arch/x86/kernel/setup_percpu.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/percpu.h>
#include <linux/kexec.h>
#include <linux/crash_dump.h>
#include <linux/smp.h>
#include <linux/topology.h>
#include <linux/pfn.h>
#include <asm/sections.h>
#include <asm/processor.h>
#include <asm/setup.h>
#include <asm/mpspec.h>
#include <asm/apicdef.h>
#include <asm/highmem.h>
#include <asm/proto.h>
#include <asm/cpumask.h>
#include <asm/cpu.h>
#include <asm/stackprotector.h>

#ifdef CONFIG_DEBUG_PER_CPU_MAPS
# define DBG(x...) printk(KERN_DEBUG x)
#else
# define DBG(x...)
#endif

DEFINE_PER_CPU(int, cpu_number);
EXPORT_PER_CPU_SYMBOL(cpu_number);

#ifdef CONFIG_X86_64
#define BOOT_PERCPU_OFFSET ((unsigned long)__per_cpu_load)
#else
#define BOOT_PERCPU_OFFSET 0
#endif

DEFINE_PER_CPU(unsigned long, this_cpu_off) = BOOT_PERCPU_OFFSET;
EXPORT_PER_CPU_SYMBOL(this_cpu_off);

unsigned long __per_cpu_offset[NR_CPUS] __read_mostly = {
	[0 ... NR_CPUS-1] = BOOT_PERCPU_OFFSET,
};
EXPORT_SYMBOL(__per_cpu_offset);

/*
 * On x86_64 symbols referenced from code should be reachable using
 * 32bit relocations.  Reserve space for static percpu variables in
 * modules so that they are always served from the first chunk which
 * is located at the percpu segment base.  On x86_32, anything can
 * address anywhere.  No need to reserve space in the first chunk.
 */
#ifdef CONFIG_X86_64
#define PERCPU_FIRST_CHUNK_RESERVE	PERCPU_MODULE_RESERVE
#else
#define PERCPU_FIRST_CHUNK_RESERVE	0
#endif

/**
 * pcpu_need_numa - determine percpu allocation needs to consider NUMA
 *
 * If NUMA is not configured or there is only one NUMA node available,
 * there is no reason to consider NUMA.  This function determines
 * whether percpu allocation should consider NUMA or not.
 *
 * RETURNS:
 * true if NUMA should be considered; otherwise, false.
 */
static bool __init pcpu_need_numa(void)
{
#ifdef CONFIG_NEED_MULTIPLE_NODES
	pg_data_t *last = NULL;
	unsigned int cpu;

	for_each_possible_cpu(cpu) {
		int node = early_cpu_to_node(cpu);

		if (node_online(node) && NODE_DATA(node) &&
		    last && last != NODE_DATA(node))
			return true;

		last = NODE_DATA(node);
	}
#endif
	return false;
}

/**
 * pcpu_alloc_bootmem - NUMA friendly alloc_bootmem wrapper for percpu
 * @cpu: cpu to allocate for
 * @size: size allocation in bytes
 * @align: alignment
 *
 * Allocate @size bytes aligned at @align for cpu @cpu.  This wrapper
 * does the right thing for NUMA regardless of the current
 * configuration.
 *
 * RETURNS:
 * Pointer to the allocated area on success, NULL on failure.
 */
static void * __init pcpu_alloc_bootmem(unsigned int cpu, unsigned long size,
					unsigned long align)
{
	const unsigned long goal = __pa(MAX_DMA_ADDRESS);
#ifdef CONFIG_NEED_MULTIPLE_NODES
	int node = early_cpu_to_node(cpu);
	void *ptr;

	if (!node_online(node) || !NODE_DATA(node)) {
		ptr = __alloc_bootmem_nopanic(size, align, goal);
		pr_info("cpu %d has no node %d or node-local memory\n",
			cpu, node);
		pr_debug("per cpu data for cpu%d %lu bytes at %016lx\n",
			 cpu, size, __pa(ptr));
	} else {
		ptr = __alloc_bootmem_node_nopanic(NODE_DATA(node),
						   size, align, goal);
		pr_debug("per cpu data for cpu%d %lu bytes on node%d at "
			 "%016lx\n", cpu, size, node, __pa(ptr));
	}
	return ptr;
#else
	return __alloc_bootmem_nopanic(size, align, goal);
#endif
}

/*
 * Helpers for first chunk memory allocation
 */
static void * __init pcpu_fc_alloc(unsigned int cpu, size_t size)
{
	return pcpu_alloc_bootmem(cpu, size, size);
}

static void __init pcpu_fc_free(void *ptr, size_t size)
{
	free_bootmem(__pa(ptr), size);
}

/*
 * Large page remap allocator
 *
 * This allocator uses PMD page as unit.  A PMD page is allocated for
 * each cpu and each is remapped into vmalloc area using PMD mapping.
 * As PMD page is quite large, only part of it is used for the first
 * chunk.  Unused part is returned to the bootmem allocator.
 *
 * So, the PMD pages are mapped twice - once to the physical mapping
 * and to the vmalloc area for the first percpu chunk.  The double
 * mapping does add one more PMD TLB entry pressure but still is much
 * better than only using 4k mappings while still being NUMA friendly.
 */
#ifdef CONFIG_NEED_MULTIPLE_NODES
struct pcpul_ent {
	unsigned int	cpu;
	void		*ptr;
};

static size_t pcpul_size;
static struct pcpul_ent *pcpul_map;
static struct vm_struct pcpul_vm;

static struct page * __init pcpul_get_page(unsigned int cpu, int pageno)
{
	size_t off = (size_t)pageno << PAGE_SHIFT;

	if (off >= pcpul_size)
		return NULL;

	return virt_to_page(pcpul_map[cpu].ptr + off);
}

static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
{
	size_t map_size, dyn_size;
	unsigned int cpu;
	int i, j;
	ssize_t ret;

	if (!chosen) {
		size_t vm_size = VMALLOC_END - VMALLOC_START;
		size_t tot_size = num_possible_cpus() * PMD_SIZE;

		/* on non-NUMA, embedding is better */
		if (!pcpu_need_numa())
			return -EINVAL;

		/* don't consume more than 20% of vmalloc area */
		if (tot_size > vm_size / 5) {
			pr_info("PERCPU: too large chunk size %zuMB for "
				"large page remap\n", tot_size >> 20);
			return -EINVAL;
		}
	}

	/* need PSE */
	if (!cpu_has_pse) {
		pr_warning("PERCPU: lpage allocator requires PSE\n");
		return -EINVAL;
	}

	/*
	 * Currently supports only single page.  Supporting multiple
	 * pages won't be too difficult if it ever becomes necessary.
	 */
	pcpul_size = PFN_ALIGN(static_size + PERCPU_MODULE_RESERVE +
			       PERCPU_DYNAMIC_RESERVE);
	if (pcpul_size > PMD_SIZE) {
		pr_warning("PERCPU: static data is larger than large page, "
			   "can't use large page\n");
		return -EINVAL;
	}
	dyn_size = pcpul_size - static_size - PERCPU_FIRST_CHUNK_RESERVE;

	/* allocate pointer array and alloc large pages */
	map_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpul_map[0]));
	pcpul_map = alloc_bootmem(map_size);

	for_each_possible_cpu(cpu) {
		pcpul_map[cpu].cpu = cpu;
		pcpul_map[cpu].ptr = pcpu_alloc_bootmem(cpu, PMD_SIZE,
							PMD_SIZE);
		if (!pcpul_map[cpu].ptr) {
			pr_warning("PERCPU: failed to allocate large page "
				   "for cpu%u\n", cpu);
			goto enomem;
		}

		/*
		 * Only use pcpul_size bytes and give back the rest.
		 *
		 * Ingo: The 2MB up-rounding bootmem is needed to make
		 * sure the partial 2MB page is still fully RAM - it's
		 * not well-specified to have a PAT-incompatible area
		 * (unmapped RAM, device memory, etc.) in that hole.
		 */
		free_bootmem(__pa(pcpul_map[cpu].ptr + pcpul_size),
			     PMD_SIZE - pcpul_size);

		memcpy(pcpul_map[cpu].ptr, __per_cpu_load, static_size);
	}

	/* allocate address and map */
	pcpul_vm.flags = VM_ALLOC;
	pcpul_vm.size = num_possible_cpus() * PMD_SIZE;
	vm_area_register_early(&pcpul_vm, PMD_SIZE);

	for_each_possible_cpu(cpu) {
		pmd_t *pmd, pmd_v;

		pmd = populate_extra_pmd((unsigned long)pcpul_vm.addr +
					 cpu * PMD_SIZE);
		pmd_v = pfn_pmd(page_to_pfn(virt_to_page(pcpul_map[cpu].ptr)),
				PAGE_KERNEL_LARGE);
		set_pmd(pmd, pmd_v);
	}

	/* we're ready, commit */
	pr_info("PERCPU: Remapped at %p with large pages, static data "
		"%zu bytes\n", pcpul_vm.addr, static_size);

	ret = pcpu_setup_first_chunk(pcpul_get_page, static_size,
				     PERCPU_FIRST_CHUNK_RESERVE, dyn_size,
				     PMD_SIZE, pcpul_vm.addr, NULL);

	/* sort pcpul_map array for pcpu_lpage_remapped() */
	for (i = 0; i < num_possible_cpus() - 1; i++)
		for (j = i + 1; j < num_possible_cpus(); j++)
			if (pcpul_map[i].ptr > pcpul_map[j].ptr) {
				struct pcpul_ent tmp = pcpul_map[i];
				pcpul_map[i] = pcpul_map[j];
				pcpul_map[j] = tmp;
			}

	return ret;

enomem:
	for_each_possible_cpu(cpu)
		if (pcpul_map[cpu].ptr)
			free_bootmem(__pa(pcpul_map[cpu].ptr), pcpul_size);
	free_bootmem(__pa(pcpul_map), map_size);
	return -ENOMEM;
}

/**
 * pcpu_lpage_remapped - determine whether a kaddr is in pcpul recycled area
 * @kaddr: the kernel address in question
 *
 * Determine whether @kaddr falls in the pcpul recycled area.  This is
 * used by pageattr to detect VM aliases and break up the pcpu PMD
 * mapping such that the same physical page is not mapped under
 * different attributes.
 *
 * The recycled area is always at the tail of a partially used PMD
 * page.
 *
 * RETURNS:
 * Address of corresponding remapped pcpu address if match is found;
 * otherwise, NULL.
 */
void *pcpu_lpage_remapped(void *kaddr)
{
	void *pmd_addr = (void *)((unsigned long)kaddr & PMD_MASK);
	unsigned long offset = (unsigned long)kaddr & ~PMD_MASK;
	int left = 0, right = num_possible_cpus() - 1;
	int pos;

	/* pcpul in use at all? */
	if (!pcpul_map)
		return NULL;

	/* okay, perform binary search */
	while (left <= right) {
		pos = (left + right) / 2;

		if (pcpul_map[pos].ptr < pmd_addr)
			left = pos + 1;
		else if (pcpul_map[pos].ptr > pmd_addr)
			right = pos - 1;
		else {
			/* it shouldn't be in the area for the first chunk */
			WARN_ON(offset < pcpul_size);

			return pcpul_vm.addr +
				pcpul_map[pos].cpu * PMD_SIZE + offset;
		}
	}

	return NULL;
}
#else
static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
{
	return -EINVAL;
}
#endif

/*
 * Embedding allocator
 *
 * The first chunk is sized to just contain the static area plus
 * module and dynamic reserves and embedded into linear physical
 * mapping so that it can use PMD mapping without additional TLB
 * pressure.
 */
static ssize_t __init setup_pcpu_embed(size_t static_size, bool chosen)
{
	size_t reserve = PERCPU_MODULE_RESERVE + PERCPU_DYNAMIC_RESERVE;

	/*
	 * If large page isn't supported, there's no benefit in doing
	 * this.  Also, embedding allocation doesn't play well with
	 * NUMA.
	 */
	if (!chosen && (!cpu_has_pse || pcpu_need_numa()))
		return -EINVAL;

	return pcpu_embed_first_chunk(static_size, PERCPU_FIRST_CHUNK_RESERVE,
				      reserve - PERCPU_FIRST_CHUNK_RESERVE);
}

/*
 * 4k allocator
 *
 * Boring fallback 4k allocator.  This allocator puts more pressure on
 * PTE TLBs but other than that behaves nicely on both UMA and NUMA.
 */
static void __init pcpu4k_populate_pte(unsigned long addr)
{
	populate_extra_pte(addr);
}

static ssize_t __init setup_pcpu_4k(size_t static_size)
{
	return pcpu_4k_first_chunk(static_size, PERCPU_FIRST_CHUNK_RESERVE,
				   pcpu_fc_alloc, pcpu_fc_free,
				   pcpu4k_populate_pte);
}

/* for explicit first chunk allocator selection */
static char pcpu_chosen_alloc[16] __initdata;

static int __init percpu_alloc_setup(char *str)
{
	strncpy(pcpu_chosen_alloc, str, sizeof(pcpu_chosen_alloc) - 1);
	return 0;
}
early_param("percpu_alloc", percpu_alloc_setup);

static inline void setup_percpu_segment(int cpu)
{
#ifdef CONFIG_X86_32
	struct desc_struct gdt;

	pack_descriptor(&gdt, per_cpu_offset(cpu), 0xFFFFF,
			0x2 | DESCTYPE_S, 0x8);
	gdt.s = 1;
	write_gdt_entry(get_cpu_gdt_table(cpu),
			GDT_ENTRY_PERCPU, &gdt, DESCTYPE_S);
#endif
}

void __init setup_per_cpu_areas(void)
{
	size_t static_size = __per_cpu_end - __per_cpu_start;
	unsigned int cpu;
	unsigned long delta;
	size_t pcpu_unit_size;
	ssize_t ret;

	pr_info("NR_CPUS:%d nr_cpumask_bits:%d nr_cpu_ids:%d nr_node_ids:%d\n",
		NR_CPUS, nr_cpumask_bits, nr_cpu_ids, nr_node_ids);

	/*
	 * Allocate percpu area.  If PSE is supported, try to make use
	 * of large page mappings.  Please read comments on top of
	 * each allocator for details.
	 */
	ret = -EINVAL;
	if (strlen(pcpu_chosen_alloc)) {
		if (strcmp(pcpu_chosen_alloc, "4k")) {
			if (!strcmp(pcpu_chosen_alloc, "lpage"))
				ret = setup_pcpu_lpage(static_size, true);
			else if (!strcmp(pcpu_chosen_alloc, "embed"))
				ret = setup_pcpu_embed(static_size, true);
			else
				pr_warning("PERCPU: unknown allocator %s "
					   "specified\n", pcpu_chosen_alloc);
			if (ret < 0)
				pr_warning("PERCPU: %s allocator failed (%zd), "
					   "falling back to 4k\n",
					   pcpu_chosen_alloc, ret);
		}
	} else {
		ret = setup_pcpu_lpage(static_size, false);
		if (ret < 0)
			ret = setup_pcpu_embed(static_size, false);
	}
	if (ret < 0)
		ret = setup_pcpu_4k(static_size);
	if (ret < 0)
		panic("cannot allocate static percpu area (%zu bytes, err=%zd)",
		      static_size, ret);

	pcpu_unit_size = ret;

	/* alrighty, percpu areas up and running */
	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
	for_each_possible_cpu(cpu) {
		per_cpu_offset(cpu) = delta + cpu * pcpu_unit_size;
		per_cpu(this_cpu_off, cpu) = per_cpu_offset(cpu);
		per_cpu(cpu_number, cpu) = cpu;
		setup_percpu_segment(cpu);
		setup_stack_canary_segment(cpu);
		/*
		 * Copy data used in early init routines from the
		 * initial arrays to the per cpu data areas.  These
		 * arrays then become expendable and the *_early_ptr's
		 * are zeroed indicating that the static arrays are
		 * gone.
		 */
#ifdef CONFIG_X86_LOCAL_APIC
		per_cpu(x86_cpu_to_apicid, cpu) =
			early_per_cpu_map(x86_cpu_to_apicid, cpu);
		per_cpu(x86_bios_cpu_apicid, cpu) =
			early_per_cpu_map(x86_bios_cpu_apicid, cpu);
#endif
#ifdef CONFIG_X86_64
		per_cpu(irq_stack_ptr, cpu) =
			per_cpu(irq_stack_union.irq_stack, cpu) +
			IRQ_STACK_SIZE - 64;
#ifdef CONFIG_NUMA
		per_cpu(x86_cpu_to_node_map, cpu) =
			early_per_cpu_map(x86_cpu_to_node_map, cpu);
#endif
#endif
		/*
		 * Up to this point, the boot CPU has been using .data.init
		 * area.  Reload any changed state for the boot CPU.
		 */
		if (cpu == boot_cpu_id)
			switch_to_new_gdt(cpu);
	}

	/* indicate the early static arrays will soon be gone */
#ifdef CONFIG_X86_LOCAL_APIC
	early_per_cpu_ptr(x86_cpu_to_apicid) = NULL;
	early_per_cpu_ptr(x86_bios_cpu_apicid) = NULL;
#endif
#if defined(CONFIG_X86_64) && defined(CONFIG_NUMA)
	early_per_cpu_ptr(x86_cpu_to_node_map) = NULL;
#endif

#if defined(CONFIG_X86_64) && defined(CONFIG_NUMA)
	/*
	 * make sure boot cpu node_number is right, when boot cpu is on the
	 * node that doesn't have mem installed
	 */
	per_cpu(node_number, boot_cpu_id) = cpu_to_node(boot_cpu_id);
#endif

	/* Setup node to cpumask map */
	setup_node_to_cpumask_map();

	/* Setup cpu initialized, callin, callout masks */
	setup_cpu_local_masks();
}