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/[email protected]/ So with vfio-pci and mlx5 both in-tree dmabuf users, implementing and consuming the callback, does this not satisfy the requirement? The userspace-driven semantics are inherent to VFIO's design. I don't see what additional value open sourcing the user-side provides for the kernel-side review process.
