linux-kernel - Re: [PATCH v6 00/11] vfio/pci: Allow MMIO regions to be exported through dma-buf

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Message-ID: <aQpRz74RurfhZK15@Asurada-Nvidia>
Date: Tue, 4 Nov 2025 11:19:43 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Leon Romanovsky <leon@...nel.org>
CC: Bjorn Helgaas <bhelgaas@...gle.com>, Logan Gunthorpe
	<logang@...tatee.com>, Jens Axboe <axboe@...nel.dk>, Robin Murphy
	<robin.murphy@....com>, Joerg Roedel <joro@...tes.org>, Will Deacon
	<will@...nel.org>, Marek Szyprowski <m.szyprowski@...sung.com>, "Jason
 Gunthorpe" <jgg@...pe.ca>, Andrew Morton <akpm@...ux-foundation.org>,
	"Jonathan Corbet" <corbet@....net>, Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>, Alex
 Williamson <alex.williamson@...hat.com>, Kees Cook <kees@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>, Ankit Agrawal
	<ankita@...dia.com>, "Yishai Hadas" <yishaih@...dia.com>, Shameer Kolothum
	<skolothumtho@...dia.com>, "Kevin Tian" <kevin.tian@...el.com>, Krishnakant
 Jaju <kjaju@...dia.com>, Matt Ochs <mochs@...dia.com>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-block@...r.kernel.org>, <iommu@...ts.linux.dev>, <linux-mm@...ck.org>,
	<linux-doc@...r.kernel.org>, <linux-media@...r.kernel.org>,
	<dri-devel@...ts.freedesktop.org>, <linaro-mm-sig@...ts.linaro.org>,
	<kvm@...r.kernel.org>, <linux-hardening@...r.kernel.org>, Vivek Kasireddy
	<vivek.kasireddy@...el.com>
Subject: Re: [PATCH v6 00/11] vfio/pci: Allow MMIO regions to be exported
 through dma-buf

On Sun, Nov 02, 2025 at 10:00:48AM +0200, Leon Romanovsky wrote:
> Changelog:
> v6:
>  * Fixed wrong error check from pcim_p2pdma_init().
>  * Documented pcim_p2pdma_provider() function.
>  * Improved commit messages.
>  * Added VFIO DMA-BUF selftest.
>  * Added __counted_by(nr_ranges) annotation to struct vfio_device_feature_dma_buf.
>  * Fixed error unwind when dma_buf_fd() fails.
>  * Document latest changes to p2pmem.
>  * Removed EXPORT_SYMBOL_GPL from pci_p2pdma_map_type.
>  * Moved DMA mapping logic to DMA-BUF.
>  * Removed types patch to avoid dependencies between subsystems.
>  * Moved vfio_pci_dma_buf_move() in err_undo block.
>  * Added nvgrace patch.

I have verified this v6 using Jason's iommufd dmabuf branch:
https://github.com/jgunthorpe/linux/commits/iommufd_dmabuf/

by drafting a QEMU patch on top of Shameer's vSMMU v5 series:
https://github.com/nicolinc/qemu/commits/wip/iommufd_dmabuf/

with that, I see GPU BAR memory be correctly fetched in the QEMU:
vfio_region_dmabuf Device 0009:01:00.0, region "0009:01:00.0 BAR 0", offset: 0x0, size: 0x1000000
vfio_region_dmabuf Device 0009:01:00.0, region "0009:01:00.0 BAR 2", offset: 0x0, size: 0x44f00000
vfio_region_dmabuf Device 0009:01:00.0, region "0009:01:00.0 BAR 4", offset: 0x0, size: 0x17a0000000

Tested-by: Nicolin Chen <nicolinc@...dia.com>