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Date: Thu, 16 Apr 2026 18:02:11 +0300
From: Leon Romanovsky <leon@kernel.org>
To: Keith Busch <kbusch@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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In-Reply-To: <ad56liSM4zI2SWWp@kbusch-mbp>

On Tue, Apr 14, 2026 at 11:34:14AM -0600, Keith Busch wrote:
> On Thu, Apr 09, 2026 at 03:04:15PM +0300, Leon Romanovsky wrote:
> > Something like that, on top of this proposal:
> 
> ...
>   
> > +struct vfio_region_dma_tph {
> > +	u16 tag;
> > +	u8 ph;
> > +};
> > +
> >  struct vfio_region_dma_range {
> > -	__u64 offset;
> > -	__u64 length;
> > +	union {
> > +		__u64 offset;
> > +		struct vfio_region_dma_tph tph;
> > +	};
> > +	union {
> > +		__u64 length;
> > +		__u64 reserved;
> > +	};
> > +};
> > +
> > +enum {
> > +	VFIO_DMABUF_FLAG_TPH = 1 << 0,
> >  };
> 
> Okay, so you have the hints as a separate action from the dmabuf
> creation. 

I'm not sure I fully understood your point, but in my proposal the entire
operation is done in one pass, with the hints provided as the final entry in
the dma_range array.

Thanks