vfio: Fix PCI mmap after b3b9c29

Our mmap path mistakely relied on vma->vm_pgoff to get set in
remap_pfn_range.  After b3b9c29, that path only applies to
copy-on-write mappings.  Set it in our own code.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/vfio_pci.c

@@ -408,7 +408,7 @@ static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
 	struct vfio_pci_device *vdev = device_data;
 	struct pci_dev *pdev = vdev->pdev;
 	unsigned int index;
-	u64 phys_len, req_len, pgoff, req_start, phys;
+	u64 phys_len, req_len, pgoff, req_start;
 	int ret;
 
 	index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
@@ -463,10 +463,9 @@ static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
 	vma->vm_private_data = vdev;
 	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vma->vm_pgoff = (pci_resource_start(pdev, index) >> PAGE_SHIFT) + pgoff;
 
-	phys = (pci_resource_start(pdev, index) >> PAGE_SHIFT) + pgoff;
-
-	return remap_pfn_range(vma, vma->vm_start, phys,
+	return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
 			       req_len, vma->vm_page_prot);
 }