// SPDX-License-Identifier: GPL-2.0
/*
* Device Memory Migration functionality.
*
* Originally written by Jérôme Glisse.
*/
#include <linux/export.h>
#include <linux/memremap.h>
#include <linux/migrate.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/mmu_notifier.h>
#include <linux/oom.h>
#include <linux/pagewalk.h>
#include <linux/rmap.h>
#include <linux/leafops.h>
#include <linux/pgalloc.h>
#include <asm/tlbflush.h>
#include "internal.h"
static int migrate_vma_collect_skip(unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
unsigned long addr;
for (addr = start; addr < end; addr += PAGE_SIZE) {
migrate->dst[migrate->npages] = 0;
migrate->src[migrate->npages++] = 0;
}
return 0;
}
static int migrate_vma_collect_hole(unsigned long start,
unsigned long end,
__always_unused int depth,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
unsigned long addr;
/* Only allow populating anonymous memory. */
if (!vma_is_anonymous(walk->vma))
return migrate_vma_collect_skip(start, end, walk);
if (thp_migration_supported() &&
(migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) &&
(IS_ALIGNED(start, HPAGE_PMD_SIZE) &&
IS_ALIGNED(end, HPAGE_PMD_SIZE))) {
migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE |
MIGRATE_PFN_COMPOUND;
migrate->dst[migrate->npages] = 0;
migrate->npages++;
migrate->cpages++;
/*
* Collect the remaining entries as holes, in case we
* need to split later
*/
return migrate_vma_collect_skip(start + PAGE_SIZE, end, walk);
}
for (addr = start; addr < end; addr += PAGE_SIZE) {
migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
migrate->dst[migrate->npages] = 0;
migrate->npages++;
migrate->cpages++;
}
return 0;
}
/**
* migrate_vma_split_folio() - Helper function to split a THP folio
* @folio: the folio to split
* @fault_page: struct page associated with the fault if any
*
* If @folio is not the folio containing @fault_page, the caller must hold a
* reference on @folio. The helper consumes that reference.
*
* Returns 0 on success
*/
static int migrate_vma_split_folio(struct folio *folio,
struct page *fault_page)
{
int ret;
struct folio *fault_folio = fault_page ? page_folio(fault_page) : NULL;
struct folio *new_fault_folio = NULL;
if (folio != fault_folio)
folio_lock(folio);
ret = split_folio(folio);
if (ret) {
if (folio != fault_folio) {
folio_unlock(folio);
folio_put(folio);
}
return ret;
}
new_fault_folio = fault_page ? page_folio(fault_page) : NULL;
/*
* Ensure the lock is held on the correct
* folio after the split
*/
if (!new_fault_folio) {
folio_unlock(folio);
folio_put(folio);
} else if (folio != new_fault_folio) {
if (new_fault_folio != fault_folio) {
folio_get(new_fault_folio);
folio_lock(new_fault_folio);
}
folio_unlock(folio);
folio_put(folio);
}
return 0;
}
/** migrate_vma_collect_huge_pmd - collect THP pages without splitting the
* folio for device private pages.
* @pmdp: pointer to pmd entry
* @start: start address of the range for migration
* @end: end address of the range for migration
* @walk: mm_walk callback structure
* @fault_folio: folio associated with the fault if any
*
* Collect the huge pmd entry at @pmdp for migration and set the
* MIGRATE_PFN_COMPOUND flag in the migrate src entry to indicate that
* migration will occur at HPAGE_PMD granularity
*/
static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start,
unsigned long end, struct mm_walk *walk,
struct folio *fault_folio)
{
struct mm_struct *mm = walk->mm;
struct folio *folio;
struct migrate_vma *migrate = walk->private;
spinlock_t *ptl;
int ret;
unsigned long write = 0;
ptl = pmd_lock(mm, pmdp);
if (pmd_none(*pmdp)) {
spin_unlock(ptl);
return migrate_vma_collect_hole(start, end, -1, walk);
}
if (pmd_trans_huge(*pmdp)) {
if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) {
spin_unlock(ptl);
return migrate_vma_collect_skip(start, end, walk);
}
folio = pmd_folio(*pmdp);
if (is_huge_zero_folio(folio)) {
spin_unlock(ptl);
return migrate_vma_collect_hole(start, end, -1, walk);
}
if (pmd_write(*pmdp))
write = MIGRATE_PFN_WRITE;
} else if (!pmd_present(*pmdp)) {
const softleaf_t entry = softleaf_from_pmd(*pmdp);
if (!softleaf_is_device_private(entry) ||
!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_PRIVATE)) {
spin_unlock(ptl);
return migrate_vma_collect_skip(start, end, walk);
}
folio = softleaf_to_folio(entry);
if (folio->pgmap->owner != migrate->pgmap_owner) {
spin_unlock(ptl);
return migrate_vma_collect_skip(start, end, walk);
}
if (softleaf_is_device_private_write(entry))
write = MIGRATE_PFN_WRITE;
} else {
spin_unlock(ptl);
return -EAGAIN;
}
folio_get(folio);
if (folio != fault_folio && unlikely(!folio_trylock(folio))) {
spin_unlock(ptl);
folio_put(folio);
return migrate_vma_collect_skip(start, end, walk);
}
if (thp_migration_supported() &&
(migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) &&
(IS_ALIGNED(start, HPAGE_PMD_SIZE) &&
IS_ALIGNED(end, HPAGE_PMD_SIZE))) {
struct page_vma_mapped_walk pvmw = {
.ptl = ptl,
.address = start,
.pmd = pmdp,
.vma = walk->vma,
};
unsigned long pfn = page_to_pfn(folio_page(folio, 0));
migrate->src[migrate->npages] = migrate_pfn(pfn) | write
| MIGRATE_PFN_MIGRATE
| MIGRATE_PFN_COMPOUND;
migrate->dst[migrate->npages++] = 0;
migrate->cpages++;
ret = set_pmd_migration_entry(&pvmw, folio_page(folio, 0));
if (ret) {
migrate->npages--;
migrate->cpages--;
migrate->src[migrate->npages] = 0;
migrate->dst[migrate->npages] = 0;
goto fallback;
}
migrate_vma_collect_skip(start + PAGE_SIZE, end, walk);
spin_unlock(ptl);
return 0;
}
fallback:
spin_unlock(ptl);
if (!folio_test_large(folio))
goto done;
ret = split_folio(folio);
if (fault_folio != folio)
folio_unlock(folio);
folio_put(folio);
if (ret)
return migrate_vma_collect_skip(start, end, walk);
if (pmd_none(pmdp_get_lockless(pmdp)))
return migrate_vma_collect_hole(start, end, -1, walk);
done:
return -ENOENT;
}
static int migrate_vma_collect_pmd(pmd_t *pmdp,
unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct migrate_vma *migrate = walk->private;
struct vm_area_struct *vma = walk->vma;
struct mm_struct *mm = vma->vm_mm;
unsigned long addr = start, unmapped = 0;
spinlock_t *ptl;
struct folio *fault_folio = migrate->fault_page ?
page_folio(migrate->fault_page) : NULL;
pte_t *ptep;
again:
if (pmd_trans_huge(*pmdp) || !pmd_present(*pmdp)) {
int ret = migrate_vma_collect_huge_pmd(pmdp, start, end, walk, fault_folio);
if (ret == -EAGAIN)
goto again;
if (ret == 0)
return 0;
}
ptep = pte_offset_map_lock(mm, pmdp, start, &ptl);
if (!ptep)
goto again;
lazy_mmu_mode_enable();
ptep += (addr - start) / PAGE_SIZE;
for (; addr < end; addr += PAGE_SIZE, ptep++) {
struct dev_pagemap *pgmap;
unsigned long mpfn = 0, pfn;
struct folio *folio;
struct page *page;
softleaf_t entry;
pte_t pte;
pte = ptep_get(ptep);
if (pte_none(pte)) {
if (vma_is_anonymous(vma)) {
mpfn = MIGRATE_PFN_MIGRATE;
migrate->cpages++;
}
goto next;
}
if (!pte_present(pte)) {
/*
* Only care about unaddressable device page special
* page table entry. Other special swap entries are not
* migratable, and we ignore regular swapped page.
*/
entry = softleaf_from_pte(pte);
if (!softleaf_is_device_private(entry))
goto next;
page = softleaf_to_page(entry);
pgmap = page_pgmap(page);
if (!(migrate->flags &
MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
pgmap->owner != migrate->pgmap_owner)
goto next;
folio = page_folio(page);
if (folio_test_large(folio)) {
int ret;
/* migrate_vma_split_folio() consumes this reference */
if (folio != fault_folio)
folio_get(folio);
lazy_mmu_mode_disable();
pte_unmap_unlock(ptep, ptl);
ret = migrate_vma_split_folio(folio,
migrate->fault_page);
if (ret) {
if (unmapped)
flush_tlb_range(walk->vma, start, end);
return migrate_vma_collect_skip(addr, end, walk);
}
goto again;
}
mpfn = migrate_pfn(page_to_pfn(page)) |
MIGRATE_PFN_MIGRATE;
if (softleaf_is_device_private_write(entry))
mpfn |= MIGRATE_PFN_WRITE;
} else {
pfn = pte_pfn(pte);
if (is_zero_pfn(pfn) &&
(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) {
mpfn = MIGRATE_PFN_MIGRATE;
migrate->cpages++;
goto next;
}
page = vm_normal_page(migrate->vma, addr, pte);
if (page && !is_zone_device_page(page) &&
!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) {
goto next;
} else if (page && is_device_coherent_page(page)) {
pgmap = page_pgmap(page);
if (!(migrate->flags &
MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
pgmap->owner != migrate->pgmap_owner)
goto next;
}
folio = page ? page_folio(page) : NULL;
if (folio && folio_test_large(folio)) {
int ret;
/* migrate_vma_split_folio() consumes this reference */
if (folio != fault_folio)
folio_get(folio);
lazy_mmu_mode_disable();
pte_unmap_unlock(ptep, ptl);
ret = migrate_vma_split_folio(folio,
migrate->fault_page);
if (ret) {
if (unmapped)
flush_tlb_range(walk->vma, start, end);
return migrate_vma_collect_skip(addr, end, walk);
}
goto again;
}
mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
}
if (!page || !page->mapping) {
mpfn = 0;
goto next;
}
/*
* By getting a reference on the folio we pin it and that blocks
* any kind of migration. Side effect is that it "freezes" the
* pte.
*
* We drop this reference after isolating the folio from the lru
* for non device folio (device folio are not on the lru and thus
* can't be dropped from it).
*/
folio = page_folio(page);
folio_get(folio);
/*
* We rely on folio_trylock() to avoid deadlock between
* concurrent migrations where each is waiting on the others
* folio lock. If we can't immediately lock the folio we fail this
* migration as it is only best effort anyway.
*
* If we can lock the folio it's safe to set up a migration entry
* now. In the common case where the folio is mapped once in a
* single process setting up the migration entry now is an
* optimisation to avoid walking the rmap later with
* try_to_migrate().
*/
if (fault_folio == folio || folio_trylock(folio)) {
bool anon_exclusive;
pte_t swp_pte;
if (pte_present(pte))
flush_cache_page(vma, addr, pte_pfn(pte));
anon_exclusive = folio_test_anon(folio) &&
PageAnonExclusive(page);
if (anon_exclusive) {
pte = ptep_clear_flush(vma, addr, ptep);
if (folio_try_share_anon_rmap_pte(folio, page)) {
set_pte_at(mm, addr, ptep, pte);
if (fault_folio != folio)
folio_unlock(folio);
folio_put(folio);
mpfn = 0;
goto next;
}
} else {
pte = ptep_get_and_clear(mm, addr, ptep);
}
migrate->cpages++;
/* Set the dirty flag on the folio now the pte is gone. */
if (pte_present(pte) && pte_dirty(pte))
folio_mark_dirty(folio);
/* Setup special migration page table entry */
if (mpfn & MIGRATE_PFN_WRITE)
entry = make_writable_migration_entry(
page_to_pfn(page));
else if (anon_exclusive)
entry = make_readable_exclusive_migration_entry(
page_to_pfn(page));
else
entry = make_readable_migration_entry(
page_to_pfn(page));
if (pte_present(pte)) {
if (pte_young(pte))
entry = make_migration_entry_young(entry);
if (pte_dirty(pte))
entry = make_migration_entry_dirty(entry);
}
swp_pte = swp_entry_to_pte(entry);
if (pte_present(pte)) {
if (pte_soft_dirty(pte))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
if (pte_uffd(pte))
swp_pte = pte_swp_mkuffd(swp_pte);
} else {
if (pte_swp_soft_dirty(pte))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
if (pte_swp_uffd(pte))
swp_pte = pte_swp_mkuffd(swp_pte);
}
set_pte_at(mm, addr, ptep, swp_pte);
/*
* This is like regular unmap: we remove the rmap and
* drop the folio refcount. The folio won't be freed, as
* we took a reference just above.
*/
folio_remove_rmap_pte(folio, page, vma);
folio_put(folio);
if (pte_present(pte))
unmapped++;
} else {
folio_put(folio);
mpfn = 0;
}
next:
migrate->dst[migrate->npages] = 0;
migrate->src[migrate->npages++] = mpfn;
}
/* Only flush the TLB if we actually modified any entries */
if (unmapped)
flush_tlb_range(walk->vma, start, end);
lazy_mmu_mode_disable();
pte_unmap_unlock(ptep - 1, ptl);
return 0;
}
static const struct mm_walk_ops migrate_vma_walk_ops = {
.pmd_entry = migrate_vma_collect_pmd,
.pte_hole = migrate_vma_collect_hole,
.walk_lock = PGWALK_RDLOCK,
};
/*
* migrate_vma_collect() - collect pages over a range of virtual addresses
* @migrate: migrate struct containing all migration information
*
* This will walk the CPU page table. For each virtual address backed by a
* valid page, it updates the src array and takes a reference on the page, in
* order to pin the page until we lock it and unmap it.
*/
static void migrate_vma_collect(struct migrate_vma *migrate)
{
struct mmu_notifier_range range;
/*
* Note that the pgmap_owner is passed to the mmu notifier callback so
* that the registered device driver can skip invalidating device
* private page mappings that won't be migrated.
*/
mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
migrate->vma->vm_mm, migrate->start, migrate->end,
migrate->pgmap_owner);
mmu_notifier_invalidate_range_start(&range);
walk_page_range_vma(migrate->vma, migrate->start, migrate->end,
&migrate_vma_walk_ops, migrate);
mmu_notifier_invalidate_range_end(&range);
migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
}
/*
* migrate_vma_check_page() - check if page is pinned or not
* @page: struct page to check
*
* Pinned pages cannot be migrated. This is the same test as in
* folio_migrate_mapping(), except that here we allow migration of a
* ZONE_DEVICE page.
*/
static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
{
struct folio *folio = page_folio(page);
/*
* One extra ref because caller holds an extra reference, either from
* folio_isolate_lru() for a regular folio, or migrate_vma_collect() for
* a device folio.
*/
int extra = 1 + (page == fault_page);
/* Page from ZONE_DEVICE have one extra reference */
if (folio_is_zone_device(folio))
extra++;
/* For file back page */
if (folio_mapping(folio))
extra += 1 + folio_has_private(folio);
if ((folio_ref_count(folio) - extra) > folio_mapcount(folio))
return false;
return true;
}
/*
* Unmaps pages for migration. Returns number of source pfns marked as
* migrating.
*/
static unsigned long migrate_device_unmap(unsigned long *src_pfns,
unsigned long npages,
struct page *fault_page)
{
struct folio *fault_folio = fault_page ?
page_folio(fault_page) : NULL;
unsigned long i, restore = 0;
bool allow_drain = true;
unsigned long unmapped = 0;
lru_add_drain();
for (i = 0; i < npages; ) {
struct page *page = migrate_pfn_to_page(src_pfns[i]);
struct folio *folio;
unsigned int nr = 1;
if (!page) {
if (src_pfns[i] & MIGRATE_PFN_MIGRATE)
unmapped++;
goto next;
}
folio = page_folio(page);
nr = folio_nr_pages(folio);
if (nr > 1)
src_pfns[i] |= MIGRATE_PFN_COMPOUND;
/* ZONE_DEVICE folios are not on LRU */
if (!folio_is_zone_device(folio)) {
if (!folio_test_lru(folio) && allow_drain) {
/* Drain CPU's lru cache */
lru_add_drain_all();
allow_drain = false;
}
if (!folio_isolate_lru(folio)) {
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
restore++;
goto next;
}
/* Drop the reference we took in collect */
folio_put(folio);
}
if (folio_mapped(folio))
try_to_migrate(folio, 0);
if (folio_mapped(folio) ||
!migrate_vma_check_page(page, fault_page)) {
if (!folio_is_zone_device(folio)) {
folio_get(folio);
folio_putback_lru(folio);
}
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
restore++;
goto next;
}
unmapped++;
next:
i += nr;
}
for (i = 0; i < npages && restore; i++) {
struct page *page = migrate_pfn_to_page(src_pfns[i]);
struct folio *folio;
if (!page || (src_pfns[i] & MIGRATE_PFN_MIGRATE))
continue;
folio = page_folio(page);
remove_migration_ptes(folio, folio, 0);
src_pfns[i] = 0;
if (fault_folio != folio)
folio_unlock(folio);
folio_put(folio);
restore--;
}
return unmapped;
}
/*
* migrate_vma_unmap() - replace page mapping with special migration pte entry
* @migrate: migrate struct containing all migration information
*
* Isolate pages from the LRU and replace mappings (CPU page table pte) with a
* special migration pte entry and check if it has been pinned. Pinned pages are
* restored because we cannot migrate them.
*
* This is the last step before we call the device driver callback to allocate
* destination memory and copy contents of original page over to new page.
*/
static void migrate_vma_unmap(struct migrate_vma *migrate)
{
migrate->cpages = migrate_device_unmap(migrate->src, migrate->npages,
migrate->fault_page);
}
/**
* migrate_vma_setup() - prepare to migrate a range of memory
* @args: contains the vma, start, and pfns arrays for the migration
*
* Returns: negative errno on failures, 0 when 0 or more pages were migrated
* without an error.
*
* Prepare to migrate a range of memory virtual address range by collecting all
* the pages backing each virtual address in the range, saving them inside the
* src array. Then lock those pages and unmap them. Once the pages are locked
* and unmapped, check whether each page is pinned or not. Pages that aren't
* pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
* corresponding src array entry. Then restores any pages that are pinned, by
* remapping and unlocking those pages.
*
* The caller should then allocate destination memory and copy source memory to
* it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
* flag set). Once these are allocated and copied, the caller must update each
* corresponding entry in the dst array with the pfn value of the destination
* page and with MIGRATE_PFN_VALID. Destination pages must be locked via
* lock_page().
*
* Note that the caller does not have to migrate all the pages that are marked
* with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
* device memory to system memory. If the caller cannot migrate a device page
* back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
* consequences for the userspace process, so it must be avoided if at all
* possible.
*
* For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
* do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
* allowing the caller to allocate device memory for those unbacked virtual
* addresses. For this the caller simply has to allocate device memory and
* properly set the destination entry like for regular migration. Note that
* this can still fail, and thus inside the device driver you must check if the
* migration was successful for those entries after calling migrate_vma_pages(),
* just like for regular migration.
*
* After that, the callers must call migrate_vma_pages() to go over each entry
* in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
* set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
* then migrate_vma_pages() to migrate struct page information from the source
* struct page to the destination struct page. If it fails to migrate the
* struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
* src array.
*
* At this point all successfully migrated pages have an entry in the src
* array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
* array entry with MIGRATE_PFN_VALID flag set.
*
* Once migrate_vma_pages() returns the caller may inspect which pages were
* successfully migrated, and which were not. Successfully migrated pages will
* have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
*
* It is safe to update device page table after migrate_vma_pages() because
* both destination and source page are still locked, and the mmap_lock is held
* in read mode (hence no one can unmap the range being migrated).
*
* Once the caller is done cleaning up things and updating its page table (if it
* chose to do so, this is not an obligation) it finally calls
* migrate_vma_finalize() to update the CPU page table to point to new pages
* for successfully migrated pages or otherwise restore the CPU page table to
* point to the original source pages.
*/
int migrate_vma_setup(struct migrate_vma *args)
{
long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
args->start &= PAGE_MASK;
args->end &= PAGE_MASK;
if (!args->vma || is_vm_hugetlb_page(args->vma) ||
(args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
return -EINVAL;
if (nr_pages <= 0)
return -EINVAL;
if (args->start < args->vma->vm_start ||
args->start >= args->vma->vm_end)
return -EINVAL;
if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
return -EINVAL;
if (!args->src || !args->dst)
return -EINVAL;
if (args->fault_page && !is_device_private_page(args->fault_page))
return -EINVAL;
if (args->fault_page && !PageLocked(args->fault_page))
return -EINVAL;
memset(args->src, 0, sizeof(*args->src) * nr_pages);
args->cpages = 0;
args->npages = 0;
migrate_vma_collect(args);
if (args->cpages)
migrate_vma_unmap(args);
/*
* At this point pages are locked and unmapped, and thus they have
* stable content and can safely be copied to destination memory that
* is allocated by the drivers.
*/
return 0;
}
EXPORT_SYMBOL(migrate_vma_setup);
#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
/**
* migrate_vma_insert_huge_pmd_page: Insert a huge folio into @migrate->vma->vm_mm
* at @addr. folio is already allocated as a part of the migration process with
* large page.
*
* @page needs to be initialized and setup after it's allocated. The code bits
* here follow closely the code in __do_huge_pmd_anonymous_page(). This API does
* not support THP zero pages.
*
* @migrate: migrate_vma arguments
* @addr: address where the folio will be inserted
* @page: page to be inserted at @addr
* @src: src pfn which is being migrated
* @pmdp: pointer to the pmd
*/
static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate,
unsigned long addr,
struct page *page,
unsigned long *src,
pmd_t *pmdp)
{
struct vm_area_struct *vma = migrate->vma;
gfp_t gfp = vma_thp_gfp_mask(vma);
struct folio *folio = page_folio(page);
int ret;
vm_fault_t csa_ret;
spinlock_t *ptl;
pgtable_t pgtable;
pmd_t entry;
bool flush = false;
unsigned long i;
VM_WARN_ON_ONCE(!folio);
if (!thp_vma_suitable_order(vma, addr, HPAGE_PMD_ORDER))
return -EINVAL;
ret = anon_vma_prepare(vma);
if (ret)
return ret;
folio_set_order(folio, HPAGE_PMD_ORDER);
folio_set_large_rmappable(folio);
if (mem_cgroup_charge(folio, migrate->vma->vm_mm, gfp)) {
count_vm_event(THP_FAULT_FALLBACK);
count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
ret = -ENOMEM;
goto abort;
}
__folio_mark_uptodate(folio);
pgtable = pte_alloc_one(vma->vm_mm);
if (unlikely(!pgtable))
goto abort;
if (folio_is_device_private(folio)) {
swp_entry_t swp_entry;
if (vma->vm_flags & VM_WRITE)
swp_entry = make_writable_device_private_entry(
page_to_pfn(page));
else
swp_entry = make_readable_device_private_entry(
page_to_pfn(page));
entry = softleaf_to_pmd(swp_entry);
} else {
if (folio_is_zone_device(folio) &&
!folio_is_device_coherent(folio)) {
goto free_abort;
}
entry = folio_mk_pmd(folio, vma->vm_page_prot);
if (vma->vm_flags & VM_WRITE)
entry = pmd_mkwrite(pmd_mkdirty(entry), vma);
}
ptl = pmd_lock(vma->vm_mm, pmdp);
csa_ret = check_stable_address_space(vma->vm_mm);
if (csa_ret)
goto unlock_abort;
/*
* Check for userfaultfd but do not deliver the fault. Instead,
* just back off.
*/
if (userfaultfd_missing(vma))
goto unlock_abort;
if (is_huge_zero_pmd(*pmdp))
flush = true;
else if (!pmd_none(*pmdp))
goto unlock_abort;
add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
if (!folio_is_zone_device(folio))
folio_add_lru_vma(folio, vma);
folio_get(folio);
if (flush) {
pte_free(vma->vm_mm, pgtable);
flush_cache_page(vma, addr, addr + HPAGE_PMD_SIZE);
pmdp_invalidate(vma, addr, pmdp);
} else {
pgtable_trans_huge_deposit(vma->vm_mm, pmdp, pgtable);
mm_inc_nr_ptes(vma->vm_mm);
}
set_pmd_at(vma->vm_mm, addr, pmdp, entry);
update_mmu_cache_pmd(vma, addr, pmdp);
spin_unlock(ptl);
count_vm_event(THP_FAULT_ALLOC);
count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_ALLOC);
count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
return 0;
unlock_abort:
spin_unlock(ptl);
free_abort:
pte_free(vma->vm_mm, pgtable);
abort:
for (i = 0; i < HPAGE_PMD_NR; i++)
src[i] &= ~MIGRATE_PFN_MIGRATE;
return 0;
}
static int migrate_vma_split_unmapped_folio(struct migrate_vma *migrate,
unsigned long idx, unsigned long addr,
struct folio *folio)
{
unsigned long i;
unsigned long pfn;
unsigned long flags;
int ret = 0;
/*
* take a reference, since split_huge_pmd_address() with freeze = true
* drops a reference at the end.
*/
folio_get(folio);
split_huge_pmd_address(migrate->vma, addr, true);
ret = folio_split_unmapped(folio, 0);
if (ret)
return ret;
migrate->src[idx] &= ~MIGRATE_PFN_COMPOUND;
flags = migrate->src[idx] & ((1UL << MIGRATE_PFN_SHIFT) - 1);
pfn = migrate->src[idx] >> MIGRATE_PFN_SHIFT;
for (i = 1; i < HPAGE_PMD_NR; i++)
migrate->src[i+idx] = migrate_pfn(pfn + i) | flags;
return ret;
}
#else /* !CONFIG_ARCH_HAS_PMD_SOFTLEAVES */
static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate,
unsigned long addr,
struct page *page,
unsigned long *src,
pmd_t *pmdp)
{
return 0;
}
static int migrate_vma_split_unmapped_folio(struct migrate_vma *migrate,
unsigned long idx, unsigned long addr,
struct folio *folio)
{
return 0;
}
#endif
static unsigned long migrate_vma_nr_pages(unsigned long *src)
{
unsigned long nr = 1;
#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
if (*src & MIGRATE_PFN_COMPOUND)
nr = HPAGE_PMD_NR;
#else
if (*src & MIGRATE_PFN_COMPOUND)
VM_WARN_ON_ONCE(true);
#endif
return nr;
}
/*
* This code closely matches the code in:
* __handle_mm_fault()
* handle_pte_fault()
* do_anonymous_page()
* to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
* private or coherent page.
*/
static void migrate_vma_insert_page(struct migrate_vma *migrate,
unsigned long addr,
unsigned long *dst,
unsigned long *src)
{
struct page *page = migrate_pfn_to_page(*dst);
struct folio *folio = page_folio(page);
struct vm_area_struct *vma = migrate->vma;
struct mm_struct *mm = vma->vm_mm;
bool flush = false;
spinlock_t *ptl;
pte_t entry;
pgd_t *pgdp;
p4d_t *p4dp;
pud_t *pudp;
pmd_t *pmdp;
pte_t *ptep;
pte_t orig_pte;
/* Only allow populating anonymous memory */
if (!vma_is_anonymous(vma))
goto abort;
pgdp = pgd_offset(mm, addr);
p4dp = p4d_alloc(mm, pgdp, addr);
if (!p4dp)
goto abort;
pudp = pud_alloc(mm, p4dp, addr);
if (!pudp)
goto abort;
pmdp = pmd_alloc(mm, pudp, addr);
if (!pmdp)
goto abort;
if (thp_migration_supported() && (*dst & MIGRATE_PFN_COMPOUND)) {
int ret = migrate_vma_insert_huge_pmd_page(migrate, addr, page,
src, pmdp);
if (ret)
goto abort;
return;
}
if (!pmd_none(*pmdp)) {
if (pmd_trans_huge(*pmdp)) {
if (!is_huge_zero_pmd(*pmdp))
goto abort;
split_huge_pmd(vma, pmdp, addr);
} else if (pmd_leaf(*pmdp))
goto abort;
}
if (pte_alloc(mm, pmdp))
goto abort;
if (unlikely(anon_vma_prepare(vma)))
goto abort;
if (mem_cgroup_charge(folio, vma->vm_mm, GFP_KERNEL))
goto abort;
/*
* The memory barrier inside __folio_mark_uptodate makes sure that
* preceding stores to the folio contents become visible before
* the set_pte_at() write.
*/
__folio_mark_uptodate(folio);
if (folio_is_device_private(folio)) {
swp_entry_t swp_entry;
if (vma->vm_flags & VM_WRITE)
swp_entry = make_writable_device_private_entry(
page_to_pfn(page));
else
swp_entry = make_readable_device_private_entry(
page_to_pfn(page));
entry = swp_entry_to_pte(swp_entry);
} else {
if (folio_is_zone_device(folio) &&
!folio_is_device_coherent(folio)) {
pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
goto abort;
}
entry = mk_pte(page, vma->vm_page_prot);
if (vma->vm_flags & VM_WRITE)
entry = pte_mkwrite(pte_mkdirty(entry), vma);
}
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
if (!ptep)
goto abort;
orig_pte = ptep_get(ptep);
if (check_stable_address_space(mm))
goto unlock_abort;
if (pte_present(orig_pte)) {
unsigned long pfn = pte_pfn(orig_pte);
if (!is_zero_pfn(pfn))
goto unlock_abort;
flush = true;
} else if (!pte_none(orig_pte))
goto unlock_abort;
/*
* Check for userfaultfd but do not deliver the fault. Instead,
* just back off.
*/
if (userfaultfd_missing(vma))
goto unlock_abort;
inc_mm_counter(mm, MM_ANONPAGES);
folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
if (!folio_is_zone_device(folio))
folio_add_lru_vma(folio, vma);
folio_get(folio);
if (flush) {
flush_cache_page(vma, addr, pte_pfn(orig_pte));
ptep_clear_flush(vma, addr, ptep);
}
set_pte_at(mm, addr, ptep, entry);
update_mmu_cache(vma, addr, ptep);
pte_unmap_unlock(ptep, ptl);
*src = MIGRATE_PFN_MIGRATE;
return;
unlock_abort:
pte_unmap_unlock(ptep, ptl);
abort:
*src &= ~MIGRATE_PFN_MIGRATE;
}
static void __migrate_device_pages(unsigned long *src_pfns,
unsigned long *dst_pfns, unsigned long npages,
struct migrate_vma *migrate)
{
struct mmu_notifier_range range;
unsigned long i, j;
bool notified = false;
unsigned long addr;
for (i = 0; i < npages; ) {
struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
struct page *page = migrate_pfn_to_page(src_pfns[i]);
struct address_space *mapping;
struct folio *newfolio, *folio;
int r, extra_cnt = 0;
unsigned long nr = 1;
if (!newpage) {
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
goto next;
}
if (!page) {
unsigned long addr;
if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE))
goto next;
/*
* The only time there is no vma is when called from
* migrate_device_coherent_folio(). However this isn't
* called if the page could not be unmapped.
*/
VM_BUG_ON(!migrate);
addr = migrate->start + i*PAGE_SIZE;
if (!notified) {
notified = true;
mmu_notifier_range_init_owner(&range,
MMU_NOTIFY_MIGRATE, 0,
migrate->vma->vm_mm, addr, migrate->end,
migrate->pgmap_owner);
mmu_notifier_invalidate_range_start(&range);
}
if ((src_pfns[i] & MIGRATE_PFN_COMPOUND) &&
(!(dst_pfns[i] & MIGRATE_PFN_COMPOUND))) {
nr = migrate_vma_nr_pages(&src_pfns[i]);
src_pfns[i] &= ~MIGRATE_PFN_COMPOUND;
} else {
nr = 1;
}
for (j = 0; j < nr && i + j < npages; j++) {
src_pfns[i+j] |= MIGRATE_PFN_MIGRATE;
migrate_vma_insert_page(migrate,
addr + j * PAGE_SIZE,
&dst_pfns[i+j], &src_pfns[i+j]);
}
goto next;
}
newfolio = page_folio(newpage);
folio = page_folio(page);
mapping = folio_mapping(folio);
/*
* If THP migration is enabled, check if both src and dst
* can migrate large pages
*/
if (thp_migration_supported()) {
if ((src_pfns[i] & MIGRATE_PFN_MIGRATE) &&
(src_pfns[i] & MIGRATE_PFN_COMPOUND) &&
!(dst_pfns[i] & MIGRATE_PFN_COMPOUND)) {
if (!migrate) {
src_pfns[i] &= ~(MIGRATE_PFN_MIGRATE |
MIGRATE_PFN_COMPOUND);
goto next;
}
nr = 1 << folio_order(folio);
addr = migrate->start + i * PAGE_SIZE;
if (migrate_vma_split_unmapped_folio(migrate, i, addr, folio)) {
src_pfns[i] &= ~(MIGRATE_PFN_MIGRATE |
MIGRATE_PFN_COMPOUND);
goto next;
}
/*
* reset nr so that only first after-split folio
* is processed below
*/
VM_WARN_ON_ONCE(folio_test_large(folio));
nr = 1;
} else if ((src_pfns[i] & MIGRATE_PFN_MIGRATE) &&
(dst_pfns[i] & MIGRATE_PFN_COMPOUND) &&
!(src_pfns[i] & MIGRATE_PFN_COMPOUND)) {
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
}
}
if (folio_is_device_private(newfolio) ||
folio_is_device_coherent(newfolio)) {
if (mapping) {
/*
* For now only support anonymous memory migrating to
* device private or coherent memory.
*
* Try to get rid of swap cache if possible.
*/
if (!folio_test_anon(folio) ||
!folio_free_swap(folio)) {
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
goto next;
}
}
} else if (folio_is_zone_device(newfolio)) {
/*
* Other types of ZONE_DEVICE page are not supported.
*/
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
goto next;
}
BUG_ON(folio_test_writeback(folio));
if (migrate && migrate->fault_page == page)
extra_cnt = 1;
for (j = 0; j < nr && i + j < npages; j++) {
folio = page_folio(migrate_pfn_to_page(src_pfns[i+j]));
newfolio = page_folio(migrate_pfn_to_page(dst_pfns[i+j]));
/*
* folio_free_swap() removed the folio from the swap
* cache. Refresh the saved mapping before migration.
*/
mapping = folio_mapping(folio);
r = folio_migrate_mapping(mapping, newfolio, folio, extra_cnt);
if (r)
src_pfns[i+j] &= ~MIGRATE_PFN_MIGRATE;
else
folio_migrate_flags(newfolio, folio);
}
next:
i += nr;
}
if (notified)
mmu_notifier_invalidate_range_end(&range);
}
/**
* migrate_device_pages() - migrate meta-data from src page to dst page
* @src_pfns: src_pfns returned from migrate_device_range()
* @dst_pfns: array of pfns allocated by the driver to migrate memory to
* @npages: number of pages in the range
*
* Equivalent to migrate_vma_pages(). This is called to migrate struct page
* meta-data from source struct page to destination.
*/
void migrate_device_pages(unsigned long *src_pfns, unsigned long *dst_pfns,
unsigned long npages)
{
__migrate_device_pages(src_pfns, dst_pfns, npages, NULL);
}
EXPORT_SYMBOL(migrate_device_pages);
/**
* migrate_vma_pages() - migrate meta-data from src page to dst page
* @migrate: migrate struct containing all migration information
*
* This migrates struct page meta-data from source struct page to destination
* struct page. This effectively finishes the migration from source page to the
* destination page.
*/
void migrate_vma_pages(struct migrate_vma *migrate)
{
__migrate_device_pages(migrate->src, migrate->dst, migrate->npages, migrate);
}
EXPORT_SYMBOL(migrate_vma_pages);
static void __migrate_device_finalize(unsigned long *src_pfns,
unsigned long *dst_pfns,
unsigned long npages,
struct page *fault_page)
{
struct folio *fault_folio = fault_page ?
page_folio(fault_page) : NULL;
unsigned long i;
for (i = 0; i < npages; i++) {
struct folio *dst = NULL, *src = NULL;
struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
struct page *page = migrate_pfn_to_page(src_pfns[i]);
if (newpage)
dst = page_folio(newpage);
if (!page) {
if (dst) {
WARN_ON_ONCE(fault_folio == dst);
folio_unlock(dst);
folio_put(dst);
}
continue;
}
src = page_folio(page);
if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE) || !dst) {
if (dst) {
WARN_ON_ONCE(fault_folio == dst);
folio_unlock(dst);
folio_put(dst);
}
dst = src;
}
if (!folio_is_zone_device(dst))
folio_add_lru(dst);
remove_migration_ptes(src, dst, 0);
if (fault_folio != src)
folio_unlock(src);
folio_put(src);
if (dst != src) {
WARN_ON_ONCE(fault_folio == dst);
folio_unlock(dst);
folio_put(dst);
}
}
}
/*
* migrate_device_finalize() - complete page migration
* @src_pfns: src_pfns returned from migrate_device_range()
* @dst_pfns: array of pfns allocated by the driver to migrate memory to
* @npages: number of pages in the range
*
* Completes migration of the page by removing special migration entries.
* Drivers must ensure copying of page data is complete and visible to the CPU
* before calling this.
*/
void migrate_device_finalize(unsigned long *src_pfns,
unsigned long *dst_pfns, unsigned long npages)
{
return __migrate_device_finalize(src_pfns, dst_pfns, npages, NULL);
}
EXPORT_SYMBOL(migrate_device_finalize);
/**
* migrate_vma_finalize() - restore CPU page table entry
* @migrate: migrate struct containing all migration information
*
* This replaces the special migration pte entry with either a mapping to the
* new page if migration was successful for that page, or to the original page
* otherwise.
*
* This also unlocks the pages and puts them back on the lru, or drops the extra
* refcount, for device pages.
*/
void migrate_vma_finalize(struct migrate_vma *migrate)
{
__migrate_device_finalize(migrate->src, migrate->dst, migrate->npages,
migrate->fault_page);
}
EXPORT_SYMBOL(migrate_vma_finalize);
static unsigned long migrate_device_pfn_lock(unsigned long pfn)
{
struct folio *folio;
folio = folio_get_nontail_page(pfn_to_page(pfn));
if (!folio)
return 0;
if (!folio_trylock(folio)) {
folio_put(folio);
return 0;
}
return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
}
/**
* migrate_device_range() - migrate device private pfns to normal memory.
* @src_pfns: array large enough to hold migrating source device private pfns.
* @start: starting pfn in the range to migrate.
* @npages: number of pages to migrate.
*
* migrate_vma_setup() is similar in concept to migrate_vma_setup() except that
* instead of looking up pages based on virtual address mappings a range of
* device pfns that should be migrated to system memory is used instead.
*
* This is useful when a driver needs to free device memory but doesn't know the
* virtual mappings of every page that may be in device memory. For example this
* is often the case when a driver is being unloaded or unbound from a device.
*
* Like migrate_vma_setup() this function will take a reference and lock any
* migrating pages that aren't free before unmapping them. Drivers may then
* allocate destination pages and start copying data from the device to CPU
* memory before calling migrate_device_pages().
*/
int migrate_device_range(unsigned long *src_pfns, unsigned long start,
unsigned long npages)
{
unsigned long i, j, pfn;
for (pfn = start, i = 0; i < npages; pfn++, i++) {
struct page *page = pfn_to_page(pfn);
struct folio *folio = page_folio(page);
unsigned int nr = 1;
src_pfns[i] = migrate_device_pfn_lock(pfn);
nr = folio_nr_pages(folio);
if (nr > 1) {
src_pfns[i] |= MIGRATE_PFN_COMPOUND;
for (j = 1; j < nr; j++)
src_pfns[i+j] = 0;
i += j - 1;
pfn += j - 1;
}
}
migrate_device_unmap(src_pfns, npages, NULL);
return 0;
}
EXPORT_SYMBOL(migrate_device_range);
/**
* migrate_device_pfns() - migrate device private pfns to normal memory.
* @src_pfns: pre-populated array of source device private pfns to migrate.
* @npages: number of pages to migrate.
*
* Similar to migrate_device_range() but supports non-contiguous pre-populated
* array of device pages to migrate.
*/
int migrate_device_pfns(unsigned long *src_pfns, unsigned long npages)
{
unsigned long i, j;
for (i = 0; i < npages; i++) {
struct page *page = pfn_to_page(src_pfns[i]);
struct folio *folio = page_folio(page);
unsigned int nr = 1;
src_pfns[i] = migrate_device_pfn_lock(src_pfns[i]);
nr = folio_nr_pages(folio);
if (nr > 1) {
src_pfns[i] |= MIGRATE_PFN_COMPOUND;
for (j = 1; j < nr; j++)
src_pfns[i+j] = 0;
i += j - 1;
}
}
migrate_device_unmap(src_pfns, npages, NULL);
return 0;
}
EXPORT_SYMBOL(migrate_device_pfns);
/*
* Migrate a device coherent folio back to normal memory. The caller should have
* a reference on folio which will be copied to the new folio if migration is
* successful or dropped on failure.
*/
int migrate_device_coherent_folio(struct folio *folio)
{
unsigned long src_pfn, dst_pfn = 0;
struct folio *dfolio;
WARN_ON_ONCE(folio_test_large(folio));
folio_lock(folio);
src_pfn = migrate_pfn(folio_pfn(folio)) | MIGRATE_PFN_MIGRATE;
/*
* We don't have a VMA and don't need to walk the page tables to find
* the source folio. So call migrate_vma_unmap() directly to unmap the
* folio as migrate_vma_setup() will fail if args.vma == NULL.
*/
migrate_device_unmap(&src_pfn, 1, NULL);
if (!(src_pfn & MIGRATE_PFN_MIGRATE))
return -EBUSY;
dfolio = folio_alloc(GFP_USER | __GFP_NOWARN, 0);
if (dfolio) {
folio_lock(dfolio);
dst_pfn = migrate_pfn(folio_pfn(dfolio));
}
migrate_device_pages(&src_pfn, &dst_pfn, 1);
if (src_pfn & MIGRATE_PFN_MIGRATE)
folio_copy(dfolio, folio);
migrate_device_finalize(&src_pfn, &dst_pfn, 1);
if (src_pfn & MIGRATE_PFN_MIGRATE)
return 0;
return -EBUSY;
}
