swh:1:snp:49cd9498d6cccc5e78252c27dcb645bcf7bf0c91
Tip revision: 9abf2313adc1ca1b6180c508c25f22f9395cc780 authored by Linus Torvalds on 16 October 2022, 22:36:24 UTC
Linux 6.1-rc1
Linux 6.1-rc1
Tip revision: 9abf231
pgalloc.c
// SPDX-License-Identifier: GPL-2.0
/*
* Page table allocation functions
*
* Copyright IBM Corp. 2016
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#include <linux/sysctl.h>
#include <linux/slab.h>
#include <linux/mm.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
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_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
{ }
};
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, CRST_ALLOC_ORDER);
if (!page)
return NULL;
arch_set_page_dat(page, CRST_ALLOC_ORDER);
return (unsigned long *) page_to_virt(page);
}
void crst_table_free(struct mm_struct *mm, unsigned long *table)
{
free_pages((unsigned long)table, CRST_ALLOC_ORDER);
}
static void __crst_table_upgrade(void *arg)
{
struct mm_struct *mm = arg;
/* change all active ASCEs to avoid the creation of new TLBs */
if (current->active_mm == mm) {
S390_lowcore.user_asce = mm->context.asce;
__ctl_load(S390_lowcore.user_asce, 7, 7);
}
__tlb_flush_local();
}
int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
{
unsigned long *pgd = NULL, *p4d = NULL, *__pgd;
unsigned long asce_limit = mm->context.asce_limit;
/* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
VM_BUG_ON(asce_limit < _REGION2_SIZE);
if (end <= asce_limit)
return 0;
if (asce_limit == _REGION2_SIZE) {
p4d = crst_table_alloc(mm);
if (unlikely(!p4d))
goto err_p4d;
crst_table_init(p4d, _REGION2_ENTRY_EMPTY);
}
if (end > _REGION1_SIZE) {
pgd = crst_table_alloc(mm);
if (unlikely(!pgd))
goto err_pgd;
crst_table_init(pgd, _REGION1_ENTRY_EMPTY);
}
spin_lock_bh(&mm->page_table_lock);
/*
* This routine gets called with mmap_lock lock held and there is
* no reason to optimize for the case of otherwise. However, if
* that would ever change, the below check will let us know.
*/
VM_BUG_ON(asce_limit != mm->context.asce_limit);
if (p4d) {
__pgd = (unsigned long *) mm->pgd;
p4d_populate(mm, (p4d_t *) p4d, (pud_t *) __pgd);
mm->pgd = (pgd_t *) p4d;
mm->context.asce_limit = _REGION1_SIZE;
mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS | _ASCE_TYPE_REGION2;
mm_inc_nr_puds(mm);
}
if (pgd) {
__pgd = (unsigned long *) mm->pgd;
pgd_populate(mm, (pgd_t *) pgd, (p4d_t *) __pgd);
mm->pgd = (pgd_t *) pgd;
mm->context.asce_limit = TASK_SIZE_MAX;
mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
_ASCE_USER_BITS | _ASCE_TYPE_REGION1;
}
spin_unlock_bh(&mm->page_table_lock);
on_each_cpu(__crst_table_upgrade, mm, 0);
return 0;
err_pgd:
crst_table_free(mm, p4d);
err_p4d:
return -ENOMEM;
}
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;
}
#ifdef CONFIG_PGSTE
struct page *page_table_alloc_pgste(struct mm_struct *mm)
{
struct page *page;
u64 *table;
page = alloc_page(GFP_KERNEL);
if (page) {
table = (u64 *)page_to_virt(page);
memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
}
return page;
}
void page_table_free_pgste(struct page *page)
{
__free_page(page);
}
#endif /* CONFIG_PGSTE */
/*
* A 2KB-pgtable is either upper or lower half of a normal page.
* The second half of the page may be unused or used as another
* 2KB-pgtable.
*
* Whenever possible the parent page for a new 2KB-pgtable is picked
* from the list of partially allocated pages mm_context_t::pgtable_list.
* In case the list is empty a new parent page is allocated and added to
* the list.
*
* When a parent page gets fully allocated it contains 2KB-pgtables in both
* upper and lower halves and is removed from mm_context_t::pgtable_list.
*
* When 2KB-pgtable is freed from to fully allocated parent page that
* page turns partially allocated and added to mm_context_t::pgtable_list.
*
* If 2KB-pgtable is freed from the partially allocated parent page that
* page turns unused and gets removed from mm_context_t::pgtable_list.
* Furthermore, the unused parent page is released.
*
* As follows from the above, no unallocated or fully allocated parent
* pages are contained in mm_context_t::pgtable_list.
*
* The upper byte (bits 24-31) of the parent page _refcount is used
* for tracking contained 2KB-pgtables and has the following format:
*
* PP AA
* 01234567 upper byte (bits 24-31) of struct page::_refcount
* || ||
* || |+--- upper 2KB-pgtable is allocated
* || +---- lower 2KB-pgtable is allocated
* |+------- upper 2KB-pgtable is pending for removal
* +-------- lower 2KB-pgtable is pending for removal
*
* (See commit 620b4e903179 ("s390: use _refcount for pgtables") on why
* using _refcount is possible).
*
* When 2KB-pgtable is allocated the corresponding AA bit is set to 1.
* The parent page is either:
* - added to mm_context_t::pgtable_list in case the second half of the
* parent page is still unallocated;
* - removed from mm_context_t::pgtable_list in case both hales of the
* parent page are allocated;
* These operations are protected with mm_context_t::lock.
*
* When 2KB-pgtable is deallocated the corresponding AA bit is set to 0
* and the corresponding PP bit is set to 1 in a single atomic operation.
* Thus, PP and AA bits corresponding to the same 2KB-pgtable are mutually
* exclusive and may never be both set to 1!
* The parent page is either:
* - added to mm_context_t::pgtable_list in case the second half of the
* parent page is still allocated;
* - removed from mm_context_t::pgtable_list in case the second half of
* the parent page is unallocated;
* These operations are protected with mm_context_t::lock.
*
* It is important to understand that mm_context_t::lock only protects
* mm_context_t::pgtable_list and AA bits, but not the parent page itself
* and PP bits.
*
* Releasing the parent page happens whenever the PP bit turns from 1 to 0,
* while both AA bits and the second PP bit are already unset. Then the
* parent page does not contain any 2KB-pgtable fragment anymore, and it has
* also been removed from mm_context_t::pgtable_list. It is safe to release
* the page therefore.
*
* PGSTE memory spaces use full 4KB-pgtables and do not need most of the
* logic described above. Both AA bits are set to 1 to denote a 4KB-pgtable
* while the PP bits are never used, nor such a page is added to or removed
* from mm_context_t::pgtable_list.
*/
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.lock);
if (!list_empty(&mm->context.pgtable_list)) {
page = list_first_entry(&mm->context.pgtable_list,
struct page, lru);
mask = atomic_read(&page->_refcount) >> 24;
/*
* The pending removal bits must also be checked.
* Failure to do so might lead to an impossible
* value of (i.e 0x13 or 0x23) written to _refcount.
* Such values violate the assumption that pending and
* allocation bits are mutually exclusive, and the rest
* of the code unrails as result. That could lead to
* a whole bunch of races and corruptions.
*/
mask = (mask | (mask >> 4)) & 0x03U;
if (mask != 0x03U) {
table = (unsigned long *) page_to_virt(page);
bit = mask & 1; /* =1 -> second 2K */
if (bit)
table += PTRS_PER_PTE;
atomic_xor_bits(&page->_refcount,
0x01U << (bit + 24));
list_del(&page->lru);
}
}
spin_unlock_bh(&mm->context.lock);
if (table)
return table;
}
/* Allocate a fresh page */
page = alloc_page(GFP_KERNEL);
if (!page)
return NULL;
if (!pgtable_pte_page_ctor(page)) {
__free_page(page);
return NULL;
}
arch_set_page_dat(page, 0);
/* Initialize page table */
table = (unsigned long *) page_to_virt(page);
if (mm_alloc_pgste(mm)) {
/* Return 4K page table with PGSTEs */
atomic_xor_bits(&page->_refcount, 0x03U << 24);
memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
} else {
/* Return the first 2K fragment of the page */
atomic_xor_bits(&page->_refcount, 0x01U << 24);
memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
spin_lock_bh(&mm->context.lock);
list_add(&page->lru, &mm->context.pgtable_list);
spin_unlock_bh(&mm->context.lock);
}
return table;
}
static void page_table_release_check(struct page *page, void *table,
unsigned int half, unsigned int mask)
{
char msg[128];
if (!IS_ENABLED(CONFIG_DEBUG_VM) || !mask)
return;
snprintf(msg, sizeof(msg),
"Invalid pgtable %p release half 0x%02x mask 0x%02x",
table, half, mask);
dump_page(page, msg);
}
void page_table_free(struct mm_struct *mm, unsigned long *table)
{
unsigned int mask, bit, half;
struct page *page;
page = virt_to_page(table);
if (!mm_alloc_pgste(mm)) {
/* Free 2K page table fragment of a 4K page */
bit = ((unsigned long) table & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
spin_lock_bh(&mm->context.lock);
/*
* Mark the page for delayed release. The actual release
* will happen outside of the critical section from this
* function or from __tlb_remove_table()
*/
mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
mask >>= 24;
if (mask & 0x03U)
list_add(&page->lru, &mm->context.pgtable_list);
else
list_del(&page->lru);
spin_unlock_bh(&mm->context.lock);
mask = atomic_xor_bits(&page->_refcount, 0x10U << (bit + 24));
mask >>= 24;
if (mask != 0x00U)
return;
half = 0x01U << bit;
} else {
half = 0x03U;
mask = atomic_xor_bits(&page->_refcount, 0x03U << 24);
mask >>= 24;
}
page_table_release_check(page, table, half, mask);
pgtable_pte_page_dtor(page);
__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 = virt_to_page(table);
if (mm_alloc_pgste(mm)) {
gmap_unlink(mm, table, vmaddr);
table = (unsigned long *) ((unsigned long)table | 0x03U);
tlb_remove_table(tlb, table);
return;
}
bit = ((unsigned long) table & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
spin_lock_bh(&mm->context.lock);
/*
* Mark the page for delayed release. The actual release will happen
* outside of the critical section from __tlb_remove_table() or from
* page_table_free()
*/
mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
mask >>= 24;
if (mask & 0x03U)
list_add_tail(&page->lru, &mm->context.pgtable_list);
else
list_del(&page->lru);
spin_unlock_bh(&mm->context.lock);
table = (unsigned long *) ((unsigned long) table | (0x01U << bit));
tlb_remove_table(tlb, table);
}
void __tlb_remove_table(void *_table)
{
unsigned int mask = (unsigned long) _table & 0x03U, half = mask;
void *table = (void *)((unsigned long) _table ^ mask);
struct page *page = virt_to_page(table);
switch (half) {
case 0x00U: /* pmd, pud, or p4d */
free_pages((unsigned long)table, CRST_ALLOC_ORDER);
return;
case 0x01U: /* lower 2K of a 4K page table */
case 0x02U: /* higher 2K of a 4K page table */
mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
mask >>= 24;
if (mask != 0x00U)
return;
break;
case 0x03U: /* 4K page table with pgstes */
mask = atomic_xor_bits(&page->_refcount, 0x03U << 24);
mask >>= 24;
break;
}
page_table_release_check(page, table, half, mask);
pgtable_pte_page_dtor(page);
__free_page(page);
}
/*
* Base infrastructure required to generate basic asces, region, segment,
* and page tables that do not make use of enhanced features like EDAT1.
*/
static struct kmem_cache *base_pgt_cache;
static unsigned long *base_pgt_alloc(void)
{
unsigned long *table;
table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
if (table)
memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
return table;
}
static void base_pgt_free(unsigned long *table)
{
kmem_cache_free(base_pgt_cache, table);
}
static unsigned long *base_crst_alloc(unsigned long val)
{
unsigned long *table;
table = (unsigned long *)__get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
if (table)
crst_table_init(table, val);
return table;
}
static void base_crst_free(unsigned long *table)
{
free_pages((unsigned long)table, CRST_ALLOC_ORDER);
}
#define BASE_ADDR_END_FUNC(NAME, SIZE) \
static inline unsigned long base_##NAME##_addr_end(unsigned long addr, \
unsigned long end) \
{ \
unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1); \
\
return (next - 1) < (end - 1) ? next : end; \
}
BASE_ADDR_END_FUNC(page, _PAGE_SIZE)
BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
static inline unsigned long base_lra(unsigned long address)
{
unsigned long real;
asm volatile(
" lra %0,0(%1)\n"
: "=d" (real) : "a" (address) : "cc");
return real;
}
static int base_page_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
unsigned long *pte, next;
if (!alloc)
return 0;
pte = origin;
pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
do {
next = base_page_addr_end(addr, end);
*pte = base_lra(addr);
} while (pte++, addr = next, addr < end);
return 0;
}
static int base_segment_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
unsigned long *ste, next, *table;
int rc;
ste = origin;
ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
do {
next = base_segment_addr_end(addr, end);
if (*ste & _SEGMENT_ENTRY_INVALID) {
if (!alloc)
continue;
table = base_pgt_alloc();
if (!table)
return -ENOMEM;
*ste = __pa(table) | _SEGMENT_ENTRY;
}
table = __va(*ste & _SEGMENT_ENTRY_ORIGIN);
rc = base_page_walk(table, addr, next, alloc);
if (rc)
return rc;
if (!alloc)
base_pgt_free(table);
cond_resched();
} while (ste++, addr = next, addr < end);
return 0;
}
static int base_region3_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
unsigned long *rtte, next, *table;
int rc;
rtte = origin;
rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
do {
next = base_region3_addr_end(addr, end);
if (*rtte & _REGION_ENTRY_INVALID) {
if (!alloc)
continue;
table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
if (!table)
return -ENOMEM;
*rtte = __pa(table) | _REGION3_ENTRY;
}
table = __va(*rtte & _REGION_ENTRY_ORIGIN);
rc = base_segment_walk(table, addr, next, alloc);
if (rc)
return rc;
if (!alloc)
base_crst_free(table);
} while (rtte++, addr = next, addr < end);
return 0;
}
static int base_region2_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
unsigned long *rste, next, *table;
int rc;
rste = origin;
rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
do {
next = base_region2_addr_end(addr, end);
if (*rste & _REGION_ENTRY_INVALID) {
if (!alloc)
continue;
table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
if (!table)
return -ENOMEM;
*rste = __pa(table) | _REGION2_ENTRY;
}
table = __va(*rste & _REGION_ENTRY_ORIGIN);
rc = base_region3_walk(table, addr, next, alloc);
if (rc)
return rc;
if (!alloc)
base_crst_free(table);
} while (rste++, addr = next, addr < end);
return 0;
}
static int base_region1_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
unsigned long *rfte, next, *table;
int rc;
rfte = origin;
rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
do {
next = base_region1_addr_end(addr, end);
if (*rfte & _REGION_ENTRY_INVALID) {
if (!alloc)
continue;
table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
if (!table)
return -ENOMEM;
*rfte = __pa(table) | _REGION1_ENTRY;
}
table = __va(*rfte & _REGION_ENTRY_ORIGIN);
rc = base_region2_walk(table, addr, next, alloc);
if (rc)
return rc;
if (!alloc)
base_crst_free(table);
} while (rfte++, addr = next, addr < end);
return 0;
}
/**
* base_asce_free - free asce and tables returned from base_asce_alloc()
* @asce: asce to be freed
*
* Frees all region, segment, and page tables that were allocated with a
* corresponding base_asce_alloc() call.
*/
void base_asce_free(unsigned long asce)
{
unsigned long *table = __va(asce & _ASCE_ORIGIN);
if (!asce)
return;
switch (asce & _ASCE_TYPE_MASK) {
case _ASCE_TYPE_SEGMENT:
base_segment_walk(table, 0, _REGION3_SIZE, 0);
break;
case _ASCE_TYPE_REGION3:
base_region3_walk(table, 0, _REGION2_SIZE, 0);
break;
case _ASCE_TYPE_REGION2:
base_region2_walk(table, 0, _REGION1_SIZE, 0);
break;
case _ASCE_TYPE_REGION1:
base_region1_walk(table, 0, TASK_SIZE_MAX, 0);
break;
}
base_crst_free(table);
}
static int base_pgt_cache_init(void)
{
static DEFINE_MUTEX(base_pgt_cache_mutex);
unsigned long sz = _PAGE_TABLE_SIZE;
if (base_pgt_cache)
return 0;
mutex_lock(&base_pgt_cache_mutex);
if (!base_pgt_cache)
base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
mutex_unlock(&base_pgt_cache_mutex);
return base_pgt_cache ? 0 : -ENOMEM;
}
/**
* base_asce_alloc - create kernel mapping without enhanced DAT features
* @addr: virtual start address of kernel mapping
* @num_pages: number of consecutive pages
*
* Generate an asce, including all required region, segment and page tables,
* that can be used to access the virtual kernel mapping. The difference is
* that the returned asce does not make use of any enhanced DAT features like
* e.g. large pages. This is required for some I/O functions that pass an
* asce, like e.g. some service call requests.
*
* Note: the returned asce may NEVER be attached to any cpu. It may only be
* used for I/O requests. tlb entries that might result because the
* asce was attached to a cpu won't be cleared.
*/
unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
{
unsigned long asce, *table, end;
int rc;
if (base_pgt_cache_init())
return 0;
end = addr + num_pages * PAGE_SIZE;
if (end <= _REGION3_SIZE) {
table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
if (!table)
return 0;
rc = base_segment_walk(table, addr, end, 1);
asce = __pa(table) | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
} else if (end <= _REGION2_SIZE) {
table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
if (!table)
return 0;
rc = base_region3_walk(table, addr, end, 1);
asce = __pa(table) | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
} else if (end <= _REGION1_SIZE) {
table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
if (!table)
return 0;
rc = base_region2_walk(table, addr, end, 1);
asce = __pa(table) | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
} else {
table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
if (!table)
return 0;
rc = base_region1_walk(table, addr, end, 1);
asce = __pa(table) | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
}
if (rc) {
base_asce_free(asce);
asce = 0;
}
return asce;
}