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/*
* Page table allocation functions
*
* Copyright IBM Corp. 2016
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#include <linux/mm.h>
#include <linux/sysctl.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>
#include <asm/gmap.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#ifdef CONFIG_PGSTE
static int page_table_allocate_pgste_min = 0;
static int page_table_allocate_pgste_max = 1;
int page_table_allocate_pgste = 0;
EXPORT_SYMBOL(page_table_allocate_pgste);
static struct ctl_table page_table_sysctl[] = {
{
.procname = "allocate_pgste",
.data = &page_table_allocate_pgste,
.maxlen = sizeof(int),
.mode = S_IRUGO | S_IWUSR,
.proc_handler = proc_dointvec,
.extra1 = &page_table_allocate_pgste_min,
.extra2 = &page_table_allocate_pgste_max,
},
{ }
};
static struct ctl_table page_table_sysctl_dir[] = {
{
.procname = "vm",
.maxlen = 0,
.mode = 0555,
.child = page_table_sysctl,
},
{ }
};
static int __init page_table_register_sysctl(void)
{
return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM;
}
__initcall(page_table_register_sysctl);
#endif /* CONFIG_PGSTE */
unsigned long *crst_table_alloc(struct mm_struct *mm)
{
struct page *page = alloc_pages(GFP_KERNEL, 2);
if (!page)
return NULL;
return (unsigned long *) page_to_phys(page);
}
void crst_table_free(struct mm_struct *mm, unsigned long *table)
{
free_pages((unsigned long) table, 2);
}
static void __crst_table_upgrade(void *arg)
{
struct mm_struct *mm = arg;
if (current->active_mm == mm) {
clear_user_asce();
set_user_asce(mm);
}
__tlb_flush_local();
}
int crst_table_upgrade(struct mm_struct *mm)
{
unsigned long *table, *pgd;
/* upgrade should only happen from 3 to 4 levels */
BUG_ON(mm->context.asce_limit != (1UL << 42));
table = crst_table_alloc(mm);
if (!table)
return -ENOMEM;
spin_lock_bh(&mm->page_table_lock);
pgd = (unsigned long *) mm->pgd;
crst_table_init(table, _REGION2_ENTRY_EMPTY);
pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd);
mm->pgd = (pgd_t *) table;
mm->context.asce_limit = 1UL << 53;
mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS | _ASCE_TYPE_REGION2;
mm->task_size = mm->context.asce_limit;
spin_unlock_bh(&mm->page_table_lock);
on_each_cpu(__crst_table_upgrade, mm, 0);
return 0;
}
void crst_table_downgrade(struct mm_struct *mm)
{
pgd_t *pgd;
/* downgrade should only happen from 3 to 2 levels (compat only) */
BUG_ON(mm->context.asce_limit != (1UL << 42));
if (current->active_mm == mm) {
clear_user_asce();
__tlb_flush_mm(mm);
}
pgd = mm->pgd;
mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
mm->context.asce_limit = 1UL << 31;
mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
mm->task_size = mm->context.asce_limit;
crst_table_free(mm, (unsigned long *) pgd);
if (current->active_mm == mm)
set_user_asce(mm);
}
static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
{
unsigned int old, new;
do {
old = atomic_read(v);
new = old ^ bits;
} while (atomic_cmpxchg(v, old, new) != old);
return new;
}
/*
* page table entry allocation/free routines.
*/
unsigned long *page_table_alloc(struct mm_struct *mm)
{
unsigned long *table;
struct page *page;
unsigned int mask, bit;
/* Try to get a fragment of a 4K page as a 2K page table */
if (!mm_alloc_pgste(mm)) {
table = NULL;
spin_lock_bh(&mm->context.list_lock);
if (!list_empty(&mm->context.pgtable_list)) {
page = list_first_entry(&mm->context.pgtable_list,
struct page, lru);
mask = atomic_read(&page->_mapcount);
mask = (mask | (mask >> 4)) & 3;
if (mask != 3) {
table = (unsigned long *) page_to_phys(page);
bit = mask & 1; /* =1 -> second 2K */
if (bit)
table += PTRS_PER_PTE;
atomic_xor_bits(&page->_mapcount, 1U << bit);
list_del(&page->lru);
}
}
spin_unlock_bh(&mm->context.list_lock);
if (table)
return table;
}
/* Allocate a fresh page */
page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
if (!page)
return NULL;
if (!pgtable_page_ctor(page)) {
__free_page(page);
return NULL;
}
/* Initialize page table */
table = (unsigned long *) page_to_phys(page);
if (mm_alloc_pgste(mm)) {
/* Return 4K page table with PGSTEs */
atomic_set(&page->_mapcount, 3);
clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
} else {
/* Return the first 2K fragment of the page */
atomic_set(&page->_mapcount, 1);
clear_table(table, _PAGE_INVALID, PAGE_SIZE);
spin_lock_bh(&mm->context.list_lock);
list_add(&page->lru, &mm->context.pgtable_list);
spin_unlock_bh(&mm->context.list_lock);
}
return table;
}
void page_table_free(struct mm_struct *mm, unsigned long *table)
{
struct page *page;
unsigned int bit, mask;
page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
if (!mm_alloc_pgste(mm)) {
/* Free 2K page table fragment of a 4K page */
bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
spin_lock_bh(&mm->context.list_lock);
mask = atomic_xor_bits(&page->_mapcount, 1U << bit);
if (mask & 3)
list_add(&page->lru, &mm->context.pgtable_list);
else
list_del(&page->lru);
spin_unlock_bh(&mm->context.list_lock);
if (mask != 0)
return;
}
pgtable_page_dtor(page);
atomic_set(&page->_mapcount, -1);
__free_page(page);
}
void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
unsigned long vmaddr)
{
struct mm_struct *mm;
struct page *page;
unsigned int bit, mask;
mm = tlb->mm;
page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
if (mm_alloc_pgste(mm)) {
gmap_unlink(mm, table, vmaddr);
table = (unsigned long *) (__pa(table) | 3);
tlb_remove_table(tlb, table);
return;
}
bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
spin_lock_bh(&mm->context.list_lock);
mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit);
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