linux-kernel - Re: [PATCH v1 10/10] vfio/pci: Add dma-buf export support for MMIO regions

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Message-ID: <20250804152618.GU402218@unreal>
Date: Mon, 4 Aug 2025 18:26:18 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: Jason Gunthorpe <jgg@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Christian König <christian.koenig@....com>,
	Christoph Hellwig <hch@....de>, dri-devel@...ts.freedesktop.org,
	iommu@...ts.linux.dev, Jens Axboe <axboe@...nel.dk>,
	Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	linux-mm@...ck.org, linux-pci@...r.kernel.org,
	Logan Gunthorpe <logang@...tatee.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Will Deacon <will@...nel.org>
Subject: Re: [PATCH v1 10/10] vfio/pci: Add dma-buf export support for MMIO
 regions

On Mon, Aug 04, 2025 at 04:00:45PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> Add support for exporting PCI device MMIO regions through dma-buf,
> enabling safe sharing of non-struct page memory with controlled
> lifetime management. This allows RDMA and other subsystems to import
> dma-buf FDs and build them into memory regions for PCI P2P operations.
> 
> The implementation provides a revocable attachment mechanism using
> dma-buf move operations. MMIO regions are normally pinned as BARs
> don't change physical addresses, but access is revoked when the VFIO
> device is closed or a PCI reset is issued. This ensures kernel
> self-defense against potentially hostile userspace.
> 
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@...el.com>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  drivers/vfio/pci/Kconfig           |  20 ++
>  drivers/vfio/pci/Makefile          |   2 +
>  drivers/vfio/pci/vfio_pci_config.c |  22 +-
>  drivers/vfio/pci/vfio_pci_core.c   |  25 +-
>  drivers/vfio/pci/vfio_pci_dmabuf.c | 390 +++++++++++++++++++++++++++++
>  drivers/vfio/pci/vfio_pci_priv.h   |  23 ++
>  include/linux/dma-buf.h            |   1 +
>  include/linux/vfio_pci_core.h      |   3 +
>  include/uapi/linux/vfio.h          |  25 ++
>  9 files changed, 506 insertions(+), 5 deletions(-)
>  create mode 100644 drivers/vfio/pci/vfio_pci_dmabuf.c

<...>

> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index d58e329ac0e71..f14b413aae48d 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -483,6 +483,7 @@ struct dma_buf_attach_ops {
>   * @dev: device attached to the buffer.
>   * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
>   * @peer2peer: true if the importer can handle peer resources without pages.
> + * #state: DMA structure to provide support for physical addresses DMA interface

This is rebase error, there is no need in this hunk.

Thanks