From: Jason Gunthorpe <jgg@ziepe.ca>
To: Alex Williamson <alex@shazbot.org>
Cc: Zhiping Zhang <zhipingz@meta.com>,
Stanislav Fomichev <sdf@meta.com>,
Keith Busch <kbusch@kernel.org>,
Leon Romanovsky <leon@kernel.org>,
Bjorn Helgaas <helgaas@kernel.org>,
linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org,
netdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
Yochai Cohen <yochai@nvidia.com>,
Yishai Hadas <yishaih@nvidia.com>
Subject: Re: [PATCH v1 1/2] vfio: add callback to get tph info for dma-buf
Date: Thu, 23 Apr 2026 19:46:26 -0300 [thread overview]
Message-ID: <20260423224626.GV3611611@ziepe.ca> (raw)
In-Reply-To: <20260423132016.4a25e074@shazbot.org>
On Thu, Apr 23, 2026 at 01:20:16PM -0600, Alex Williamson wrote:
> My suggestion would be that we leave VFIO_DEVICE_FEATURE_DMA_BUF
> unchanged and add a VFIO_DEVICE_FEATURE_DMA_BUF_TPH ioctl which takes
> the fd from VFIO_DEVICE_FEATURE_DMA_BUF, along with a steering tag and
> processing hint. It would fdget() the dmabuf fd, validate it's a
> dmabuf via f_ops, validate it's a vfio exported dmabuf via dmabuf->ops,
> find the matching vfio_pci_dma_buf via priv under memory_lock, and
> stuff the provided TPH values into the object. It would be left to the
> user to sequence setting the TPH values on the dmabuf before the dmabuf
> is consumed by the importer.
>
> Is that a more reasonable uAPI? Thanks,
Off hand I think it can work, with the proviso that if userspace uses
the dmabuf before setting the tph the importer may ignore it. I don't
think that is a problem in practice.
Jason
next prev parent reply other threads:[~2026-04-23 22:46 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-20 18:39 [PATCH v1 0/2] Retrieve TPH from dma-buf for PCIe P2P memory access Zhiping Zhang
2026-04-20 18:39 ` [PATCH v1 1/2] vfio: add callback to get tph info for dma-buf Zhiping Zhang
2026-04-22 15:23 ` Alex Williamson
2026-04-22 16:29 ` Jason Gunthorpe
2026-04-22 19:27 ` Alex Williamson
2026-04-23 14:28 ` Jason Gunthorpe
2026-04-23 19:20 ` Alex Williamson
2026-04-23 22:46 ` Jason Gunthorpe [this message]
2026-04-24 5:41 ` Zhiping Zhang
2026-04-27 13:37 ` Leon Romanovsky
2026-04-27 14:28 ` Zhiping Zhang
2026-04-27 18:35 ` Leon Romanovsky
2026-04-20 18:39 ` [PATCH v1 2/2] RDMA/mlx5: get tph for p2p access when registering dma-buf mr Zhiping Zhang
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