Commit eb553f16 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Michael Ellerman
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powerpc/64/mm: implement page mapping percpu first chunk allocator 



Implement page mapping percpu first chunk allocator as a fallback to
the embedding allocator. With 4K hash translation we limit our page
table range to 64TB and commit: 0034d395 ("powerpc/mm/hash64: Map all the
kernel regions in the same 0xc range") moved all kernel mapping to
that 64TB range. In-order to support sparse memory layout we need
to increase our linear mapping space and reduce other mappings.

With such a layout percpu embedded first chunk allocator will fail
because of small vmalloc range. Add a fallback to page mapping
percpu first chunk allocator for such failures.

The below dmesg output can be observed in such case.

 percpu: max_distance=0x1ffffef00000 too large for vmalloc space 0x10000000000
 PERCPU: auto allocator failed (-22), falling back to page size
 percpu: 40 4K pages/cpu s148816 r0 d15024

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200608070904.387440-2-aneesh.kumar@linux.ibm.com
parent 2a32abac

arch/powerpc/Kconfig

+4 −1
Original line number Diff line number Diff line
@@ -59,7 +59,10 @@ config HAVE_SETUP_PER_CPU_AREA 
	def_bool PPC64



config NEED_PER_CPU_EMBED_FIRST_CHUNK

	def_bool PPC64

	def_bool y if PPC64



config NEED_PER_CPU_PAGE_FIRST_CHUNK

	def_bool y if PPC64



config NR_IRQS

	int "Number of virtual interrupt numbers"

arch/powerpc/kernel/setup_64.c

+59 −3
Original line number Diff line number Diff line
@@ -66,6 +66,7 @@ 
#include <asm/feature-fixups.h>

#include <asm/kup.h>

#include <asm/early_ioremap.h>

#include <asm/pgalloc.h>



#include "setup.h"
@@ -811,13 +812,58 @@ static int pcpu_cpu_distance(unsigned int from, unsigned int to) 
unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;

EXPORT_SYMBOL(__per_cpu_offset);



static void __init pcpu_populate_pte(unsigned long addr)

{

	pgd_t *pgd = pgd_offset_k(addr);

	p4d_t *p4d;

	pud_t *pud;

	pmd_t *pmd;



	p4d = p4d_offset(pgd, addr);

	if (p4d_none(*p4d)) {

		pud_t *new;



		new = memblock_alloc(PUD_TABLE_SIZE, PUD_TABLE_SIZE);

		if (!new)

			goto err_alloc;

		p4d_populate(&init_mm, p4d, new);

	}



	pud = pud_offset(p4d, addr);

	if (pud_none(*pud)) {

		pmd_t *new;



		new = memblock_alloc(PMD_TABLE_SIZE, PMD_TABLE_SIZE);

		if (!new)

			goto err_alloc;

		pud_populate(&init_mm, pud, new);

	}



	pmd = pmd_offset(pud, addr);

	if (!pmd_present(*pmd)) {

		pte_t *new;



		new = memblock_alloc(PTE_TABLE_SIZE, PTE_TABLE_SIZE);

		if (!new)

			goto err_alloc;

		pmd_populate_kernel(&init_mm, pmd, new);

	}



	return;



err_alloc:

	panic("%s: Failed to allocate %lu bytes align=%lx from=%lx\n",

	      __func__, PAGE_SIZE, PAGE_SIZE, PAGE_SIZE);

}





void __init setup_per_cpu_areas(void)

{

	const size_t dyn_size = PERCPU_MODULE_RESERVE + PERCPU_DYNAMIC_RESERVE;

	size_t atom_size;

	unsigned long delta;

	unsigned int cpu;

	int rc;

	int rc = -EINVAL;



	/*

	 * Linear mapping is one of 4K, 1M and 16M.  For 4K, no need
@@ -829,8 +875,18 @@ void __init setup_per_cpu_areas(void) 
	else

		atom_size = 1 << 20;



	if (pcpu_chosen_fc != PCPU_FC_PAGE) {

		rc = pcpu_embed_first_chunk(0, dyn_size, atom_size, pcpu_cpu_distance,

					    pcpu_alloc_bootmem, pcpu_free_bootmem);

		if (rc)

			pr_warn("PERCPU: %s allocator failed (%d), "

				"falling back to page size\n",

				pcpu_fc_names[pcpu_chosen_fc], rc);

	}



	if (rc < 0)

		rc = pcpu_page_first_chunk(0, pcpu_alloc_bootmem, pcpu_free_bootmem,

					   pcpu_populate_pte);

	if (rc < 0)

		panic("cannot initialize percpu area (err=%d)", rc);

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