linux-stable/mm/migrate_device.c
Linus Torvalds df57721f9a Add x86 shadow stack support
Convert IBT selftest to asm to fix objtool warning
 -----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCgAdFiEEV76QKkVc4xCGURexaDWVMHDJkrAFAmTv1QQACgkQaDWVMHDJ
 krAUwhAAn6TOwHJK8BSkHeiQhON1nrlP3c5cv0AyZ2NP8RYDrZrSZvhpYBJ6wgKC
 Cx5CGq5nn9twYsYS3KsktLKDfR3lRdsQ7K9qtyFtYiaeaVKo+7gEKl/K+klwai8/
 gninQWHk0zmSCja8Vi77q52WOMkQKapT8+vaON9EVDO8dVEi+CvhAIfPwMafuiwO
 Rk4X86SzoZu9FP79LcCg9XyGC/XbM2OG9eNUTSCKT40qTTKm5y4gix687NvAlaHR
 ko5MTsdl0Wfp6Qk0ohT74LnoA2c1g/FluvZIM33ci/2rFpkf9Hw7ip3lUXqn6CPx
 rKiZ+pVRc0xikVWkraMfIGMJfUd2rhelp8OyoozD7DB7UZw40Q4RW4N5tgq9Fhe9
 MQs3p1v9N8xHdRKl365UcOczUxNAmv4u0nV5gY/4FMC6VjldCl2V9fmqYXyzFS4/
 Ogg4FSd7c2JyGFKPs+5uXyi+RY2qOX4+nzHOoKD7SY616IYqtgKoz5usxETLwZ6s
 VtJOmJL0h//z0A7tBliB0zd+SQ5UQQBDC2XouQH2fNX2isJMn0UDmWJGjaHgK6Hh
 8jVp6LNqf+CEQS387UxckOyj7fu438hDky1Ggaw4YqowEOhQeqLVO4++x+HITrbp
 AupXfbJw9h9cMN63Yc0gVxXQ9IMZ+M7UxLtZ3Cd8/PVztNy/clA=
 =3UUm
 -----END PGP SIGNATURE-----

Merge tag 'x86_shstk_for_6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 shadow stack support from Dave Hansen:
 "This is the long awaited x86 shadow stack support, part of Intel's
  Control-flow Enforcement Technology (CET).

  CET consists of two related security features: shadow stacks and
  indirect branch tracking. This series implements just the shadow stack
  part of this feature, and just for userspace.

  The main use case for shadow stack is providing protection against
  return oriented programming attacks. It works by maintaining a
  secondary (shadow) stack using a special memory type that has
  protections against modification. When executing a CALL instruction,
  the processor pushes the return address to both the normal stack and
  to the special permission shadow stack. Upon RET, the processor pops
  the shadow stack copy and compares it to the normal stack copy.

  For more information, refer to the links below for the earlier
  versions of this patch set"

Link: https://lore.kernel.org/lkml/20220130211838.8382-1-rick.p.edgecombe@intel.com/
Link: https://lore.kernel.org/lkml/20230613001108.3040476-1-rick.p.edgecombe@intel.com/

* tag 'x86_shstk_for_6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (47 commits)
  x86/shstk: Change order of __user in type
  x86/ibt: Convert IBT selftest to asm
  x86/shstk: Don't retry vm_munmap() on -EINTR
  x86/kbuild: Fix Documentation/ reference
  x86/shstk: Move arch detail comment out of core mm
  x86/shstk: Add ARCH_SHSTK_STATUS
  x86/shstk: Add ARCH_SHSTK_UNLOCK
  x86: Add PTRACE interface for shadow stack
  selftests/x86: Add shadow stack test
  x86/cpufeatures: Enable CET CR4 bit for shadow stack
  x86/shstk: Wire in shadow stack interface
  x86: Expose thread features in /proc/$PID/status
  x86/shstk: Support WRSS for userspace
  x86/shstk: Introduce map_shadow_stack syscall
  x86/shstk: Check that signal frame is shadow stack mem
  x86/shstk: Check that SSP is aligned on sigreturn
  x86/shstk: Handle signals for shadow stack
  x86/shstk: Introduce routines modifying shstk
  x86/shstk: Handle thread shadow stack
  x86/shstk: Add user-mode shadow stack support
  ...
2023-08-31 12:20:12 -07:00

960 lines
27 KiB
C

// 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/swapops.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);
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;
}
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;
pte_t *ptep;
again:
if (pmd_none(*pmdp))
return migrate_vma_collect_hole(start, end, -1, walk);
if (pmd_trans_huge(*pmdp)) {
struct page *page;
ptl = pmd_lock(mm, pmdp);
if (unlikely(!pmd_trans_huge(*pmdp))) {
spin_unlock(ptl);
goto again;
}
page = pmd_page(*pmdp);
if (is_huge_zero_page(page)) {
spin_unlock(ptl);
split_huge_pmd(vma, pmdp, addr);
} else {
int ret;
get_page(page);
spin_unlock(ptl);
if (unlikely(!trylock_page(page)))
return migrate_vma_collect_skip(start, end,
walk);
ret = split_huge_page(page);
unlock_page(page);
put_page(page);
if (ret)
return migrate_vma_collect_skip(start, end,
walk);
}
}
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
if (!ptep)
goto again;
arch_enter_lazy_mmu_mode();
for (; addr < end; addr += PAGE_SIZE, ptep++) {
unsigned long mpfn = 0, pfn;
struct page *page;
swp_entry_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 = pte_to_swp_entry(pte);
if (!is_device_private_entry(entry))
goto next;
page = pfn_swap_entry_to_page(entry);
if (!(migrate->flags &
MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
page->pgmap->owner != migrate->pgmap_owner)
goto next;
mpfn = migrate_pfn(page_to_pfn(page)) |
MIGRATE_PFN_MIGRATE;
if (is_writable_device_private_entry(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) &&
(!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
page->pgmap->owner != migrate->pgmap_owner))
goto next;
mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
}
/* FIXME support THP */
if (!page || !page->mapping || PageTransCompound(page)) {
mpfn = 0;
goto next;
}
/*
* By getting a reference on the page 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 page from the lru
* for non device page (device page are not on the lru and thus
* can't be dropped from it).
*/
get_page(page);
/*
* We rely on trylock_page() to avoid deadlock between
* concurrent migrations where each is waiting on the others
* page lock. If we can't immediately lock the page we fail this
* migration as it is only best effort anyway.
*
* If we can lock the page it's safe to set up a migration entry
* now. In the common case where the page 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 (trylock_page(page)) {
bool anon_exclusive;
pte_t swp_pte;
flush_cache_page(vma, addr, pte_pfn(pte));
anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
if (anon_exclusive) {
pte = ptep_clear_flush(vma, addr, ptep);
if (page_try_share_anon_rmap(page)) {
set_pte_at(mm, addr, ptep, pte);
unlock_page(page);
put_page(page);
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_dirty(pte))
folio_mark_dirty(page_folio(page));
/* 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_wp(pte))
swp_pte = pte_swp_mkuffd_wp(swp_pte);
} else {
if (pte_swp_soft_dirty(pte))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
if (pte_swp_uffd_wp(pte))
swp_pte = pte_swp_mkuffd_wp(swp_pte);
}
set_pte_at(mm, addr, ptep, swp_pte);
/*
* This is like regular unmap: we remove the rmap and
* drop page refcount. Page won't be freed, as we took
* a reference just above.
*/
page_remove_rmap(page, vma, false);
put_page(page);
if (pte_present(pte))
unmapped++;
} else {
put_page(page);
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);
arch_leave_lazy_mmu_mode();
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(migrate->vma->vm_mm, 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)
{
/*
* One extra ref because caller holds an extra reference, either from
* isolate_lru_page() for a regular page, or migrate_vma_collect() for
* a device page.
*/
int extra = 1 + (page == fault_page);
/*
* FIXME support THP (transparent huge page), it is bit more complex to
* check them than regular pages, because they can be mapped with a pmd
* or with a pte (split pte mapping).
*/
if (PageCompound(page))
return false;
/* Page from ZONE_DEVICE have one extra reference */
if (is_zone_device_page(page))
extra++;
/* For file back page */
if (page_mapping(page))
extra += 1 + page_has_private(page);
if ((page_count(page) - extra) > page_mapcount(page))
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)
{
unsigned long i, restore = 0;
bool allow_drain = true;
unsigned long unmapped = 0;
lru_add_drain();
for (i = 0; i < npages; i++) {
struct page *page = migrate_pfn_to_page(src_pfns[i]);
struct folio *folio;
if (!page) {
if (src_pfns[i] & MIGRATE_PFN_MIGRATE)
unmapped++;
continue;
}
/* ZONE_DEVICE pages are not on LRU */
if (!is_zone_device_page(page)) {
if (!PageLRU(page) && allow_drain) {
/* Drain CPU's lru cache */
lru_add_drain_all();
allow_drain = false;
}
if (!isolate_lru_page(page)) {
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
restore++;
continue;
}
/* Drop the reference we took in collect */
put_page(page);
}
folio = page_folio(page);
if (folio_mapped(folio))
try_to_migrate(folio, 0);
if (page_mapped(page) ||
!migrate_vma_check_page(page, fault_page)) {
if (!is_zone_device_page(page)) {
get_page(page);
putback_lru_page(page);
}
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
restore++;
continue;
}
unmapped++;
}
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, false);
src_pfns[i] = 0;
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;
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);
/*
* 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,
struct page *page,
unsigned long *src)
{
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 (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
goto abort;
if (pte_alloc(mm, pmdp))
goto abort;
if (unlikely(anon_vma_prepare(vma)))
goto abort;
if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
goto abort;
/*
* The memory barrier inside __SetPageUptodate makes sure that
* preceding stores to the page contents become visible before
* the set_pte_at() write.
*/
__SetPageUptodate(page);
if (is_device_private_page(page)) {
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 (is_zone_device_page(page) &&
!is_device_coherent_page(page)) {
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);
page_add_new_anon_rmap(page, vma, addr);
if (!is_zone_device_page(page))
lru_cache_add_inactive_or_unevictable(page, vma);
get_page(page);
if (flush) {
flush_cache_page(vma, addr, pte_pfn(orig_pte));
ptep_clear_flush(vma, addr, ptep);
set_pte_at_notify(mm, addr, ptep, entry);
update_mmu_cache(vma, addr, ptep);
} else {
/* No need to invalidate - it was non-present before */
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;
bool notified = false;
for (i = 0; i < npages; i++) {
struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
struct page *page = migrate_pfn_to_page(src_pfns[i]);
struct address_space *mapping;
int r;
if (!newpage) {
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
continue;
}
if (!page) {
unsigned long addr;
if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE))
continue;
/*
* The only time there is no vma is when called from
* migrate_device_coherent_page(). 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);
}
migrate_vma_insert_page(migrate, addr, newpage,
&src_pfns[i]);
continue;
}
mapping = page_mapping(page);
if (is_device_private_page(newpage) ||
is_device_coherent_page(newpage)) {
if (mapping) {
struct folio *folio;
folio = page_folio(page);
/*
* 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;
continue;
}
}
} else if (is_zone_device_page(newpage)) {
/*
* Other types of ZONE_DEVICE page are not supported.
*/
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
continue;
}
if (migrate && migrate->fault_page == page)
r = migrate_folio_extra(mapping, page_folio(newpage),
page_folio(page),
MIGRATE_SYNC_NO_COPY, 1);
else
r = migrate_folio(mapping, page_folio(newpage),
page_folio(page), MIGRATE_SYNC_NO_COPY);
if (r != MIGRATEPAGE_SUCCESS)
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
}
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);
/*
* 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)
{
unsigned long i;
for (i = 0; i < npages; i++) {
struct folio *dst, *src;
struct page *newpage = migrate_pfn_to_page(dst_pfns[i]);
struct page *page = migrate_pfn_to_page(src_pfns[i]);
if (!page) {
if (newpage) {
unlock_page(newpage);
put_page(newpage);
}
continue;
}
if (!(src_pfns[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
if (newpage) {
unlock_page(newpage);
put_page(newpage);
}
newpage = page;
}
src = page_folio(page);
dst = page_folio(newpage);
remove_migration_ptes(src, dst, false);
folio_unlock(src);
if (is_zone_device_page(page))
put_page(page);
else
putback_lru_page(page);
if (newpage != page) {
unlock_page(newpage);
if (is_zone_device_page(newpage))
put_page(newpage);
else
putback_lru_page(newpage);
}
}
}
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);
}
EXPORT_SYMBOL(migrate_vma_finalize);
/**
* 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, pfn;
for (pfn = start, i = 0; i < npages; pfn++, i++) {
struct page *page = pfn_to_page(pfn);
if (!get_page_unless_zero(page)) {
src_pfns[i] = 0;
continue;
}
if (!trylock_page(page)) {
src_pfns[i] = 0;
put_page(page);
continue;
}
src_pfns[i] = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
}
migrate_device_unmap(src_pfns, npages, NULL);
return 0;
}
EXPORT_SYMBOL(migrate_device_range);
/*
* Migrate a device coherent page back to normal memory. The caller should have
* a reference on page which will be copied to the new page if migration is
* successful or dropped on failure.
*/
int migrate_device_coherent_page(struct page *page)
{
unsigned long src_pfn, dst_pfn = 0;
struct page *dpage;
WARN_ON_ONCE(PageCompound(page));
lock_page(page);
src_pfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE;
/*
* We don't have a VMA and don't need to walk the page tables to find
* the source page. So call migrate_vma_unmap() directly to unmap the
* page 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;
dpage = alloc_page(GFP_USER | __GFP_NOWARN);
if (dpage) {
lock_page(dpage);
dst_pfn = migrate_pfn(page_to_pfn(dpage));
}
migrate_device_pages(&src_pfn, &dst_pfn, 1);
if (src_pfn & MIGRATE_PFN_MIGRATE)
copy_highpage(dpage, page);
migrate_device_finalize(&src_pfn, &dst_pfn, 1);
if (src_pfn & MIGRATE_PFN_MIGRATE)
return 0;
return -EBUSY;
}