty(numa_nodes_parsed))
> +		return -EINVAL;
> +
> +	ret = numa_register_nodes();
> +	if (ret < 0)
> +		return ret;
> +
> +	setup_node_to_cpumask_map();
> +
> +	/* init boot processor */
> +	cpu_to_node_map[0] = 0;
> +	map_cpu_to_node(0, 0);
> +
> +	return 0;
> +}
> +
> +/**
> + * dummy_numa_init - Fallback dummy NUMA init
> + *
> + * Used if there's no underlying NUMA architecture, NUMA initialization
> + * fails, or NUMA is disabled on the command line.
> + *
> + * Must online at least one node (node 0) and add memory blocks that cover all
> + * allowed memory. It is unlikely that this function fails.
> + */
> +static int __init dummy_numa_init(void)
> +{
> +	int ret;
> +	struct memblock_region *mblk;
> +
> +	pr_info("%s\n", "No NUMA configuration found");
> +	pr_info("NUMA: Faking a node at [mem %#018Lx-%#018Lx]\n",
> +	       0LLU, PFN_PHYS(max_pfn) - 1);
> +
> +	for_each_memblock(memory, mblk) {
> +		ret = numa_add_memblk(0, mblk->base, mblk->size);
> +		if (!ret)
> +			continue;
> +
> +		pr_err("NUMA init failed\n");
> +		return ret;
> +	}
> +
> +	numa_off = 1;
> +	return 0;
> +}
> +
> +/**
> + * arm64_numa_init - Initialize NUMA
> + *
> + * Try each configured NUMA initialization method until one succeeds.  The
> + * last fallback is dummy single node config encomapssing whole memory.
> + */
> +void __init arm64_numa_init(void)
> +{
> +	if (!numa_off) {
> +		if (!numa_init(of_numa_init))
> +			return;
> +	}
> +
> +	numa_init(dummy_numa_init);
> +}
>