hmm.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright 2013 Red Hat Inc.
*
* Authors: Jérôme Glisse <jglisse@redhat.com>
*/
/*
* Refer to include/linux/hmm.h for information about heterogeneous memory
* management or HMM for short.
*/
#include <linux/mm.h>
#include <linux/hmm.h>
#include <linux/init.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/mmzone.h>
#include <linux/pagemap.h>
#include <linux/swapops.h>
#include <linux/hugetlb.h>
#include <linux/memremap.h>
#include <linux/sched/mm.h>
#include <linux/jump_label.h>
#include <linux/dma-mapping.h>
#include <linux/mmu_notifier.h>
#include <linux/memory_hotplug.h>
static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
/**
* hmm_get_or_create - register HMM against an mm (HMM internal)
*
* @mm: mm struct to attach to
* Returns: returns an HMM object, either by referencing the existing
* (per-process) object, or by creating a new one.
*
* This is not intended to be used directly by device drivers. If mm already
* has an HMM struct then it get a reference on it and returns it. Otherwise
* it allocates an HMM struct, initializes it, associate it with the mm and
* returns it.
*/
static struct hmm *hmm_get_or_create(struct mm_struct *mm)
{
struct hmm *hmm;
lockdep_assert_held_write(&mm->mmap_sem);
/* Abuse the page_table_lock to also protect mm->hmm. */
spin_lock(&mm->page_table_lock);
hmm = mm->hmm;
if (mm->hmm && kref_get_unless_zero(&mm->hmm->kref))
goto out_unlock;
spin_unlock(&mm->page_table_lock);
hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
if (!hmm)
return NULL;
init_waitqueue_head(&hmm->wq);
INIT_LIST_HEAD(&hmm->mirrors);
init_rwsem(&hmm->mirrors_sem);
hmm->mmu_notifier.ops = NULL;
INIT_LIST_HEAD(&hmm->ranges);
spin_lock_init(&hmm->ranges_lock);
kref_init(&hmm->kref);
hmm->notifiers = 0;
hmm->mm = mm;
hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) {
kfree(hmm);
return NULL;
}
mmgrab(hmm->mm);
/*
* We hold the exclusive mmap_sem here so we know that mm->hmm is
* still NULL or 0 kref, and is safe to update.
*/
spin_lock(&mm->page_table_lock);
mm->hmm = hmm;
out_unlock:
spin_unlock(&mm->page_table_lock);
return hmm;
}
static void hmm_free_rcu(struct rcu_head *rcu)
{
struct hmm *hmm = container_of(rcu, struct hmm, rcu);
mmdrop(hmm->mm);
kfree(hmm);
}
static void hmm_free(struct kref *kref)
{
struct hmm *hmm = container_of(kref, struct hmm, kref);
spin_lock(&hmm->mm->page_table_lock);
if (hmm->mm->hmm == hmm)
hmm->mm->hmm = NULL;
spin_unlock(&hmm->mm->page_table_lock);
mmu_notifier_unregister_no_release(&hmm->mmu_notifier, hmm->mm);
mmu_notifier_call_srcu(&hmm->rcu, hmm_free_rcu);
}
static inline void hmm_put(struct hmm *hmm)
{
kref_put(&hmm->kref, hmm_free);
}
static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
{
struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
struct hmm_mirror *mirror;
/* Bail out if hmm is in the process of being freed */
if (!kref_get_unless_zero(&hmm->kref))
return;
/*
* Since hmm_range_register() holds the mmget() lock hmm_release() is
* prevented as long as a range exists.
*/
WARN_ON(!list_empty_careful(&hmm->ranges));
down_read(&hmm->mirrors_sem);
list_for_each_entry(mirror, &hmm->mirrors, list) {
/*
* Note: The driver is not allowed to trigger
* hmm_mirror_unregister() from this thread.
*/
if (mirror->ops->release)
mirror->ops->release(mirror);
}
up_read(&hmm->mirrors_sem);
hmm_put(hmm);
}
static void notifiers_decrement(struct hmm *hmm)
{
unsigned long flags;
spin_lock_irqsave(&hmm->ranges_lock, flags);
hmm->notifiers--;
if (!hmm->notifiers) {
struct hmm_range *range;
list_for_each_entry(range, &hmm->ranges, list) {
if (range->valid)
continue;
range->valid = true;
}
wake_up_all(&hmm->wq);
}
spin_unlock_irqrestore(&hmm->ranges_lock, flags);
}
static int hmm_invalidate_range_start(struct mmu_notifier *mn,
const struct mmu_notifier_range *nrange)
{
struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
struct hmm_mirror *mirror;
struct hmm_update update;
struct hmm_range *range;
unsigned long flags;
int ret = 0;
if (!kref_get_unless_zero(&hmm->kref))
return 0;
update.start = nrange->start;
update.end = nrange->end;
update.event = HMM_UPDATE_INVALIDATE;
update.blockable = mmu_notifier_range_blockable(nrange);
spin_lock_irqsave(&hmm->ranges_lock, flags);
hmm->notifiers++;
list_for_each_entry(range, &hmm->ranges, list) {
if (update.end < range->start || update.start >= range->end)
continue;
range->valid = false;
}
spin_unlock_irqrestore(&hmm->ranges_lock, flags);
if (mmu_notifier_range_blockable(nrange))
down_read(&hmm->mirrors_sem);
else if (!down_read_trylock(&hmm->mirrors_sem)) {
ret = -EAGAIN;
goto out;
}
list_for_each_entry(mirror, &hmm->mirrors, list) {
int rc;
rc = mirror->ops->sync_cpu_device_pagetables(mirror, &update);
if (rc) {
if (WARN_ON(update.blockable || rc != -EAGAIN))
continue;
ret = -EAGAIN;
break;
}
}
up_read(&hmm->mirrors_sem);
out:
if (ret)
notifiers_decrement(hmm);
hmm_put(hmm);
return ret;
}
static void hmm_invalidate_range_end(struct mmu_notifier *mn,
const struct mmu_notifier_range *nrange)
{
struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
if (!kref_get_unless_zero(&hmm->kref))
return;
notifiers_decrement(hmm);
hmm_put(hmm);
}
static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
.release = hmm_release,
.invalidate_range_start = hmm_invalidate_range_start,
.invalidate_range_end = hmm_invalidate_range_end,
};
/*
* hmm_mirror_register() - register a mirror against an mm
*
* @mirror: new mirror struct to register
* @mm: mm to register against
* Return: 0 on success, -ENOMEM if no memory, -EINVAL if invalid arguments
*
* To start mirroring a process address space, the device driver must register
* an HMM mirror struct.
*/
int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
{
lockdep_assert_held_write(&mm->mmap_sem);
/* Sanity check */
if (!mm || !mirror || !mirror->ops)
return -EINVAL;
mirror->hmm = hmm_get_or_create(mm);
if (!mirror->hmm)
return -ENOMEM;
down_write(&mirror->hmm->mirrors_sem);
list_add(&mirror->list, &mirror->hmm->mirrors);
up_write(&mirror->hmm->mirrors_sem);
return 0;
}
EXPORT_SYMBOL(hmm_mirror_register);
/*
* hmm_mirror_unregister() - unregister a mirror
*
* @mirror: mirror struct to unregister
*
* Stop mirroring a process address space, and cleanup.
*/
void hmm_mirror_unregister(struct hmm_mirror *mirror)
{
struct hmm *hmm = mirror->hmm;
down_write(&hmm->mirrors_sem);
list_del(&mirror->list);
up_write(&hmm->mirrors_sem);
hmm_put(hmm);
}
EXPORT_SYMBOL(hmm_mirror_unregister);
struct hmm_vma_walk {
struct hmm_range *range;
struct dev_pagemap *pgmap;
unsigned long last;
bool fault;
bool block;
};
static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
bool write_fault, uint64_t *pfn)
{
unsigned int flags = FAULT_FLAG_REMOTE;
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
vm_fault_t ret;
flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
flags |= write_fault ? FAULT_FLAG_WRITE : 0;
ret = handle_mm_fault(vma, addr, flags);
if (ret & VM_FAULT_RETRY)
return -EAGAIN;
if (ret & VM_FAULT_ERROR) {
*pfn = range->values[HMM_PFN_ERROR];
return -EFAULT;
}
return -EBUSY;
}
static int hmm_pfns_bad(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
uint64_t *pfns = range->pfns;
unsigned long i;
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, i++)
pfns[i] = range->values[HMM_PFN_ERROR];
return 0;
}
/*
* hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
* @start: range virtual start address (inclusive)
* @end: range virtual end address (exclusive)
* @fault: should we fault or not ?
* @write_fault: write fault ?
* @walk: mm_walk structure
* Return: 0 on success, -EBUSY after page fault, or page fault error
*
* This function will be called whenever pmd_none() or pte_none() returns true,
* or whenever there is no page directory covering the virtual address range.
*/
static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
bool fault, bool write_fault,
struct mm_walk *walk)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
uint64_t *pfns = range->pfns;
unsigned long i, page_size;
hmm_vma_walk->last = addr;
page_size = hmm_range_page_size(range);
i = (addr - range->start) >> range->page_shift;
for (; addr < end; addr += page_size, i++) {
pfns[i] = range->values[HMM_PFN_NONE];
if (fault || write_fault) {
int ret;
ret = hmm_vma_do_fault(walk, addr, write_fault,
&pfns[i]);
if (ret != -EBUSY)
return ret;
}
}
return (fault || write_fault) ? -EBUSY : 0;
}
static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
uint64_t pfns, uint64_t cpu_flags,
bool *fault, bool *write_fault)
{
struct hmm_range *range = hmm_vma_walk->range;
if (!hmm_vma_walk->fault)
return;
/*
* So we not only consider the individual per page request we also
* consider the default flags requested for the range. The API can
* be use in 2 fashions. The first one where the HMM user coalesce
* multiple page fault into one request and set flags per pfns for
* of those faults. The second one where the HMM user want to pre-
* fault a range with specific flags. For the latter one it is a
* waste to have the user pre-fill the pfn arrays with a default
* flags value.
*/
pfns = (pfns & range->pfn_flags_mask) | range->default_flags;
/* We aren't ask to do anything ... */
if (!(pfns & range->flags[HMM_PFN_VALID]))
return;
/* If this is device memory than only fault if explicitly requested */
if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
/* Do we fault on device memory ? */
if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
*write_fault = pfns & range->flags[HMM_PFN_WRITE];
*fault = true;
}
return;
}
/* If CPU page table is not valid then we need to fault */
*fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
/* Need to write fault ? */
if ((pfns & range->flags[HMM_PFN_WRITE]) &&
!(cpu_flags & range->flags[HMM_PFN_WRITE])) {
*write_fault = true;
*fault = true;
}
}
static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
const uint64_t *pfns, unsigned long npages,
uint64_t cpu_flags, bool *fault,
bool *write_fault)
{
unsigned long i;
if (!hmm_vma_walk->fault) {
*fault = *write_fault = false;
return;
}
*fault = *write_fault = false;
for (i = 0; i < npages; ++i) {
hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
fault, write_fault);
if ((*write_fault))
return;
}
}
static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
bool fault, write_fault;
unsigned long i, npages;
uint64_t *pfns;
i = (addr - range->start) >> PAGE_SHIFT;
npages = (end - addr) >> PAGE_SHIFT;
pfns = &range->pfns[i];
hmm_range_need_fault(hmm_vma_walk, pfns, npages,
0, &fault, &write_fault);
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
}
static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
{
if (pmd_protnone(pmd))
return 0;
return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
range->flags[HMM_PFN_WRITE] :
range->flags[HMM_PFN_VALID];
}
static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud)
{
if (!pud_present(pud))
return 0;
return pud_write(pud) ? range->flags[HMM_PFN_VALID] |
range->flags[HMM_PFN_WRITE] :
range->flags[HMM_PFN_VALID];
}
static int hmm_vma_handle_pmd(struct mm_walk *walk,
unsigned long addr,
unsigned long end,
uint64_t *pfns,
pmd_t pmd)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
unsigned long pfn, npages, i;
bool fault, write_fault;
uint64_t cpu_flags;
npages = (end - addr) >> PAGE_SHIFT;
cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
&fault, &write_fault);
if (pmd_protnone(pmd) || fault || write_fault)
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
pfn = pmd_pfn(pmd) + pte_index(addr);
for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
if (pmd_devmap(pmd)) {
hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
hmm_vma_walk->pgmap);
if (unlikely(!hmm_vma_walk->pgmap))
return -EBUSY;
}
pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags;
}
if (hmm_vma_walk->pgmap) {
put_dev_pagemap(hmm_vma_walk->pgmap);
hmm_vma_walk->pgmap = NULL;
}
hmm_vma_walk->last = end;
return 0;
#else
/* If THP is not enabled then we should never reach that code ! */
return -EINVAL;
#endif
}
static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
{
if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
return 0;
return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
range->flags[HMM_PFN_WRITE] :
range->flags[HMM_PFN_VALID];
}
static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
unsigned long end, pmd_t *pmdp, pte_t *ptep,
uint64_t *pfn)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
bool fault, write_fault;
uint64_t cpu_flags;
pte_t pte = *ptep;
uint64_t orig_pfn = *pfn;
*pfn = range->values[HMM_PFN_NONE];
fault = write_fault = false;
if (pte_none(pte)) {
hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0,
&fault, &write_fault);
if (fault || write_fault)
goto fault;
return 0;
}
if (!pte_present(pte)) {
swp_entry_t entry = pte_to_swp_entry(pte);
if (!non_swap_entry(entry)) {
if (fault || write_fault)
goto fault;
return 0;
}
/*
* This is a special swap entry, ignore migration, use
* device and report anything else as error.
*/
if (is_device_private_entry(entry)) {
cpu_flags = range->flags[HMM_PFN_VALID] |
range->flags[HMM_PFN_DEVICE_PRIVATE];
cpu_flags |= is_write_device_private_entry(entry) ?
range->flags[HMM_PFN_WRITE] : 0;
hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
&fault, &write_fault);
if (fault || write_fault)
goto fault;
*pfn = hmm_device_entry_from_pfn(range,
swp_offset(entry));
*pfn |= cpu_flags;
return 0;
}
if (is_migration_entry(entry)) {
if (fault || write_fault) {
pte_unmap(ptep);
hmm_vma_walk->last = addr;
migration_entry_wait(vma->vm_mm,
pmdp, addr);
return -EBUSY;
}
return 0;
}
/* Report error for everything else */
*pfn = range->values[HMM_PFN_ERROR];
return -EFAULT;
} else {
cpu_flags = pte_to_hmm_pfn_flags(range, pte);
hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
&fault, &write_fault);
}
if (fault || write_fault)
goto fault;
if (pte_devmap(pte)) {
hmm_vma_walk->pgmap = get_dev_pagemap(pte_pfn(pte),
hmm_vma_walk->pgmap);
if (unlikely(!hmm_vma_walk->pgmap))
return -EBUSY;
} else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
*pfn = range->values[HMM_PFN_SPECIAL];
return -EFAULT;
}
*pfn = hmm_device_entry_from_pfn(range, pte_pfn(pte)) | cpu_flags;
return 0;
fault:
if (hmm_vma_walk->pgmap) {
put_dev_pagemap(hmm_vma_walk->pgmap);
hmm_vma_walk->pgmap = NULL;
}
pte_unmap(ptep);
/* Fault any virtual address we were asked to fault */
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
}
static int hmm_vma_walk_pmd(pmd_t *pmdp,
unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
uint64_t *pfns = range->pfns;
unsigned long addr = start, i;
pte_t *ptep;
pmd_t pmd;
again:
pmd = READ_ONCE(*pmdp);
if (pmd_none(pmd))
return hmm_vma_walk_hole(start, end, walk);
if (pmd_huge(pmd) && (range->vma->vm_flags & VM_HUGETLB))
return hmm_pfns_bad(start, end, walk);
if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
bool fault, write_fault;
unsigned long npages;
uint64_t *pfns;
i = (addr - range->start) >> PAGE_SHIFT;
npages = (end - addr) >> PAGE_SHIFT;
pfns = &range->pfns[i];
hmm_range_need_fault(hmm_vma_walk, pfns, npages,
0, &fault, &write_fault);
if (fault || write_fault) {
hmm_vma_walk->last = addr;
pmd_migration_entry_wait(vma->vm_mm, pmdp);
return -EBUSY;
}
return 0;
} else if (!pmd_present(pmd))
return hmm_pfns_bad(start, end, walk);
if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
/*
* No need to take pmd_lock here, even if some other threads
* is splitting the huge pmd we will get that event through
* mmu_notifier callback.
*
* So just read pmd value and check again its a transparent
* huge or device mapping one and compute corresponding pfn
* values.
*/
pmd = pmd_read_atomic(pmdp);
barrier();
if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
goto again;
i = (addr - range->start) >> PAGE_SHIFT;
return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
}
/*
* We have handled all the valid case above ie either none, migration,
* huge or transparent huge. At this point either it is a valid pmd
* entry pointing to pte directory or it is a bad pmd that will not
* recover.
*/
if (pmd_bad(pmd))
return hmm_pfns_bad(start, end, walk);
ptep = pte_offset_map(pmdp, addr);
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
int r;
r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
if (r) {
/* hmm_vma_handle_pte() did unmap pte directory */
hmm_vma_walk->last = addr;
return r;
}
}
if (hmm_vma_walk->pgmap) {
/*
* We do put_dev_pagemap() here and not in hmm_vma_handle_pte()
* so that we can leverage get_dev_pagemap() optimization which
* will not re-take a reference on a pgmap if we already have
* one.
*/
put_dev_pagemap(hmm_vma_walk->pgmap);
hmm_vma_walk->pgmap = NULL;
}
pte_unmap(ptep - 1);
hmm_vma_walk->last = addr;
return 0;
}
static int hmm_vma_walk_pud(pud_t *pudp,
unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
unsigned long addr = start, next;
pmd_t *pmdp;
pud_t pud;
int ret;
again:
pud = READ_ONCE(*pudp);
if (pud_none(pud))
return hmm_vma_walk_hole(start, end, walk);
if (pud_huge(pud) && pud_devmap(pud)) {
unsigned long i, npages, pfn;
uint64_t *pfns, cpu_flags;
bool fault, write_fault;
if (!pud_present(pud))
return hmm_vma_walk_hole(start, end, walk);
i = (addr - range->start) >> PAGE_SHIFT;
npages = (end - addr) >> PAGE_SHIFT;
pfns = &range->pfns[i];
cpu_flags = pud_to_hmm_pfn_flags(range, pud);
hmm_range_need_fault(hmm_vma_walk, pfns, npages,
cpu_flags, &fault, &write_fault);
if (fault || write_fault)
return hmm_vma_walk_hole_(addr, end, fault,
write_fault, walk);
pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
for (i = 0; i < npages; ++i, ++pfn) {
hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
hmm_vma_walk->pgmap);
if (unlikely(!hmm_vma_walk->pgmap))
return -EBUSY;
pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
cpu_flags;
}
if (hmm_vma_walk->pgmap) {
put_dev_pagemap(hmm_vma_walk->pgmap);
hmm_vma_walk->pgmap = NULL;
}
hmm_vma_walk->last = end;
return 0;
}
split_huge_pud(walk->vma, pudp, addr);
if (pud_none(*pudp))
goto again;
pmdp = pmd_offset(pudp, addr);
do {
next = pmd_addr_end(addr, end);
ret = hmm_vma_walk_pmd(pmdp, addr, next, walk);
if (ret)
return ret;
} while (pmdp++, addr = next, addr != end);
return 0;
}
static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
unsigned long start, unsigned long end,
struct mm_walk *walk)
{
#ifdef CONFIG_HUGETLB_PAGE
unsigned long addr = start, i, pfn, mask, size, pfn_inc;
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
struct hstate *h = hstate_vma(vma);
uint64_t orig_pfn, cpu_flags;
bool fault, write_fault;
spinlock_t *ptl;
pte_t entry;
int ret = 0;
size = 1UL << huge_page_shift(h);
mask = size - 1;
if (range->page_shift != PAGE_SHIFT) {
/* Make sure we are looking at full page. */
if (start & mask)
return -EINVAL;
if (end < (start + size))
return -EINVAL;
pfn_inc = size >> PAGE_SHIFT;
} else {
pfn_inc = 1;
size = PAGE_SIZE;
}
ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
entry = huge_ptep_get(pte);
i = (start - range->start) >> range->page_shift;
orig_pfn = range->pfns[i];
range->pfns[i] = range->values[HMM_PFN_NONE];
cpu_flags = pte_to_hmm_pfn_flags(range, entry);
fault = write_fault = false;
hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
&fault, &write_fault);
if (fault || write_fault) {
ret = -ENOENT;
goto unlock;
}
pfn = pte_pfn(entry) + ((start & mask) >> range->page_shift);
for (; addr < end; addr += size, i++, pfn += pfn_inc)
range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
cpu_flags;
hmm_vma_walk->last = end;
unlock:
spin_unlock(ptl);
if (ret == -ENOENT)
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
return ret;
#else /* CONFIG_HUGETLB_PAGE */
return -EINVAL;
#endif
}
static void hmm_pfns_clear(struct hmm_range *range,
uint64_t *pfns,
unsigned long addr,
unsigned long end)
{
for (; addr < end; addr += PAGE_SIZE, pfns++)
*pfns = range->values[HMM_PFN_NONE];
}
/*
* hmm_range_register() - start tracking change to CPU page table over a range
* @range: range
* @mm: the mm struct for the range of virtual address
* @start: start virtual address (inclusive)
* @end: end virtual address (exclusive)
* @page_shift: expect page shift for the range
* Returns 0 on success, -EFAULT if the address space is no longer valid
*
* Track updates to the CPU page table see include/linux/hmm.h
*/
int hmm_range_register(struct hmm_range *range,
struct hmm_mirror *mirror,
unsigned long start,
unsigned long end,
unsigned page_shift)
{
unsigned long mask = ((1UL << page_shift) - 1UL);
struct hmm *hmm = mirror->hmm;
unsigned long flags;
range->valid = false;
range->hmm = NULL;
if ((start & mask) || (end & mask))
return -EINVAL;
if (start >= end)
return -EINVAL;
range->page_shift = page_shift;
range->start = start;
range->end = end;
/* Prevent hmm_release() from running while the range is valid */
if (!mmget_not_zero(hmm->mm))
return -EFAULT;
/* Initialize range to track CPU page table updates. */
spin_lock_irqsave(&hmm->ranges_lock, flags);
range->hmm = hmm;
kref_get(&hmm->kref);
list_add(&range->list, &hmm->ranges);
/*
* If there are any concurrent notifiers we have to wait for them for
* the range to be valid (see hmm_range_wait_until_valid()).
*/
if (!hmm->notifiers)
range->valid = true;
spin_unlock_irqrestore(&hmm->ranges_lock, flags);
return 0;
}
EXPORT_SYMBOL(hmm_range_register);
/*
* hmm_range_unregister() - stop tracking change to CPU page table over a range
* @range: range
*
* Range struct is used to track updates to the CPU page table after a call to
* hmm_range_register(). See include/linux/hmm.h for how to use it.
*/
void hmm_range_unregister(struct hmm_range *range)
{
struct hmm *hmm = range->hmm;
unsigned long flags;
spin_lock_irqsave(&hmm->ranges_lock, flags);
list_del_init(&range->list);
spin_unlock_irqrestore(&hmm->ranges_lock, flags);
/* Drop reference taken by hmm_range_register() */
mmput(hmm->mm);
hmm_put(hmm);
/*
* The range is now invalid and the ref on the hmm is dropped, so
* poison the pointer. Leave other fields in place, for the caller's
* use.
*/
range->valid = false;
memset(&range->hmm, POISON_INUSE, sizeof(range->hmm));
}
EXPORT_SYMBOL(hmm_range_unregister);
/*
* hmm_range_snapshot() - snapshot CPU page table for a range
* @range: range
* Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
* permission (for instance asking for write and range is read only),
* -EBUSY if you need to retry, -EFAULT invalid (ie either no valid
* vma or it is illegal to access that range), number of valid pages
* in range->pfns[] (from range start address).
*
* This snapshots the CPU page table for a range of virtual addresses. Snapshot
* validity is tracked by range struct. See in include/linux/hmm.h for example
* on how to use.
*/
long hmm_range_snapshot(struct hmm_range *range)
{
const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
unsigned long start = range->start, end;
struct hmm_vma_walk hmm_vma_walk;
struct hmm *hmm = range->hmm;
struct vm_area_struct *vma;
struct mm_walk mm_walk;
lockdep_assert_held(&hmm->mm->mmap_sem);
do {
/* If range is no longer valid force retry. */
if (!range->valid)
return -EBUSY;
vma = find_vma(hmm->mm, start);
if (vma == NULL || (vma->vm_flags & device_vma))
return -EFAULT;
if (is_vm_hugetlb_page(vma)) {
if (huge_page_shift(hstate_vma(vma)) !=
range->page_shift &&
range->page_shift != PAGE_SHIFT)
return -EINVAL;
} else {
if (range->page_shift != PAGE_SHIFT)
return -EINVAL;
}
if (!(vma->vm_flags & VM_READ)) {
/*
* If vma do not allow read access, then assume that it
* does not allow write access, either. HMM does not
* support architecture that allow write without read.
*/
hmm_pfns_clear(range, range->pfns,
range->start, range->end);
return -EPERM;
}
range->vma = vma;
hmm_vma_walk.pgmap = NULL;
hmm_vma_walk.last = start;
hmm_vma_walk.fault = false;
hmm_vma_walk.range = range;
mm_walk.private = &hmm_vma_walk;
end = min(range->end, vma->vm_end);
mm_walk.vma = vma;
mm_walk.mm = vma->vm_mm;
mm_walk.pte_entry = NULL;
mm_walk.test_walk = NULL;
mm_walk.hugetlb_entry = NULL;
mm_walk.pud_entry = hmm_vma_walk_pud;
mm_walk.pmd_entry = hmm_vma_walk_pmd;
mm_walk.pte_hole = hmm_vma_walk_hole;
mm_walk.hugetlb_entry = hmm_vma_walk_hugetlb_entry;
walk_page_range(start, end, &mm_walk);
start = end;
} while (start < range->end);
return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
}
EXPORT_SYMBOL(hmm_range_snapshot);
/*
* hmm_range_fault() - try to fault some address in a virtual address range
* @range: range being faulted
* @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
* Return: number of valid pages in range->pfns[] (from range start
* address). This may be zero. If the return value is negative,
* then one of the following values may be returned:
*
* -EINVAL invalid arguments or mm or virtual address are in an
* invalid vma (for instance device file vma).
* -ENOMEM: Out of memory.
* -EPERM: Invalid permission (for instance asking for write and
* range is read only).
* -EAGAIN: If you need to retry and mmap_sem was drop. This can only
* happens if block argument is false.
* -EBUSY: If the the range is being invalidated and you should wait
* for invalidation to finish.
* -EFAULT: Invalid (ie either no valid vma or it is illegal to access
* that range), number of valid pages in range->pfns[] (from
* range start address).
*
* This is similar to a regular CPU page fault except that it will not trigger
* any memory migration if the memory being faulted is not accessible by CPUs
* and caller does not ask for migration.
*
* On error, for one virtual address in the range, the function will mark the
* corresponding HMM pfn entry with an error flag.
*/
long hmm_range_fault(struct hmm_range *range, bool block)
{
const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
unsigned long start = range->start, end;
struct hmm_vma_walk hmm_vma_walk;
struct hmm *hmm = range->hmm;
struct vm_area_struct *vma;
struct mm_walk mm_walk;
int ret;
lockdep_assert_held(&hmm->mm->mmap_sem);
do {
/* If range is no longer valid force retry. */
if (!range->valid)
return -EBUSY;
vma = find_vma(hmm->mm, start);
if (vma == NULL || (vma->vm_flags & device_vma))
return -EFAULT;
if (is_vm_hugetlb_page(vma)) {
if (huge_page_shift(hstate_vma(vma)) !=
range->page_shift &&
range->page_shift != PAGE_SHIFT)
return -EINVAL;
} else {
if (range->page_shift != PAGE_SHIFT)
return -EINVAL;
}
if (!(vma->vm_flags & VM_READ)) {
/*
* If vma do not allow read access, then assume that it
* does not allow write access, either. HMM does not
* support architecture that allow write without read.
*/
hmm_pfns_clear(range, range->pfns,
range->start, range->end);
return -EPERM;
}
range->vma = vma;
hmm_vma_walk.pgmap = NULL;
hmm_vma_walk.last = start;
hmm_vma_walk.fault = true;
hmm_vma_walk.block = block;
hmm_vma_walk.range = range;
mm_walk.private = &hmm_vma_walk;
end = min(range->end, vma->vm_end);
mm_walk.vma = vma;
mm_walk.mm = vma->vm_mm;
mm_walk.pte_entry = NULL;
mm_walk.test_walk = NULL;
mm_walk.hugetlb_entry = NULL;
mm_walk.pud_entry = hmm_vma_walk_pud;
mm_walk.pmd_entry = hmm_vma_walk_pmd;
mm_walk.pte_hole = hmm_vma_walk_hole;
mm_walk.hugetlb_entry = hmm_vma_walk_hugetlb_entry;
do {
ret = walk_page_range(start, end, &mm_walk);
start = hmm_vma_walk.last;
/* Keep trying while the range is valid. */
} while (ret == -EBUSY && range->valid);
if (ret) {
unsigned long i;
i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
hmm_pfns_clear(range, &range->pfns[i],
hmm_vma_walk.last, range->end);
return ret;
}
start = end;
} while (start < range->end);
return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
}
EXPORT_SYMBOL(hmm_range_fault);
/**
* hmm_range_dma_map() - hmm_range_fault() and dma map page all in one.
* @range: range being faulted
* @device: device against to dma map page to
* @daddrs: dma address of mapped pages
* @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
* Return: number of pages mapped on success, -EAGAIN if mmap_sem have been
* drop and you need to try again, some other error value otherwise
*
* Note same usage pattern as hmm_range_fault().
*/
long hmm_range_dma_map(struct hmm_range *range,
struct device *device,
dma_addr_t *daddrs,
bool block)
{
unsigned long i, npages, mapped;
long ret;
ret = hmm_range_fault(range, block);
if (ret <= 0)
return ret ? ret : -EBUSY;
npages = (range->end - range->start) >> PAGE_SHIFT;
for (i = 0, mapped = 0; i < npages; ++i) {
enum dma_data_direction dir = DMA_TO_DEVICE;
struct page *page;
/*
* FIXME need to update DMA API to provide invalid DMA address
* value instead of a function to test dma address value. This
* would remove lot of dumb code duplicated accross many arch.
*
* For now setting it to 0 here is good enough as the pfns[]
* value is what is use to check what is valid and what isn't.
*/
daddrs[i] = 0;
page = hmm_device_entry_to_page(range, range->pfns[i]);
if (page == NULL)
continue;
/* Check if range is being invalidated */
if (!range->valid) {
ret = -EBUSY;
goto unmap;
}
/* If it is read and write than map bi-directional. */
if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
dir = DMA_BIDIRECTIONAL;
daddrs[i] = dma_map_page(device, page, 0, PAGE_SIZE, dir);
if (dma_mapping_error(device, daddrs[i])) {
ret = -EFAULT;
goto unmap;
}
mapped++;
}
return mapped;
unmap:
for (npages = i, i = 0; (i < npages) && mapped; ++i) {
enum dma_data_direction dir = DMA_TO_DEVICE;
struct page *page;
page = hmm_device_entry_to_page(range, range->pfns[i]);
if (page == NULL)
continue;
if (dma_mapping_error(device, daddrs[i]))
continue;
/* If it is read and write than map bi-directional. */
if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
dir = DMA_BIDIRECTIONAL;
dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
mapped--;
}
return ret;
}
EXPORT_SYMBOL(hmm_range_dma_map);
/**
* hmm_range_dma_unmap() - unmap range of that was map with hmm_range_dma_map()
* @range: range being unmapped
* @vma: the vma against which the range (optional)
* @device: device against which dma map was done
* @daddrs: dma address of mapped pages
* @dirty: dirty page if it had the write flag set
* Return: number of page unmapped on success, -EINVAL otherwise
*
* Note that caller MUST abide by mmu notifier or use HMM mirror and abide
* to the sync_cpu_device_pagetables() callback so that it is safe here to
* call set_page_dirty(). Caller must also take appropriate locks to avoid
* concurrent mmu notifier or sync_cpu_device_pagetables() to make progress.
*/
long hmm_range_dma_unmap(struct hmm_range *range,
struct vm_area_struct *vma,
struct device *device,
dma_addr_t *daddrs,
bool dirty)
{
unsigned long i, npages;
long cpages = 0;
/* Sanity check. */
if (range->end <= range->start)
return -EINVAL;
if (!daddrs)
return -EINVAL;
if (!range->pfns)
return -EINVAL;
npages = (range->end - range->start) >> PAGE_SHIFT;
for (i = 0; i < npages; ++i) {
enum dma_data_direction dir = DMA_TO_DEVICE;
struct page *page;
page = hmm_device_entry_to_page(range, range->pfns[i]);
if (page == NULL)
continue;
/* If it is read and write than map bi-directional. */
if (range->pfns[i] & range->flags[HMM_PFN_WRITE]) {
dir = DMA_BIDIRECTIONAL;
/*
* See comments in function description on why it is
* safe here to call set_page_dirty()
*/
if (dirty)
set_page_dirty(page);
}
/* Unmap and clear pfns/dma address */
dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
range->pfns[i] = range->values[HMM_PFN_NONE];
/* FIXME see comments in hmm_vma_dma_map() */
daddrs[i] = 0;
cpages++;
}
return cpages;
}
EXPORT_SYMBOL(hmm_range_dma_unmap);