netdev - Re: [RFC 0/2] Retrieve tph from dmabuf for PCIe P2P memory access

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Message-ID: <20260209232826.3567769-1-zhipingz@meta.com>
Date: Mon, 9 Feb 2026 15:28:24 -0800
From: Zhiping Zhang <zhipingz@...a.com>
To: Jason Gunthorpe <jgg@...pe.ca>
CC: Leon Romanovsky <leon@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        <linux-rdma@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <netdev@...r.kernel.org>, Keith Busch <kbusch@...nel.org>,
        Yochai Cohen
	<yochai@...dia.com>, Yishai Hadas <yishaih@...dia.com>,
        Zhiping Zhang
	<zhipingz@...a.com>
Subject: Re: [RFC 0/2] Retrieve tph from dmabuf for PCIe P2P memory access

On Mon, Feb 08, 2026 at 10:13:00AM -0800, Jason Gunthor write:

> On Mon, Feb 09, 2026 at 09:53:10AM -0800, Zhiping Zhang wrote:
> > Currently, the steering tag can be used for a CPU on the motherboard; the
> > ACPI check is in place to query and obtain the supported tph settings. Here
> > we intend to use the tph info to improve RDMA NIC memory access on a vfio-based
> > accelerator device via PCIe peer-to-peer. When an applicantion register a
> > RDMA memory region with DMABUF for the RDMA NIC to access the device memory,
> > the tph associated with the memory region can be retrieved and used to set the
> > steering tag / process hint (ph). The tph contains additional instructions
> > or hints to the GPU or accelerator device for advanced memory operations,
> > such as, read cache selection.
> >
> > Note this RFC is for the discussion on the direction and is not intended to be
> > a complete implementation. Once the direction is agreed on, we will work on the
> > implementation or a real patch set.
>
> you didn't cc the DRM people who really need to look at any changes to
> the dmabuf contract.
>
> Jason

Thanks, let me submit again including the DRM people via the mailing list
dri-devel@...ts.freedesktop.org.

Zhiping