Re: [PATCH net-next v4 1/3] net: devmem: allow rx-buf-size > PAGE_SIZE per dmabuf binding

[Bobby Eshleman <bobbyeshleman@gmail.com>]

On Wed, Jul 08, 2026 at 12:50:07PM +0200, Paolo Abeni wrote:
> On 7/7/26 10:36 PM, Mina Almasry wrote:
> > On Wed, Jul 1, 2026 at 12:22 PM Bobby Eshleman <bobbyeshleman@gmail.com> wrote:
> >>
> >> From: Bobby Eshleman <bobbyeshleman@meta.com>
> >>
> >> Every devmem dmabuf binding today hands the page_pool PAGE_SIZE niovs.
> >> This caps a single RX descriptor at PAGE_SIZE, burning CPU on buffer
> >> churn for large flows.
> >>
> >> Add a bind-time netlink attribute, NETDEV_A_DMABUF_RX_BUF_SIZE, that
> >> lets userspace request a larger niov size. The value must be a power of
> >> two >= PAGE_SIZE.
> >>
> >> Measurements
> >> ------------
> 
> Checkpatch complains about this separator usage:
> 
> ERROR: Invalid commit separator - some tools may have problems applying this
> #15:
> ------------
> 
> Please replace or remove it in the next revision
> 
> >> @@ -90,16 +90,17 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
> >>         struct dmabuf_genpool_chunk_owner *owner;
> >>         unsigned long dma_addr;
> >>         struct net_iov *niov;
> >> -       ssize_t offset;
> >> -       ssize_t index;
> >> +       size_t offset;
> >> +       size_t index;
> >>
> > 
> > nit: I would keep this signed. Some of the most frustrating issues I
> > ran into is some of the underflowing and then passing a > check or
> > something. Although if the LLM is not complaining about this
> > particular case, there is probably no issue with it. I also notice a
> > lot of existing code that deals with indexes and offsets goes for
> > signed.
> 
> At very least the above change should go in a separate patch, as is
> quite unrelated from the rest.
> 
> /P
> 

Sounds good, I'll drop the type change.

Thanks,
Bobby