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

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Message-ID: <20260204165507.GH2328995@ziepe.ca>
Date: Wed, 4 Feb 2026 12:55:07 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
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>,
	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>,
	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, Feb 04, 2026 at 05:21:45PM +0100, Christian König 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.

Yes. It looks like Alex took it to his next tree:

commit 61ceaf236115f20f4fdd7cf60f883ada1063349a
Author: Leon Romanovsky <leon@...nel.org>
Date:   Wed Jan 21 17:45:02 2026 +0200

    vfio: Prevent from pinned DMABUF importers to attach to VFIO DMABUF
    
    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>
    Reviewed-by: Pranjal Shrivastava <praan@...gle.com>
    Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
    Link: https://lore.kernel.org/r/20260121-vfio-add-pin-v1-1-4e04916b17f1@nvidia.com
    Signed-off-by: Alex Williamson <alex@...zbot.org>

The very best thing would be to pull
61ceaf236115f20f4fdd7cf60f883ada1063349a which is cleanly based on
v6.19-rc6 ?

> 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.

Or we get Alex to take a branch from you for the first 3 and push it?

Jason