Re: [PATCH 4/7] vfio/platform: keep logical vm_pgoff in MMIO region mmap

[Alex Williamson <alex@shazbot.org>]

On Mon, 21 Sep 2026 15:23:31 +0300
Abdifatah Suruur <suruurism@gmail.com> wrote:

> vfio_platform_mmap_mmio() overwrites vma->vm_pgoff with the physical
> frame number of the MMIO region and passes it to remap_pfn_range().
> The VMA is inserted into the device file's mapping->i_mmap interval
> tree keyed by vm_pgoff, which VFIO expects to be the logical file
> offset: the core links every device mmap to the device inode's
> i_mapping precisely so that unmap_mapping_range() can revoke all
> mappings associated with a device (see vfio_device_cdev_open()).
> 
> With a raw PFN in vm_pgoff the interval tree entry lands in the wrong
> coordinate space and unmap_mapping_range() cannot find the VMA,
> leaving stale MMIO mappings behind any revocation attempt.  Keep
> vm_pgoff in the logical VFIO offset space, as vfio-pci does, and pass
> the physical PFN to remap_pfn_range() explicitly.
> 
> This is defensive hygiene: none of vfio-platform, vfio/fsl-mc and
> vfio/cdx call unmap_mapping_range() today, so no reachable
> stale-mapping issue exists.  Keeping vm_pgoff logical preserves the
> VFIO core contract for any future revocation path.
> 
> Signed-off-by: Abdifatah Suruur <suruurism@gmail.com>
> ---
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -561,6 +561,5 @@
>  	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> -	vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
> -
> -	return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
> +	return remap_pfn_range(vma, vma->vm_start,
> +			       (region.addr >> PAGE_SHIFT) + pgoff,
>  			       req_len, vma->vm_page_prot);
>  }

Eric had provided a Reviewed-by in [1], I think the only difference is
the commit log, including dropping the Fixes: tag since it's not
currently reachable.  I'd keep the R-b for that, or he can re-add it on
the next spin.  Thanks,

Alex

[1]https://lore.kernel.org/all/21fda51a-6974-487d-874a-387dd73e2346@redhat.com/