Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers

Jason Gunthorpe
2024-05-07T17:56:47Z

On Tue, May 07, 2024 at 06:25:52PM +0100, Pavel Begunkov wrote:
> On 5/7/24 17:48, Jason Gunthorpe wrote:
> > On Tue, May 07, 2024 at 09:42:05AM -0700, Mina Almasry wrote:
> >
> > > 1. Align with devmem TCP to use udmabuf for your io_uring memory. I
> > > think in the past you said it's a uapi you don't link but in the face
> > > of this pushback you may want to reconsider.
> >
> > dmabuf does not force a uapi, you can acquire your pages however you
> > want and wrap them up in a dmabuf. No uapi at all.
> >
> > The point is that dmabuf already provides ops that do basically what
> > is needed here. We don't need ops calling ops just because dmabuf's
> > ops are not understsood or not perfect. Fixup dmabuf.
>
> Those ops, for example, are used to efficiently return used buffers
> back to the kernel, which is uapi, I don't see how dmabuf can be
> fixed up to cover it.

Sure, but that doesn't mean you can't use dma buf for the other parts
of the flow. The per-page lifetime is a different topic than the
refcounting and access of the entire bulk of memory.

Jason