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

[Eric Auger]

On 9/29/26 1:00 AM, Alex Williamson wrote:
> On Mon, 21 Sep 2026 15:23:31 +0300
> Abdifatah Suruur <suruurism@xxxxxxxxx> 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@xxxxxxxxx>
>> ---
>> --- 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,
I do agree. Feel free to keep the R-b

Eric
>
> Alex
>
> [1]https://lore.kernel.org/all/21fda51a-6974-487d-874a-387dd73e2346@xxxxxxxxxx/
>