linux-kernel - Re: [PATCH v5 7/8] vfio: Permit VFIO to work with pinned importers

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Message-ID: <20260129140420.50d323a3@shazbot.org>
Date: Thu, 29 Jan 2026 14:04:20 -0700
From: Alex Williamson <alex@...zbot.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 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>,
 Ankit Agrawal <ankita@...dia.com>,
 Vivek Kasireddy <vivek.kasireddy@...el.com>, 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 v5 7/8] vfio: Permit VFIO to work with pinned importers

On Sat, 24 Jan 2026 21:14:19 +0200
Leon Romanovsky <leon@...nel.org> 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.
> 
> 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 485515629fe4..3c8dc56e2238 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 */
> -}
> -
>  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,
> 

I'm not sure what the merge plan is for the remaining patches, but I'll
toss my ack in so that it can all go through Christian's tree if he
prefers.  Thanks

Reviewed-by: Alex Williamson <alex@...zbot.org>