summaryrefslogtreecommitdiffstats
path: root/mm/hmm.c
diff options
context:
space:
mode:
Diffstat (limited to 'mm/hmm.c')
-rw-r--r--mm/hmm.c599
1 files changed, 599 insertions, 0 deletions
diff --git a/mm/hmm.c b/mm/hmm.c
new file mode 100644
index 000000000..3850fb625
--- /dev/null
+++ b/mm/hmm.c
@@ -0,0 +1,599 @@
+// 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/pagewalk.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>
+
+#include "internal.h"
+
+struct hmm_vma_walk {
+ struct hmm_range *range;
+ unsigned long last;
+};
+
+enum {
+ HMM_NEED_FAULT = 1 << 0,
+ HMM_NEED_WRITE_FAULT = 1 << 1,
+ HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT,
+};
+
+static int hmm_pfns_fill(unsigned long addr, unsigned long end,
+ struct hmm_range *range, unsigned long cpu_flags)
+{
+ unsigned long i = (addr - range->start) >> PAGE_SHIFT;
+
+ for (; addr < end; addr += PAGE_SIZE, i++)
+ range->hmm_pfns[i] = cpu_flags;
+ return 0;
+}
+
+/*
+ * hmm_vma_fault() - fault in a range lacking valid pmd or pte(s)
+ * @addr: range virtual start address (inclusive)
+ * @end: range virtual end address (exclusive)
+ * @required_fault: HMM_NEED_* flags
+ * @walk: mm_walk structure
+ * Return: -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_fault(unsigned long addr, unsigned long end,
+ unsigned int required_fault, struct mm_walk *walk)
+{
+ struct hmm_vma_walk *hmm_vma_walk = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ unsigned int fault_flags = FAULT_FLAG_REMOTE;
+
+ WARN_ON_ONCE(!required_fault);
+ hmm_vma_walk->last = addr;
+
+ if (required_fault & HMM_NEED_WRITE_FAULT) {
+ if (!(vma->vm_flags & VM_WRITE))
+ return -EPERM;
+ fault_flags |= FAULT_FLAG_WRITE;
+ }
+
+ for (; addr < end; addr += PAGE_SIZE)
+ if (handle_mm_fault(vma, addr, fault_flags, NULL) &
+ VM_FAULT_ERROR)
+ return -EFAULT;
+ return -EBUSY;
+}
+
+static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
+ unsigned long pfn_req_flags,
+ unsigned long cpu_flags)
+{
+ struct hmm_range *range = hmm_vma_walk->range;
+
+ /*
+ * So we not only consider the individual per page request we also
+ * consider the default flags requested for the range. The API can
+ * be used 2 ways. The first one where the HMM user coalesces
+ * multiple page faults into one request and sets flags per pfn for
+ * those faults. The second one where the HMM user wants 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.
+ */
+ pfn_req_flags &= range->pfn_flags_mask;
+ pfn_req_flags |= range->default_flags;
+
+ /* We aren't ask to do anything ... */
+ if (!(pfn_req_flags & HMM_PFN_REQ_FAULT))
+ return 0;
+
+ /* Need to write fault ? */
+ if ((pfn_req_flags & HMM_PFN_REQ_WRITE) &&
+ !(cpu_flags & HMM_PFN_WRITE))
+ return HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT;
+
+ /* If CPU page table is not valid then we need to fault */
+ if (!(cpu_flags & HMM_PFN_VALID))
+ return HMM_NEED_FAULT;
+ return 0;
+}
+
+static unsigned int
+hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
+ const unsigned long hmm_pfns[], unsigned long npages,
+ unsigned long cpu_flags)
+{
+ struct hmm_range *range = hmm_vma_walk->range;
+ unsigned int required_fault = 0;
+ unsigned long i;
+
+ /*
+ * If the default flags do not request to fault pages, and the mask does
+ * not allow for individual pages to be faulted, then
+ * hmm_pte_need_fault() will always return 0.
+ */
+ if (!((range->default_flags | range->pfn_flags_mask) &
+ HMM_PFN_REQ_FAULT))
+ return 0;
+
+ for (i = 0; i < npages; ++i) {
+ required_fault |= hmm_pte_need_fault(hmm_vma_walk, hmm_pfns[i],
+ cpu_flags);
+ if (required_fault == HMM_NEED_ALL_BITS)
+ return required_fault;
+ }
+ return required_fault;
+}
+
+static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
+ __always_unused int depth, struct mm_walk *walk)
+{
+ struct hmm_vma_walk *hmm_vma_walk = walk->private;
+ struct hmm_range *range = hmm_vma_walk->range;
+ unsigned int required_fault;
+ unsigned long i, npages;
+ unsigned long *hmm_pfns;
+
+ i = (addr - range->start) >> PAGE_SHIFT;
+ npages = (end - addr) >> PAGE_SHIFT;
+ hmm_pfns = &range->hmm_pfns[i];
+ required_fault =
+ hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0);
+ if (!walk->vma) {
+ if (required_fault)
+ return -EFAULT;
+ return hmm_pfns_fill(addr, end, range, HMM_PFN_ERROR);
+ }
+ if (required_fault)
+ return hmm_vma_fault(addr, end, required_fault, walk);
+ return hmm_pfns_fill(addr, end, range, 0);
+}
+
+static inline unsigned long hmm_pfn_flags_order(unsigned long order)
+{
+ return order << HMM_PFN_ORDER_SHIFT;
+}
+
+static inline unsigned long pmd_to_hmm_pfn_flags(struct hmm_range *range,
+ pmd_t pmd)
+{
+ if (pmd_protnone(pmd))
+ return 0;
+ return (pmd_write(pmd) ? (HMM_PFN_VALID | HMM_PFN_WRITE) :
+ HMM_PFN_VALID) |
+ hmm_pfn_flags_order(PMD_SHIFT - PAGE_SHIFT);
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
+ unsigned long end, unsigned long hmm_pfns[],
+ pmd_t pmd)
+{
+ struct hmm_vma_walk *hmm_vma_walk = walk->private;
+ struct hmm_range *range = hmm_vma_walk->range;
+ unsigned long pfn, npages, i;
+ unsigned int required_fault;
+ unsigned long cpu_flags;
+
+ npages = (end - addr) >> PAGE_SHIFT;
+ cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
+ required_fault =
+ hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, cpu_flags);
+ if (required_fault)
+ return hmm_vma_fault(addr, end, required_fault, walk);
+
+ pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+ for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
+ hmm_pfns[i] = pfn | cpu_flags;
+ return 0;
+}
+#else /* CONFIG_TRANSPARENT_HUGEPAGE */
+/* stub to allow the code below to compile */
+int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
+ unsigned long end, unsigned long hmm_pfns[], pmd_t pmd);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+static inline unsigned long 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) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : 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,
+ unsigned long *hmm_pfn)
+{
+ struct hmm_vma_walk *hmm_vma_walk = walk->private;
+ struct hmm_range *range = hmm_vma_walk->range;
+ unsigned int required_fault;
+ unsigned long cpu_flags;
+ pte_t pte = *ptep;
+ uint64_t pfn_req_flags = *hmm_pfn;
+
+ if (pte_none_mostly(pte)) {
+ required_fault =
+ hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
+ if (required_fault)
+ goto fault;
+ *hmm_pfn = 0;
+ return 0;
+ }
+
+ if (!pte_present(pte)) {
+ swp_entry_t entry = pte_to_swp_entry(pte);
+
+ /*
+ * Don't fault in device private pages owned by the caller,
+ * just report the PFN.
+ */
+ if (is_device_private_entry(entry) &&
+ pfn_swap_entry_to_page(entry)->pgmap->owner ==
+ range->dev_private_owner) {
+ cpu_flags = HMM_PFN_VALID;
+ if (is_writable_device_private_entry(entry))
+ cpu_flags |= HMM_PFN_WRITE;
+ *hmm_pfn = swp_offset_pfn(entry) | cpu_flags;
+ return 0;
+ }
+
+ required_fault =
+ hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
+ if (!required_fault) {
+ *hmm_pfn = 0;
+ return 0;
+ }
+
+ if (!non_swap_entry(entry))
+ goto fault;
+
+ if (is_device_private_entry(entry))
+ goto fault;
+
+ if (is_device_exclusive_entry(entry))
+ goto fault;
+
+ if (is_migration_entry(entry)) {
+ pte_unmap(ptep);
+ hmm_vma_walk->last = addr;
+ migration_entry_wait(walk->mm, pmdp, addr);
+ return -EBUSY;
+ }
+
+ /* Report error for everything else */
+ pte_unmap(ptep);
+ return -EFAULT;
+ }
+
+ cpu_flags = pte_to_hmm_pfn_flags(range, pte);
+ required_fault =
+ hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
+ if (required_fault)
+ goto fault;
+
+ /*
+ * Bypass devmap pte such as DAX page when all pfn requested
+ * flags(pfn_req_flags) are fulfilled.
+ * Since each architecture defines a struct page for the zero page, just
+ * fall through and treat it like a normal page.
+ */
+ if (!vm_normal_page(walk->vma, addr, pte) &&
+ !pte_devmap(pte) &&
+ !is_zero_pfn(pte_pfn(pte))) {
+ if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
+ pte_unmap(ptep);
+ return -EFAULT;
+ }
+ *hmm_pfn = HMM_PFN_ERROR;
+ return 0;
+ }
+
+ *hmm_pfn = pte_pfn(pte) | cpu_flags;
+ return 0;
+
+fault:
+ pte_unmap(ptep);
+ /* Fault any virtual address we were asked to fault */
+ return hmm_vma_fault(addr, end, required_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;
+ unsigned long *hmm_pfns =
+ &range->hmm_pfns[(start - range->start) >> PAGE_SHIFT];
+ unsigned long npages = (end - start) >> PAGE_SHIFT;
+ unsigned long addr = start;
+ pte_t *ptep;
+ pmd_t pmd;
+
+again:
+ pmd = READ_ONCE(*pmdp);
+ if (pmd_none(pmd))
+ return hmm_vma_walk_hole(start, end, -1, walk);
+
+ if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
+ if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) {
+ hmm_vma_walk->last = addr;
+ pmd_migration_entry_wait(walk->mm, pmdp);
+ return -EBUSY;
+ }
+ return hmm_pfns_fill(start, end, range, 0);
+ }
+
+ if (!pmd_present(pmd)) {
+ if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
+ return -EFAULT;
+ return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
+ }
+
+ if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
+ /*
+ * No need to take pmd_lock here, even if some other thread
+ * is splitting the huge pmd we will get that event through
+ * mmu_notifier callback.
+ *
+ * So just read pmd value and check again it's 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;
+
+ return hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd);
+ }
+
+ /*
+ * We have handled all the valid cases 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)) {
+ if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
+ return -EFAULT;
+ return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
+ }
+
+ ptep = pte_offset_map(pmdp, addr);
+ for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) {
+ int r;
+
+ r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns);
+ if (r) {
+ /* hmm_vma_handle_pte() did pte_unmap() */
+ return r;
+ }
+ }
+ pte_unmap(ptep - 1);
+ return 0;
+}
+
+#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
+ defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
+static inline unsigned long pud_to_hmm_pfn_flags(struct hmm_range *range,
+ pud_t pud)
+{
+ if (!pud_present(pud))
+ return 0;
+ return (pud_write(pud) ? (HMM_PFN_VALID | HMM_PFN_WRITE) :
+ HMM_PFN_VALID) |
+ hmm_pfn_flags_order(PUD_SHIFT - PAGE_SHIFT);
+}
+
+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;
+ pud_t pud;
+ spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
+
+ if (!ptl)
+ return 0;
+
+ /* Normally we don't want to split the huge page */
+ walk->action = ACTION_CONTINUE;
+
+ pud = READ_ONCE(*pudp);
+ if (pud_none(pud)) {
+ spin_unlock(ptl);
+ return hmm_vma_walk_hole(start, end, -1, walk);
+ }
+
+ if (pud_huge(pud) && pud_devmap(pud)) {
+ unsigned long i, npages, pfn;
+ unsigned int required_fault;
+ unsigned long *hmm_pfns;
+ unsigned long cpu_flags;
+
+ if (!pud_present(pud)) {
+ spin_unlock(ptl);
+ return hmm_vma_walk_hole(start, end, -1, walk);
+ }
+
+ i = (addr - range->start) >> PAGE_SHIFT;
+ npages = (end - addr) >> PAGE_SHIFT;
+ hmm_pfns = &range->hmm_pfns[i];
+
+ cpu_flags = pud_to_hmm_pfn_flags(range, pud);
+ required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns,
+ npages, cpu_flags);
+ if (required_fault) {
+ spin_unlock(ptl);
+ return hmm_vma_fault(addr, end, required_fault, walk);
+ }
+
+ pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
+ for (i = 0; i < npages; ++i, ++pfn)
+ hmm_pfns[i] = pfn | cpu_flags;
+ goto out_unlock;
+ }
+
+ /* Ask for the PUD to be split */
+ walk->action = ACTION_SUBTREE;
+
+out_unlock:
+ spin_unlock(ptl);
+ return 0;
+}
+#else
+#define hmm_vma_walk_pud NULL
+#endif
+
+#ifdef CONFIG_HUGETLB_PAGE
+static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
+ unsigned long start, unsigned long end,
+ struct mm_walk *walk)
+{
+ unsigned long addr = start, i, 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;
+ unsigned int required_fault;
+ unsigned long pfn_req_flags;
+ unsigned long cpu_flags;
+ spinlock_t *ptl;
+ pte_t entry;
+
+ ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
+ entry = huge_ptep_get(pte);
+
+ i = (start - range->start) >> PAGE_SHIFT;
+ pfn_req_flags = range->hmm_pfns[i];
+ cpu_flags = pte_to_hmm_pfn_flags(range, entry) |
+ hmm_pfn_flags_order(huge_page_order(hstate_vma(vma)));
+ required_fault =
+ hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
+ if (required_fault) {
+ spin_unlock(ptl);
+ return hmm_vma_fault(addr, end, required_fault, walk);
+ }
+
+ pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
+ for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
+ range->hmm_pfns[i] = pfn | cpu_flags;
+
+ spin_unlock(ptl);
+ return 0;
+}
+#else
+#define hmm_vma_walk_hugetlb_entry NULL
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static int hmm_vma_walk_test(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;
+
+ if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) &&
+ vma->vm_flags & VM_READ)
+ return 0;
+
+ /*
+ * vma ranges that don't have struct page backing them or map I/O
+ * devices directly cannot be handled by hmm_range_fault().
+ *
+ * If the vma does not allow read access, then assume that it does not
+ * allow write access either. HMM does not support architectures that
+ * allow write without read.
+ *
+ * If a fault is requested for an unsupported range then it is a hard
+ * failure.
+ */
+ if (hmm_range_need_fault(hmm_vma_walk,
+ range->hmm_pfns +
+ ((start - range->start) >> PAGE_SHIFT),
+ (end - start) >> PAGE_SHIFT, 0))
+ return -EFAULT;
+
+ hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
+
+ /* Skip this vma and continue processing the next vma. */
+ return 1;
+}
+
+static const struct mm_walk_ops hmm_walk_ops = {
+ .pud_entry = hmm_vma_walk_pud,
+ .pmd_entry = hmm_vma_walk_pmd,
+ .pte_hole = hmm_vma_walk_hole,
+ .hugetlb_entry = hmm_vma_walk_hugetlb_entry,
+ .test_walk = hmm_vma_walk_test,
+};
+
+/**
+ * hmm_range_fault - try to fault some address in a virtual address range
+ * @range: argument structure
+ *
+ * Returns 0 on success or one of the following error codes:
+ *
+ * -EINVAL: Invalid arguments or mm or virtual address is in an invalid vma
+ * (e.g., device file vma).
+ * -ENOMEM: Out of memory.
+ * -EPERM: Invalid permission (e.g., asking for write and range is read
+ * only).
+ * -EBUSY: The range has been invalidated and the caller needs to wait for
+ * the invalidation to finish.
+ * -EFAULT: A page was requested to be valid and could not be made valid
+ * ie it has no backing VMA or it is illegal to access
+ *
+ * This is similar to get_user_pages(), except that it can read the page tables
+ * without mutating them (ie causing faults).
+ */
+int hmm_range_fault(struct hmm_range *range)
+{
+ struct hmm_vma_walk hmm_vma_walk = {
+ .range = range,
+ .last = range->start,
+ };
+ struct mm_struct *mm = range->notifier->mm;
+ int ret;
+
+ mmap_assert_locked(mm);
+
+ do {
+ /* If range is no longer valid force retry. */
+ if (mmu_interval_check_retry(range->notifier,
+ range->notifier_seq))
+ return -EBUSY;
+ ret = walk_page_range(mm, hmm_vma_walk.last, range->end,
+ &hmm_walk_ops, &hmm_vma_walk);
+ /*
+ * When -EBUSY is returned the loop restarts with
+ * hmm_vma_walk.last set to an address that has not been stored
+ * in pfns. All entries < last in the pfn array are set to their
+ * output, and all >= are still at their input values.
+ */
+ } while (ret == -EBUSY);
+ return ret;
+}
+EXPORT_SYMBOL(hmm_range_fault);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 22:58:19 +0000