s390/mm: remove fake numa support

It turned out that fake numa support is rather useless on s390, since
there are no scenarios where there is any performance or other benefit
when used.

However it does provide maintenance cost and breaks from time to time.
Therefore remove it.

CONFIG_NUMA is still supported with a very small backend and only one
node. This way userspace applications which require NUMA interfaces
continue to work.

Note that NODES_SHIFT is set to 1 (= 2 nodes) instead of 0 (= 1 node),
since there is quite a bit of kernel code which assumes that more than
one node is possible if CONFIG_NUMA is enabled.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 0 insertions, 577 deletions

diff --git a/arch/s390/numa/mode_emu.c b/arch/s390/numa/mode_emu.c
deleted file mode 100644
index 72d742bb2d17..000000000000
--- a/arch/s390/numa/mode_emu.c
+++ /dev/null
@@ -1,577 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * NUMA support for s390
- *
- * NUMA emulation (aka fake NUMA) distributes the available memory to nodes
- * without using real topology information about the physical memory of the
- * machine.
- *
- * It distributes the available CPUs to nodes while respecting the original
- * machine topology information. This is done by trying to avoid to separate
- * CPUs which reside on the same book or even on the same MC.
- *
- * Because the current Linux scheduler code requires a stable cpu to node
- * mapping, cores are pinned to nodes when the first CPU thread is set online.
- *
- * Copyright IBM Corp. 2015
- */
-
-#define KMSG_COMPONENT "numa_emu"
-#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
-
-#include <linux/kernel.h>
-#include <linux/cpumask.h>
-#include <linux/memblock.h>
-#include <linux/node.h>
-#include <linux/memory.h>
-#include <linux/slab.h>
-#include <asm/smp.h>
-#include <asm/topology.h>
-#include "numa_mode.h"
-#include "toptree.h"
-
-/* Distances between the different system components */
-#define DIST_EMPTY	0
-#define DIST_CORE	1
-#define DIST_MC		2
-#define DIST_BOOK	3
-#define DIST_DRAWER	4
-#define DIST_MAX	5
-
-/* Node distance reported to common code */
-#define EMU_NODE_DIST	10
-
-/* Node ID for free (not yet pinned) cores */
-#define NODE_ID_FREE	-1
-
-/* Different levels of toptree */
-enum toptree_level {CORE, MC, BOOK, DRAWER, NODE, TOPOLOGY};
-
-/* The two toptree IDs */
-enum {TOPTREE_ID_PHYS, TOPTREE_ID_NUMA};
-
-/* Number of NUMA nodes */
-static int emu_nodes = 1;
-/* NUMA stripe size */
-static unsigned long emu_size;
-
-/*
- * Node to core pinning information updates are protected by
- * "sched_domains_mutex".
- */
-static struct {
-	s32 to_node_id[CONFIG_NR_CPUS];	/* Pinned core to node mapping */
-	int total;			/* Total number of pinned cores */
-	int per_node_target;		/* Cores per node without extra cores */
-	int per_node[MAX_NUMNODES];	/* Number of cores pinned to node */
-} *emu_cores;
-
-/*
- * Pin a core to a node
- */
-static void pin_core_to_node(int core_id, int node_id)
-{
-	if (emu_cores->to_node_id[core_id] == NODE_ID_FREE) {
-		emu_cores->per_node[node_id]++;
-		emu_cores->to_node_id[core_id] = node_id;
-		emu_cores->total++;
-	} else {
-		WARN_ON(emu_cores->to_node_id[core_id] != node_id);
-	}
-}
-
-/*
- * Number of pinned cores of a node
- */
-static int cores_pinned(struct toptree *node)
-{
-	return emu_cores->per_node[node->id];
-}
-
-/*
- * ID of the node where the core is pinned (or NODE_ID_FREE)
- */
-static int core_pinned_to_node_id(struct toptree *core)
-{
-	return emu_cores->to_node_id[core->id];
-}
-
-/*
- * Number of cores in the tree that are not yet pinned
- */
-static int cores_free(struct toptree *tree)
-{
-	struct toptree *core;
-	int count = 0;
-
-	toptree_for_each(core, tree, CORE) {
-		if (core_pinned_to_node_id(core) == NODE_ID_FREE)
-			count++;
-	}
-	return count;
-}
-
-/*
- * Return node of core
- */
-static struct toptree *core_node(struct toptree *core)
-{
-	return core->parent->parent->parent->parent;
-}
-
-/*
- * Return drawer of core
- */
-static struct toptree *core_drawer(struct toptree *core)
-{
-	return core->parent->parent->parent;
-}
-
-/*
- * Return book of core
- */
-static struct toptree *core_book(struct toptree *core)
-{
-	return core->parent->parent;
-}
-
-/*
- * Return mc of core
- */
-static struct toptree *core_mc(struct toptree *core)
-{
-	return core->parent;
-}
-
-/*
- * Distance between two cores
- */
-static int dist_core_to_core(struct toptree *core1, struct toptree *core2)
-{
-	if (core_drawer(core1)->id != core_drawer(core2)->id)
-		return DIST_DRAWER;
-	if (core_book(core1)->id != core_book(core2)->id)
-		return DIST_BOOK;
-	if (core_mc(core1)->id != core_mc(core2)->id)
-		return DIST_MC;
-	/* Same core or sibling on same MC */
-	return DIST_CORE;
-}
-
-/*
- * Distance of a node to a core
- */
-static int dist_node_to_core(struct toptree *node, struct toptree *core)
-{
-	struct toptree *core_node;
-	int dist_min = DIST_MAX;
-
-	toptree_for_each(core_node, node, CORE)
-		dist_min = min(dist_min, dist_core_to_core(core_node, core));
-	return dist_min == DIST_MAX ? DIST_EMPTY : dist_min;
-}
-
-/*
- * Unify will delete empty nodes, therefore recreate nodes.
- */
-static void toptree_unify_tree(struct toptree *tree)
-{
-	int nid;
-
-	toptree_unify(tree);
-	for (nid = 0; nid < emu_nodes; nid++)
-		toptree_get_child(tree, nid);
-}
-
-/*
- * Find the best/nearest node for a given core and ensure that no node
- * gets more than "emu_cores->per_node_target + extra" cores.
- */
-static struct toptree *node_for_core(struct toptree *numa, struct toptree *core,
-				     int extra)
-{
-	struct toptree *node, *node_best = NULL;
-	int dist_cur, dist_best, cores_target;
-
-	cores_target = emu_cores->per_node_target + extra;
-	dist_best = DIST_MAX;
-	node_best = NULL;
-	toptree_for_each(node, numa, NODE) {
-		/* Already pinned cores must use their nodes */
-		if (core_pinned_to_node_id(core) == node->id) {
-			node_best = node;
-			break;
-		}
-		/* Skip nodes that already have enough cores */
-		if (cores_pinned(node) >= cores_target)
-			continue;
-		dist_cur = dist_node_to_core(node, core);
-		if (dist_cur < dist_best) {
-			dist_best = dist_cur;
-			node_best = node;
-		}
-	}
-	return node_best;
-}
-
-/*
- * Find the best node for each core with respect to "extra" core count
- */
-static void toptree_to_numa_single(struct toptree *numa, struct toptree *phys,
-				   int extra)
-{
-	struct toptree *node, *core, *tmp;
-
-	toptree_for_each_safe(core, tmp, phys, CORE) {
-		node = node_for_core(numa, core, extra);
-		if (!node)
-			return;
-		toptree_move(core, node);
-		pin_core_to_node(core->id, node->id);
-	}
-}
-
-/*
- * Move structures of given level to specified NUMA node
- */
-static void move_level_to_numa_node(struct toptree *node, struct toptree *phys,
-				    enum toptree_level level, bool perfect)
-{
-	int cores_free, cores_target = emu_cores->per_node_target;
-	struct toptree *cur, *tmp;
-
-	toptree_for_each_safe(cur, tmp, phys, level) {
-		cores_free = cores_target - toptree_count(node, CORE);
-		if (perfect) {
-			if (cores_free == toptree_count(cur, CORE))
-				toptree_move(cur, node);
-		} else {
-			if (cores_free >= toptree_count(cur, CORE))
-				toptree_move(cur, node);
-		}
-	}
-}
-
-/*
- * Move structures of a given level to NUMA nodes. If "perfect" is specified
- * move only perfectly fitting structures. Otherwise move also smaller
- * than needed structures.
- */
-static void move_level_to_numa(struct toptree *numa, struct toptree *phys,
-			       enum toptree_level level, bool perfect)
-{
-	struct toptree *node;
-
-	toptree_for_each(node, numa, NODE)
-		move_level_to_numa_node(node, phys, level, perfect);
-}
-
-/*
- * For the first run try to move the big structures
- */
-static void toptree_to_numa_first(struct toptree *numa, struct toptree *phys)
-{
-	struct toptree *core;
-
-	/* Always try to move perfectly fitting structures first */
-	move_level_to_numa(numa, phys, DRAWER, true);
-	move_level_to_numa(numa, phys, DRAWER, false);
-	move_level_to_numa(numa, phys, BOOK, true);
-	move_level_to_numa(numa, phys, BOOK, false);
-	move_level_to_numa(numa, phys, MC, true);
-	move_level_to_numa(numa, phys, MC, false);
-	/* Now pin all the moved cores */
-	toptree_for_each(core, numa, CORE)
-		pin_core_to_node(core->id, core_node(core)->id);
-}
-
-/*
- * Allocate new topology and create required nodes
- */
-static struct toptree *toptree_new(int id, int nodes)
-{
-	struct toptree *tree;
-	int nid;
-
-	tree = toptree_alloc(TOPOLOGY, id);
-	if (!tree)
-		goto fail;
-	for (nid = 0; nid < nodes; nid++) {
-		if (!toptree_get_child(tree, nid))
-			goto fail;
-	}
-	return tree;
-fail:
-	panic("NUMA emulation could not allocate topology");
-}
-
-/*
- * Allocate and initialize core to node mapping
- */
-static void __ref create_core_to_node_map(void)
-{
-	int i;
-
-	emu_cores = memblock_alloc(sizeof(*emu_cores), 8);
-	if (!emu_cores)
-		panic("%s: Failed to allocate %zu bytes align=0x%x\n",
-		      __func__, sizeof(*emu_cores), 8);
-	for (i = 0; i < ARRAY_SIZE(emu_cores->to_node_id); i++)
-		emu_cores->to_node_id[i] = NODE_ID_FREE;
-}
-
-/*
- * Move cores from physical topology into NUMA target topology
- * and try to keep as much of the physical topology as possible.
- */
-static struct toptree *toptree_to_numa(struct toptree *phys)
-{
-	static int first = 1;
-	struct toptree *numa;
-	int cores_total;
-
-	cores_total = emu_cores->total + cores_free(phys);
-	emu_cores->per_node_target = cores_total / emu_nodes;
-	numa = toptree_new(TOPTREE_ID_NUMA, emu_nodes);
-	if (first) {
-		toptree_to_numa_first(numa, phys);
-		first = 0;
-	}
-	toptree_to_numa_single(numa, phys, 0);
-	toptree_to_numa_single(numa, phys, 1);
-	toptree_unify_tree(numa);
-
-	WARN_ON(cpumask_weight(&phys->mask));
-	return numa;
-}
-
-/*
- * Create a toptree out of the physical topology that we got from the hypervisor
- */
-static struct toptree *toptree_from_topology(void)
-{
-	struct toptree *phys, *node, *drawer, *book, *mc, *core;
-	struct cpu_topology_s390 *top;
-	int cpu;
-
-	phys = toptree_new(TOPTREE_ID_PHYS, 1);
-
-	for_each_cpu(cpu, &cpus_with_topology) {
-		top = &cpu_topology[cpu];
-		node = toptree_get_child(phys, 0);
-		drawer = toptree_get_child(node, top->drawer_id);
-		book = toptree_get_child(drawer, top->book_id);
-		mc = toptree_get_child(book, top->socket_id);
-		core = toptree_get_child(mc, smp_get_base_cpu(cpu));
-		if (!drawer || !book || !mc || !core)
-			panic("NUMA emulation could not allocate memory");
-		cpumask_set_cpu(cpu, &core->mask);
-		toptree_update_mask(mc);
-	}
-	return phys;
-}
-
-/*
- * Add toptree core to topology and create correct CPU masks
- */
-static void topology_add_core(struct toptree *core)
-{
-	struct cpu_topology_s390 *top;
-	int cpu;
-
-	for_each_cpu(cpu, &core->mask) {
-		top = &cpu_topology[cpu];
-		cpumask_copy(&top->thread_mask, &core->mask);
-		cpumask_copy(&top->core_mask, &core_mc(core)->mask);
-		cpumask_copy(&top->book_mask, &core_book(core)->mask);
-		cpumask_copy(&top->drawer_mask, &core_drawer(core)->mask);
-		cpumask_set_cpu(cpu, &node_to_cpumask_map[core_node(core)->id]);
-		top->node_id = core_node(core)->id;
-	}
-}
-
-/*
- * Apply toptree to topology and create CPU masks
- */
-static void toptree_to_topology(struct toptree *numa)
-{
-	struct toptree *core;
-	int i;
-
-	/* Clear all node masks */
-	for (i = 0; i < MAX_NUMNODES; i++)
-		cpumask_clear(&node_to_cpumask_map[i]);
-
-	/* Rebuild all masks */
-	toptree_for_each(core, numa, CORE)
-		topology_add_core(core);
-}
-
-/*
- * Show the node to core mapping
- */
-static void print_node_to_core_map(void)
-{
-	int nid, cid;
-
-	if (!numa_debug_enabled)
-		return;
-	printk(KERN_DEBUG "NUMA node to core mapping\n");
-	for (nid = 0; nid < emu_nodes; nid++) {
-		printk(KERN_DEBUG "  node %3d: ", nid);
-		for (cid = 0; cid < ARRAY_SIZE(emu_cores->to_node_id); cid++) {
-			if (emu_cores->to_node_id[cid] == nid)
-				printk(KERN_CONT "%d ", cid);
-		}
-		printk(KERN_CONT "\n");
-	}
-}
-
-static void pin_all_possible_cpus(void)
-{
-	int core_id, node_id, cpu;
-	static int initialized;
-
-	if (initialized)
-		return;
-	print_node_to_core_map();
-	node_id = 0;
-	for_each_possible_cpu(cpu) {
-		core_id = smp_get_base_cpu(cpu);
-		if (emu_cores->to_node_id[core_id] != NODE_ID_FREE)
-			continue;
-		pin_core_to_node(core_id, node_id);
-		cpu_topology[cpu].node_id = node_id;
-		node_id = (node_id + 1) % emu_nodes;
-	}
-	print_node_to_core_map();
-	initialized = 1;
-}
-
-/*
- * Transfer physical topology into a NUMA topology and modify CPU masks
- * according to the NUMA topology.
- *
- * Must be called with "sched_domains_mutex" lock held.
- */
-static void emu_update_cpu_topology(void)
-{
-	struct toptree *phys, *numa;
-
-	if (emu_cores == NULL)
-		create_core_to_node_map();
-	phys = toptree_from_topology();
-	numa = toptree_to_numa(phys);
-	toptree_free(phys);
-	toptree_to_topology(numa);
-	toptree_free(numa);
-	pin_all_possible_cpus();
-}
-
-/*
- * If emu_size is not set, use CONFIG_EMU_SIZE. Then round to minimum
- * alignment (needed for memory hotplug).
- */
-static unsigned long emu_setup_size_adjust(unsigned long size)
-{
-	unsigned long size_new;
-
-	size = size ? : CONFIG_EMU_SIZE;
-	size_new = roundup(size, memory_block_size_bytes());
-	if (size_new == size)
-		return size;
-	pr_warn("Increasing memory stripe size from %ld MB to %ld MB\n",
-		size >> 20, size_new >> 20);
-	return size_new;
-}
-
-/*
- * If we have not enough memory for the specified nodes, reduce the node count.
- */
-static int emu_setup_nodes_adjust(int nodes)
-{
-	int nodes_max;
-
-	nodes_max = memblock.memory.total_size / emu_size;
-	nodes_max = max(nodes_max, 1);
-	if (nodes_max >= nodes)
-		return nodes;
-	pr_warn("Not enough memory for %d nodes, reducing node count\n", nodes);
-	return nodes_max;
-}
-
-/*
- * Early emu setup
- */
-static void emu_setup(void)
-{
-	int nid;
-
-	emu_size = emu_setup_size_adjust(emu_size);
-	emu_nodes = emu_setup_nodes_adjust(emu_nodes);
-	for (nid = 0; nid < emu_nodes; nid++)
-		node_set(nid, node_possible_map);
-	pr_info("Creating %d nodes with memory stripe size %ld MB\n",
-		emu_nodes, emu_size >> 20);
-}
-
-/*
- * Return node id for given page number
- */
-static int emu_pfn_to_nid(unsigned long pfn)
-{
-	return (pfn / (emu_size >> PAGE_SHIFT)) % emu_nodes;
-}
-
-/*
- * Return stripe size
- */
-static unsigned long emu_align(void)
-{
-	return emu_size;
-}
-
-/*
- * Return distance between two nodes
- */
-static int emu_distance(int node1, int node2)
-{
-	return (node1 != node2) * EMU_NODE_DIST;
-}
-
-/*
- * Define callbacks for generic s390 NUMA infrastructure
- */
-const struct numa_mode numa_mode_emu = {
-	.name = "emu",
-	.setup = emu_setup,
-	.update_cpu_topology = emu_update_cpu_topology,
-	.__pfn_to_nid = emu_pfn_to_nid,
-	.align = emu_align,
-	.distance = emu_distance,
-};
-
-/*
- * Kernel parameter: emu_nodes=<n>
- */
-static int __init early_parse_emu_nodes(char *p)
-{
-	int count;
-
-	if (!p || kstrtoint(p, 0, &count) != 0 || count <= 0)
-		return 0;
-	emu_nodes = min(count, MAX_NUMNODES);
-	return 0;
-}
-early_param("emu_nodes", early_parse_emu_nodes);
-
-/*
- * Kernel parameter: emu_size=[<n>[k|M|G|T]]
- */
-static int __init early_parse_emu_size(char *p)
-{
-	if (p)
-		emu_size = memparse(p, NULL);
-	return 0;
-}
-early_param("emu_size", early_parse_emu_size);