linux-kernel - Re: [PATCH v3 5/7] iommufd: Pin dma-buf importer for revoke semantics

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Message-ID: <916dda3b-583f-42fb-bbaa-bcb664e6825e@amd.com>
Date: Wed, 21 Jan 2026 10:01:34 +0100
From: Christian König <christian.koenig@....com>
To: 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>, Alex Williamson <alex@...zbot.org>,
 Ankit Agrawal <ankita@...dia.com>,
 Vivek Kasireddy <vivek.kasireddy@...el.com>
Cc: 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 v3 5/7] iommufd: Pin dma-buf importer for revoke semantics

On 1/20/26 15:07, 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 dma-buf importer is bound to a revoke‑aware dma-buf
> exporter (for example, VFIO).
> 
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>

I don't know the code well enough for a review, but that looks totally reasonable to me.

Acked-by: Christian König <christian.koenig@....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;
>  
> +err_unpin:
> +	dma_buf_unpin(attach);
>  err_detach:
>  	dma_resv_unlock(dmabuf->resv);
>  	dma_buf_detach(dmabuf, attach);
> @@ -1656,6 +1662,7 @@ void iopt_release_pages(struct kref *kref)
>  	if (iopt_is_dmabuf(pages) && pages->dmabuf.attach) {
>  		struct dma_buf *dmabuf = pages->dmabuf.attach->dmabuf;
>  
> +		dma_buf_unpin(pages->dmabuf.attach);
>  		dma_buf_detach(dmabuf, pages->dmabuf.attach);
>  		dma_buf_put(dmabuf);
>  		WARN_ON(!list_empty(&pages->dmabuf.tracker));
>