Hi Cédric,
-----Original Message----- From: Cédric Le Goater clg@redhat.com Sent: 17 December 2025 17:02 To: Nicolin Chen nicolinc@nvidia.com; Leon Romanovsky leon@kernel.org Cc: Bjorn Helgaas bhelgaas@google.com; Logan Gunthorpe logang@deltatee.com; Jens Axboe axboe@kernel.dk; Robin Murphy robin.murphy@arm.com; Joerg Roedel joro@8bytes.org; Will Deacon will@kernel.org; Marek Szyprowski m.szyprowski@samsung.com; Jason Gunthorpe jgg@ziepe.ca; Andrew Morton akpm@linux-foundation.org; Jonathan Corbet corbet@lwn.net; Sumit Semwal sumit.semwal@linaro.org; Christian König christian.koenig@amd.com; Alex Williamson alex.williamson@redhat.com; Kees Cook kees@kernel.org; Gustavo A. R. Silva gustavoars@kernel.org; Ankit Agrawal ankita@nvidia.com; Yishai Hadas yishaih@nvidia.com; Shameer Kolothum skolothumtho@nvidia.com; Kevin Tian kevin.tian@intel.com; Krishnakant Jaju kjaju@nvidia.com; Matt Ochs mochs@nvidia.com; linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org; linux- block@vger.kernel.org; iommu@lists.linux.dev; linux-mm@kvack.org; linux- doc@vger.kernel.org; linux-media@vger.kernel.org; dri- devel@lists.freedesktop.org; linaro-mm-sig@lists.linaro.org; kvm@vger.kernel.org; linux-hardening@vger.kernel.org; Vivek Kasireddy vivek.kasireddy@intel.com Subject: Re: [PATCH v6 00/11] vfio/pci: Allow MMIO regions to be exported through dma-buf
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Hello Nicolin,
On 11/4/25 20:19, Nicolin Chen wrote:
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@nvidia.com
Do you plan to provide P2P support with IOMMUFD for QEMU ?
Yes. We do plan to send that support patch soon.
Thanks, Shameer