Re: [PATCH net-next 3/4] selftests/net: ncdevmem: add -b option to set rx-buf-size on bind

[Bobby Eshleman <bobbyeshleman@gmail.com>]

On Fri, Jun 05, 2026 at 08:35:25AM -0700, Stanislav Fomichev wrote:
> On 06/03, Bobby Eshleman wrote:
> > From: Bobby Eshleman <bobbyeshleman@meta.com>
> > 
> > Add -b <bytes> to request a non-default niov size via
> > NETDEV_A_DMABUF_RX_BUF_SIZE. When the value exceeds PAGE_SIZE,
> > udmabuf_alloc() switches to an MFD_HUGETLB-backed memfd so each 2 MB
> > hugepage produces one naturally-aligned sg entry.
> > 
> > Reject values > 2 MB up front: MFD_HUGETLB + udmabuf can only guarantee
> > 2 MB per sg entry (one hugepage), so a larger rx_buf_size would fail the
> > per-sg length/alignment check.
> > 
> > Add CONFIG_HUGETLBFS=y to drivers/net/hw/config so the new path is
> > reachable in the CI kernels built for these tests.
> 
> I vaguely remember there was also some kernel cmdline argument to
> reserve these? Do we need to also do something to NIPA to reserve 2MB
> pages for this test? Or was it for 1GB pages?

Good call, my little runner script when prototyping this adds these
pages at runtime and I forgot to move it into the patch, we can have the
py runner do this setup.

Best,
Bobby