linux-kernel - Re: [PATCH v7 7/8] vfio: Permit VFIO to work with pinned importers

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Message-ID: <fb9bf53a-7962-451a-bac2-c61eb52c7a0f@amd.com>
Date: Wed, 4 Feb 2026 17:21:45 +0100
From: Christian König <christian.koenig@....com>
To: Leon Romanovsky <leon@...nel.org>, Sumit Semwal
 <sumit.semwal@...aro.org>, Alex Deucher <alexander.deucher@....com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Gerd Hoffmann <kraxel@...hat.com>,
 Dmitry Osipenko <dmitry.osipenko@...labora.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Lucas De Marchi <lucas.demarchi@...el.com>,
 Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>, Jason Gunthorpe <jgg@...pe.ca>,
 Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Felix Kuehling <Felix.Kuehling@....com>, Alex Williamson <alex@...zbot.org>,
 Ankit Agrawal <ankita@...dia.com>,
 Vivek Kasireddy <vivek.kasireddy@...el.com>
Cc: linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
 amd-gfx@...ts.freedesktop.org, virtualization@...ts.linux.dev,
 intel-xe@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
 iommu@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v7 7/8] vfio: Permit VFIO to work with pinned importers

On 1/31/26 06:34, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> Till now VFIO has rejected pinned importers, largely to avoid being used
> with the RDMA pinned importer that cannot handle a move_notify() to revoke
> access.
> 
> Using dma_buf_attach_revocable() it can tell the difference between pinned
> importers that support the flow described in dma_buf_invalidate_mappings()
> and those that don't.
> 
> Thus permit compatible pinned importers.
> 
> This is one of two items IOMMUFD requires to remove its private interface
> to VFIO's dma-buf.
> 
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> Reviewed-by: Alex Williamson <alex@...zbot.org>
> Reviewed-by: Christian König <christian.koenig@....com>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  drivers/vfio/pci/vfio_pci_dmabuf.c | 15 +++------------
>  1 file changed, 3 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
> index 78d47e260f34..a5fb80e068ee 100644
> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c
> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
> @@ -22,16 +22,6 @@ 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 */
> -}
> -

This chunk here doesn't want to apply to drm-misc-next, my educated guess is that the patch adding those lines is missing in that tree.

How should we handle that? Patches 1-3 have already been pushed to drm-misc-next and I would rather like to push patches 4-6 through that branch as well.

I can request a backmerge from the drm-misc-next maintainers, but then we clearly don't get that upstream this week.

Regards,
Christian.

>  static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
>  				   struct dma_buf_attachment *attachment)
>  {
> @@ -43,6 +33,9 @@ static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
>  	if (priv->revoked)
>  		return -ENODEV;
>  
> +	if (!dma_buf_attach_revocable(attachment))
> +		return -EOPNOTSUPP;
> +
>  	return 0;
>  }
>  
> @@ -107,8 +100,6 @@ 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,
>