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: Andreas Sandberg <[email protected]> Acked-by: Steve Capper <[email protected]> Acked-by: Marc Zyngier <[email protected]> --- mm/hugetlb.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 0b7656e..f5c5002 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2372,16 +2372,26 @@ 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; + 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) { src_pte = huge_pte_offset(src, addr); if (!src_pte) continue; dst_pte = huge_pte_alloc(dst, addr, sz); - if (!dst_pte) - goto nomem; + if (!dst_pte) { + ret = -ENOMEM; + break; + } /* If the pagetables are shared don't copy or take references */ if (dst_pte == src_pte) @@ -2401,10 +2411,11 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, spin_unlock(&src->page_table_lock); spin_unlock(&dst->page_table_lock); } - return 0; -nomem: - 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) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
