[PATCH RFC 09/10] vfio/type1: Use follow_pfn for VM_FPNMAP VMAs

[Joao Martins]

From: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>

Unconditionally interpreting vm_pgoff as a PFN is incorrect.

VMAs created by /dev/mem do this, but in general VM_PFNMAP just means
that the VMA doesn't have an associated struct page and is being managed
directly by something other than the core mmu.

Use follow_pfn like KVM does to find the PFN.

Signed-off-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 2ada8e6cdb88..1e43581f95ea 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -362,9 +362,9 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 	vma = find_vma_intersection(mm, vaddr, vaddr + 1);
 
 	if (vma && vma->vm_flags & VM_PFNMAP) {
-		*pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
-		if (is_invalid_reserved_pfn(*pfn))
-			ret = 0;
+		ret = follow_pfn(vma, vaddr, pfn);
+		if (!ret && !is_invalid_reserved_pfn(*pfn))
+			ret = -EOPNOTSUPP;
 	}
 
 	up_read(&mm->mmap_sem);
-- 
2.17.1