linux-kernel - Re: [PATCH vfio-rc] vfio: Prevent from pinned DMABUF importers to attach to VFIO DMABUF

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Message-ID: <20260123103407.1778a2ac@shazbot.org>
Date: Fri, 23 Jan 2026 10:34:07 -0700
From: Alex Williamson <alex@...zbot.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: Ankit Agrawal <ankita@...dia.com>, Jason Gunthorpe <jgg@...pe.ca>, Kevin
 Tian <kevin.tian@...el.com>, Vivek Kasireddy <vivek.kasireddy@...el.com>,
 kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH vfio-rc] vfio: Prevent from pinned DMABUF importers to
 attach to VFIO DMABUF

On Wed, 21 Jan 2026 17:45:02 +0200
Leon Romanovsky <leon@...nel.org> wrote:

> From: Leon Romanovsky <leonro@...dia.com>
> 
> Some pinned importers, such as non-ODP RDMA ones, cannot invalidate their
> mappings and therefore must be prevented from attaching to this exporter.
> 
> Fixes: 5d74781ebc86 ("vfio/pci: Add dma-buf export support for MMIO regions")
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
> This is an outcome of this discussion about revoke functionality.
> https://lore.kernel.org/all/20260121134712.GZ961572@ziepe.ca
> 
> Thanks
> ---
>  drivers/vfio/pci/vfio_pci_dmabuf.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)

Applied to vfio for-linus branch for v6.19.  Thanks,

Alex


> 
> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
> index d4d0f7d08c53..4be4a85005cb 100644
> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c
> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
> @@ -20,6 +20,16 @@ struct vfio_pci_dma_buf {
>  	u8 revoked : 1;
>  };
>  
> +static int vfio_pci_dma_buf_pin(struct dma_buf_attachment *attachment)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static void vfio_pci_dma_buf_unpin(struct dma_buf_attachment *attachment)
> +{
> +	/* Do nothing */
> +}
> +
>  static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
>  				   struct dma_buf_attachment *attachment)
>  {
> @@ -76,6 +86,8 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
>  }
>  
>  static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
> +	.pin = vfio_pci_dma_buf_pin,
> +	.unpin = vfio_pci_dma_buf_unpin,
>  	.attach = vfio_pci_dma_buf_attach,
>  	.map_dma_buf = vfio_pci_dma_buf_map,
>  	.unmap_dma_buf = vfio_pci_dma_buf_unmap,
> 
> ---
> base-commit: acf44a2361b8d6356b71a970ab016065b5123b0e
> change-id: 20260121-vfio-add-pin-2229148da56e
> 
> Best regards,
> --  
> Leon Romanovsky <leonro@...dia.com>
> 
>