Commit e8569dd2 authored by Andreas Sandberg's avatar Andreas Sandberg Committed by Linus Torvalds
Browse files

mm/hugetlb.c: call MMU notifiers when copying a hugetlb page range

When copy_hugetlb_page_range() is called to copy a range of hugetlb
mappings, the secondary MMUs are not notified if there is a protection
downgrade, which breaks COW semantics in KVM.

This patch adds the necessary MMU notifier calls.
Signed-off-by: default avatarAndreas Sandberg <>
Acked-by: default avatarSteve Capper <>
Acked-by: default avatarMarc Zyngier <>
Cc: Mel Gorman <>
Cc: Rik van Riel <>
Cc: Hugh Dickins <>
Cc: Andrea Arcangeli <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 549543df
......@@ -2346,17 +2346,27 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
int cow;
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
int ret = 0;
cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
mmun_start = vma->vm_start;
mmun_end = vma->vm_end;
if (cow)
mmu_notifier_invalidate_range_start(src, mmun_start, mmun_end);
for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
spinlock_t *src_ptl, *dst_ptl;
src_pte = huge_pte_offset(src, addr);
if (!src_pte)
dst_pte = huge_pte_alloc(dst, addr, sz);
if (!dst_pte)
goto nomem;
if (!dst_pte) {
ret = -ENOMEM;
/* If the pagetables are shared don't copy or take references */
if (dst_pte == src_pte)
......@@ -2377,10 +2387,11 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
return 0;
return -ENOMEM;
if (cow)
mmu_notifier_invalidate_range_end(src, mmun_start, mmun_end);
return ret;
static int is_hugetlb_entry_migration(pte_t pte)
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