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Date: Tue, 31 Mar 2026 13:44:02 -0600
From: Keith Busch <kbusch@kernel.org>
To: Leon Romanovsky <leon@kernel.org>
Cc: Zhiping Zhang <zhipingz@meta.com>, Jason Gunthorpe <jgg@ziepe.ca>,
	Bjorn Helgaas <bhelgaas@google.com>, 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>,
	Bjorn Helgaas <helgaas@kernel.org>
Subject: Re: [RFC v2 1/2] vfio: add callback to get tph info for dmabuf
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References: <20260324234615.3731237-2-zhipingz@meta.com>
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 <acvNsvS5ShlQlrox@kbusch-mbp>
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In-Reply-To: <20260331190220.GI814676@unreal>

On Tue, Mar 31, 2026 at 10:02:20PM +0300, Leon Romanovsky wrote:
> 
> Right, what about adding TPH fields to struct vfio_region_dma_range
> instead of struct vfio_device_feature_dma_buf?

You might have to show me with code what you're talking about because I
can't see any way we can add fields to any struct here without breaking
backward compatibility.

If we can't claim bits out of the unused "flags" field for this feature,
then my initial reply is the only sane approach: we can introduce a new
feature and struct for it that closely mirrors the existing one, but
with the extra hint fields.