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    Subject[PATCH v4.9.y 1/3] vfio/type1: Support faulting PFNMAP vmas
    Date
    From: Alex Williamson <alex.williamson@redhat.com>

    commit 41311242221e3482b20bfed10fa4d9db98d87016 upstream.

    With conversion to follow_pfn(), DMA mapping a PFNMAP range depends on
    the range being faulted into the vma. Add support to manually provide
    that, in the same way as done on KVM with hva_to_pfn_remapped().

    Reviewed-by: Peter Xu <peterx@redhat.com>
    Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
    [Ajay: Regenerated the patch for v4.9]
    Signed-off-by: Ajay Kaher <akaher@vmware.com>
    ---
    drivers/vfio/vfio_iommu_type1.c | 36 +++++++++++++++++++++++++++++++++---
    1 file changed, 33 insertions(+), 3 deletions(-)

    diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
    index a9f58f3..ccef02c 100644
    --- a/drivers/vfio/vfio_iommu_type1.c
    +++ b/drivers/vfio/vfio_iommu_type1.c
    @@ -213,6 +213,32 @@ static int put_pfn(unsigned long pfn, int prot)
    return 0;
    }

    +static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
    + unsigned long vaddr, unsigned long *pfn,
    + bool write_fault)
    +{
    + int ret;
    +
    + ret = follow_pfn(vma, vaddr, pfn);
    + if (ret) {
    + bool unlocked = false;
    +
    + ret = fixup_user_fault(NULL, mm, vaddr,
    + FAULT_FLAG_REMOTE |
    + (write_fault ? FAULT_FLAG_WRITE : 0),
    + &unlocked);
    + if (unlocked)
    + return -EAGAIN;
    +
    + if (ret)
    + return ret;
    +
    + ret = follow_pfn(vma, vaddr, pfn);
    + }
    +
    + return ret;
    +}
    +
    static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)
    {
    struct page *page[1];
    @@ -226,12 +252,16 @@ static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)

    down_read(&current->mm->mmap_sem);

    +retry:
    vma = find_vma_intersection(current->mm, vaddr, vaddr + 1);

    if (vma && vma->vm_flags & VM_PFNMAP) {
    - if (!follow_pfn(vma, vaddr, pfn) &&
    - is_invalid_reserved_pfn(*pfn))
    - ret = 0;
    + ret = follow_fault_pfn(vma, current->mm, vaddr, pfn, prot & IOMMU_WRITE);
    + if (ret == -EAGAIN)
    + goto retry;
    +
    + if (!ret && !is_invalid_reserved_pfn(*pfn))
    + ret = -EFAULT;
    }

    up_read(&current->mm->mmap_sem);
    --
    2.7.4
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