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

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Message-ID: <20260204095659.5a983af2@shazbot.org>
Date: Wed, 4 Feb 2026 09:56:59 -0700
From: Alex Williamson <alex@...zbot.org>
To: Christian König <christian.koenig@....com>
Cc: 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>,
 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 v7 7/8] vfio: Permit VFIO to work with pinned importers

On Wed, 4 Feb 2026 17:21:45 +0100
Christian König <christian.koenig@....com> wrote:

> 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.

Hmm, drm-next already has a backmerge up to v6.19-rc7, the patch here is
based on a commit merged in rc8.  The tag for that change was based on
rc6.  It can be found here:

https://github.com/awilliam/linux-vfio.git tags/vfio-v6.19-rc8

As the same tag Linus merged in:

1f97d9dcf536 ("Merge tag 'vfio-v6.19-rc8' of https://github.com/awilliam/linux-vfio")

drm-misc-next only seems to be based on v6.19-rc1 though, so I don't
know that any of that helps.  Thanks,

Alex

> >  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,
> >   
> 
>