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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
Date: Tue, 31 Mar 2026 16:29:42 +0300	[thread overview]
Message-ID: <20260331132942.GC814676@unreal> (raw)
In-Reply-To: <acvFV8c5QVxnt3Em@kbusch-mbp>

On Tue, Mar 31, 2026 at 07:00:07AM -0600, Keith Busch wrote:
> On Tue, Mar 31, 2026 at 11:37:58AM +0300, Leon Romanovsky wrote:
> > On Thu, Mar 26, 2026 at 04:41:11PM -0600, Keith Busch wrote:
> > > 
> > > You're suggesting that Ziping append the new fields to the end of this
> > > struct? I don't think we can modify the layout of a uapi.
> > 
> > He needs to add before flex array. This struct is submitted by the user
> > and kernel can easily calculate the position of that array.
> 
> No, you can't just do that. Existing applications would break when they
> compile against the updated kernel header. They don't know about this
> new "tph" supplied flag, but they'll all accidently use the new
> dma_ranges offset. 

So we need to always pass TPH flag and treat 0 as do-nothing-field.

Thanks

  reply	other threads:[~2026-03-31 13:29 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20260324234615.3731237-1-zhipingz@meta.com>
     [not found] ` <20260324234615.3731237-2-zhipingz@meta.com>
2026-03-25  8:25   ` [RFC v2 1/2] vfio: add callback to get tph info for dmabuf Leon Romanovsky
2026-03-26 22:41     ` Keith Busch
2026-03-26 22:55       ` Zhiping Zhang
2026-03-31  8:39         ` Leon Romanovsky
2026-03-31  8:37       ` Leon Romanovsky
2026-03-31 13:00         ` Keith Busch
2026-03-31 13:29           ` Leon Romanovsky [this message]
2026-03-31 13:35             ` Keith Busch
2026-03-31 14:03               ` Leon Romanovsky
2026-03-31 14:13                 ` Keith Busch
2026-03-31 19:02                   ` Leon Romanovsky
2026-03-31 19:44                     ` Keith Busch
2026-03-28  2:21   ` fengchengwen
2026-03-31  0:49     ` Zhiping Zhang

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