linux-kernel - Re: [PATCH v2 3/4] iommufd: Require DMABUF revoke semantics

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Message-ID: <20260119182300.GO13201@unreal>
Date: Mon, 19 Jan 2026 20:23:00 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Jason Gunthorpe <jgg@...pe.ca>
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>,
	Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Alex Williamson <alex@...zbot.org>, 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 v2 3/4] iommufd: Require DMABUF revoke semantics

On Mon, Jan 19, 2026 at 12:59:51PM -0400, Jason Gunthorpe wrote:
> On Sun, Jan 18, 2026 at 02:08:47PM +0200, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...dia.com>
> > 
> > IOMMUFD does not support page fault handling, and after a call to
> > .invalidate_mappings() all mappings become invalid. Ensure that
> > the IOMMUFD DMABUF importer is bound to a revoke‑aware DMABUF exporter
> > (for example, VFIO).
> > 
> > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > ---
> >  drivers/iommu/iommufd/pages.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/iommufd/pages.c b/drivers/iommu/iommufd/pages.c
> > index 76f900fa1687..a5eb2bc4ef48 100644
> > --- a/drivers/iommu/iommufd/pages.c
> > +++ b/drivers/iommu/iommufd/pages.c
> > @@ -1501,16 +1501,22 @@ static int iopt_map_dmabuf(struct iommufd_ctx *ictx, struct iopt_pages *pages,
> >  		mutex_unlock(&pages->mutex);
> >  	}
> >  
> > -	rc = sym_vfio_pci_dma_buf_iommufd_map(attach, &pages->dmabuf.phys);
> > +	rc = dma_buf_pin(attach);
> >  	if (rc)
> >  		goto err_detach;
> >  
> > +	rc = sym_vfio_pci_dma_buf_iommufd_map(attach, &pages->dmabuf.phys);
> > +	if (rc)
> > +		goto err_unpin;
> > +
> >  	dma_resv_unlock(dmabuf->resv);
> >  
> >  	/* On success iopt_release_pages() will detach and put the dmabuf. */
> >  	pages->dmabuf.attach = attach;
> >  	return 0;
> 
> Don't we need an explicit unpin after unmapping?

Yes, but this patch is going to be dropped in v3 because of this
suggestion.
https://lore.kernel.org/all/a397ff1e-615f-4873-98a9-940f9c16f85c@amd.com

Thanks


> 
> Jason