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

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Message-ID: <20260119165951.GI961572@ziepe.ca>
Date: Mon, 19 Jan 2026 12:59:51 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
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>,
	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 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?

Jason