Re: RE: [PATCH net-next 1/2] xsk: Remove non-zero 'dma_page' check in xp_assign_dev

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Wed, 21 Feb 2024 11:37:22 +0000, wangyunjian <wangyunjian@huawei.com> wrote:
> > -----Original Message-----
> > From: Xuan Zhuo [mailto:xuanzhuo@linux.alibaba.com]
> > Sent: Wednesday, February 21, 2024 5:53 PM
> > To: wangyunjian <wangyunjian@huawei.com>
> > Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
> > kvm@vger.kernel.org; virtualization@lists.linux.dev; xudingke
> > <xudingke@huawei.com>; wangyunjian <wangyunjian@huawei.com>;
> > mst@redhat.com; willemdebruijn.kernel@gmail.com; jasowang@redhat.com;
> > kuba@kernel.org; davem@davemloft.net; magnus.karlsson@intel.com
> > Subject: Re: [PATCH net-next 1/2] xsk: Remove non-zero 'dma_page' check in
> > xp_assign_dev
> >
> > On Wed, 24 Jan 2024 17:37:38 +0800, Yunjian Wang
> > <wangyunjian@huawei.com> wrote:
> > > Now dma mappings are used by the physical NICs. However the vNIC maybe
> > > do not need them. So remove non-zero 'dma_page' check in
> > > xp_assign_dev.
> >
> > Could you tell me which one nic can work with AF_XDP without DMA?
>
> TUN will support AF_XDP Tx zero-copy, which does not require DMA mappings.


Great. Though I do not know how it works, but I think a new option or feature
is better.

Thanks.


>
> Thanks
>
> >
> > Thanks.
> >
> >
> > >
> > > Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> > > ---
> > >  net/xdp/xsk_buff_pool.c | 7 -------
> > >  1 file changed, 7 deletions(-)
> > >
> > > diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c index
> > > 28711cc44ced..939b6e7b59ff 100644
> > > --- a/net/xdp/xsk_buff_pool.c
> > > +++ b/net/xdp/xsk_buff_pool.c
> > > @@ -219,16 +219,9 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
> > >  	if (err)
> > >  		goto err_unreg_pool;
> > >
> > > -	if (!pool->dma_pages) {
> > > -		WARN(1, "Driver did not DMA map zero-copy buffers");
> > > -		err = -EINVAL;
> > > -		goto err_unreg_xsk;
> > > -	}
> > >  	pool->umem->zc = true;
> > >  	return 0;
> > >
> > > -err_unreg_xsk:
> > > -	xp_disable_drv_zc(pool);
> > >  err_unreg_pool:
> > >  	if (!force_zc)
> > >  		err = 0; /* fallback to copy mode */
> > > --
> > > 2.33.0
> > >
> > >