linux-kernel - RE: [PATCH net-next 1/2] xsk: Remove non-zero 'dma_page' check in xp_assign

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Date: Wed, 21 Feb 2024 11:37:22 +0000
From: wangyunjian <wangyunjian@...wei.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "virtualization@...ts.linux.dev"
	<virtualization@...ts.linux.dev>, xudingke <xudingke@...wei.com>,
	"mst@...hat.com" <mst@...hat.com>, "willemdebruijn.kernel@...il.com"
	<willemdebruijn.kernel@...il.com>, "jasowang@...hat.com"
	<jasowang@...hat.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"davem@...emloft.net" <davem@...emloft.net>, "magnus.karlsson@...el.com"
	<magnus.karlsson@...el.com>
Subject: RE: [PATCH net-next 1/2] xsk: Remove non-zero 'dma_page' check in
 xp_assign_dev

> -----Original Message-----
> From: Xuan Zhuo [mailto:xuanzhuo@...ux.alibaba.com]
> Sent: Wednesday, February 21, 2024 5:53 PM
> To: wangyunjian <wangyunjian@...wei.com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> kvm@...r.kernel.org; virtualization@...ts.linux.dev; xudingke
> <xudingke@...wei.com>; wangyunjian <wangyunjian@...wei.com>;
> mst@...hat.com; willemdebruijn.kernel@...il.com; jasowang@...hat.com;
> kuba@...nel.org; davem@...emloft.net; magnus.karlsson@...el.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@...wei.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.

Thanks

> 
> Thanks.
> 
> 
> >
> > Signed-off-by: Yunjian Wang <wangyunjian@...wei.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
> >
> >