Re: [RFC PATCH v2 00/11] Device Memory TCP

[Jason Gunthorpe <jgg@ziepe.ca>]

On Thu, Aug 10, 2023 at 12:29:08PM +0200, Christian König wrote:
> Am 10.08.23 um 03:57 schrieb Mina Almasry:
> > Changes in RFC v2:
> > ------------------
> > 
> > The sticking point in RFC v1[1] was the dma-buf pages approach we used to
> > deliver the device memory to the TCP stack. RFC v2 is a proof-of-concept
> > that attempts to resolve this by implementing scatterlist support in the
> > networking stack, such that we can import the dma-buf scatterlist
> > directly.
> 
> Impressive work, I didn't thought that this would be possible that "easily".
> 
> Please note that we have considered replacing scatterlists with simple
> arrays of DMA-addresses in the DMA-buf framework to avoid people trying to
> access the struct page inside the scatterlist.
> 
> It might be a good idea to push for that first before this here is finally
> implemented.
> 
> GPU drivers already convert the scatterlist used to arrays of DMA-addresses
> as soon as they get them. This leaves RDMA and V4L as the other two main
> users which would need to be converted.

Oh that would be a nightmare for RDMA.

We need a standard based way to have scalable lists of DMA addresses :(

> > 2. Netlink API (Patch 1 & 2).
> 
> How does netlink manage the lifetime of objects?

And access control..

Jason