Re: [PATCH v5 0/4] vfio/dma-buf: add TPH support for peer-to-peer access

[Jason Gunthorpe <jgg@ziepe.ca>]

On Fri, May 29, 2026 at 02:31:30PM -0600, Keith Busch wrote:
> On Fri, May 29, 2026 at 09:36:00AM +0200, Christian König wrote:
> > On 5/29/26 08:34, Zhiping Zhang wrote:
> > ...
> > > There's no in-tree vendor PF driver
> > 
> > Well I have to admit it's a bit on the edge but this sentence is a show stopper.
> > 
> > DMA-buf is an in kernel interface for buffer sharing between drivers and any change to it needs an in kernel driver as justification for the added complexity.
> > 
> > > - the device is a Meta MTIA
> > > accelerator managed entirely from userspace via VFIO passthrough.
> > 
> > When you have a complete open source driver stack which utilizes VFIO passthrough as the interface to communicate with the kernel drivers then we can eventually talk about that.
> > 
> > But as far as I can see without upstreaming or at least open sourcing the full stack to utilize this functionality it's a clear NAK to upstreaming this.
> 
> But the existing dmabuf for vfio-pci was accepted upstream without these
> requirements. I see you had concerns about even that, but still Acked
> under the same model that's propsed in this series:
> 
>   https://lore.kernel.org/linux-pci/57b8876f-1399-4e4d-a44b-1177787aa17d@amd.com/

To be fair that is quite different there isn't a proprietary userspace
issue for that series, and there should be more users of the API when
the GPU drivers migrate..

Jason