// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
* Handling Page Tables through page fragments
|
*
|
*/
|
|
#include <linux/kernel.h>
|
#include <linux/gfp.h>
|
#include <linux/mm.h>
|
#include <linux/percpu.h>
|
#include <linux/hardirq.h>
|
#include <linux/hugetlb.h>
|
#include <asm/pgalloc.h>
|
#include <asm/tlbflush.h>
|
#include <asm/tlb.h>
|
|
void pte_frag_destroy(void *pte_frag)
|
{
|
int count;
|
struct page *page;
|
|
page = virt_to_page(pte_frag);
|
/* drop all the pending references */
|
count = ((unsigned long)pte_frag & ~PAGE_MASK) >> PTE_FRAG_SIZE_SHIFT;
|
/* We allow PTE_FRAG_NR fragments from a PTE page */
|
if (atomic_sub_and_test(PTE_FRAG_NR - count, &page->pt_frag_refcount)) {
|
pgtable_pte_page_dtor(page);
|
__free_page(page);
|
}
|
}
|
|
static pte_t *get_pte_from_cache(struct mm_struct *mm)
|
{
|
void *pte_frag, *ret;
|
|
if (PTE_FRAG_NR == 1)
|
return NULL;
|
|
spin_lock(&mm->page_table_lock);
|
ret = pte_frag_get(&mm->context);
|
if (ret) {
|
pte_frag = ret + PTE_FRAG_SIZE;
|
/*
|
* If we have taken up all the fragments mark PTE page NULL
|
*/
|
if (((unsigned long)pte_frag & ~PAGE_MASK) == 0)
|
pte_frag = NULL;
|
pte_frag_set(&mm->context, pte_frag);
|
}
|
spin_unlock(&mm->page_table_lock);
|
return (pte_t *)ret;
|
}
|
|
static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel)
|
{
|
void *ret = NULL;
|
struct page *page;
|
|
if (!kernel) {
|
page = alloc_page(PGALLOC_GFP | __GFP_ACCOUNT);
|
if (!page)
|
return NULL;
|
if (!pgtable_pte_page_ctor(page)) {
|
__free_page(page);
|
return NULL;
|
}
|
} else {
|
page = alloc_page(PGALLOC_GFP);
|
if (!page)
|
return NULL;
|
}
|
|
atomic_set(&page->pt_frag_refcount, 1);
|
|
ret = page_address(page);
|
/*
|
* if we support only one fragment just return the
|
* allocated page.
|
*/
|
if (PTE_FRAG_NR == 1)
|
return ret;
|
spin_lock(&mm->page_table_lock);
|
/*
|
* If we find pgtable_page set, we return
|
* the allocated page with single fragement
|
* count.
|
*/
|
if (likely(!pte_frag_get(&mm->context))) {
|
atomic_set(&page->pt_frag_refcount, PTE_FRAG_NR);
|
pte_frag_set(&mm->context, ret + PTE_FRAG_SIZE);
|
}
|
spin_unlock(&mm->page_table_lock);
|
|
return (pte_t *)ret;
|
}
|
|
pte_t *pte_fragment_alloc(struct mm_struct *mm, int kernel)
|
{
|
pte_t *pte;
|
|
pte = get_pte_from_cache(mm);
|
if (pte)
|
return pte;
|
|
return __alloc_for_ptecache(mm, kernel);
|
}
|
|
void pte_fragment_free(unsigned long *table, int kernel)
|
{
|
struct page *page = virt_to_page(table);
|
|
if (PageReserved(page))
|
return free_reserved_page(page);
|
|
BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0);
|
if (atomic_dec_and_test(&page->pt_frag_refcount)) {
|
if (!kernel)
|
pgtable_pte_page_dtor(page);
|
__free_page(page);
|
}
|
}
|
