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From: wangyunjian <wangyunjian@huawei.com>
To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
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Subject: RE: [PATCH net-next 1/2] xsk: Remove non-zero 'dma_page' check in
 xp_assign_dev
Thread-Topic: [PATCH net-next 1/2] xsk: Remove non-zero 'dma_page' check in
 xp_assign_dev
Thread-Index: AQHaTqj5aHEEh4wXi06uw11VbniHk7EUM/IAgAChCpA=
Date: Wed, 21 Feb 2024 11:37:22 +0000
Message-ID: <0fce8b64808f4c6faa0eb60e44687c36@huawei.com>
References: <1706089058-1364-1-git-send-email-wangyunjian@huawei.com>
 <1708509152.9501102-1-xuanzhuo@linux.alibaba.com>
In-Reply-To: <1708509152.9501102-1-xuanzhuo@linux.alibaba.com>
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> -----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 i=
n
> xp_assign_dev
>=20
> 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.
>=20
> 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

>=20
> Thanks.
>=20
>=20
> >
> > 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 =3D -EINVAL;
> > -		goto err_unreg_xsk;
> > -	}
> >  	pool->umem->zc =3D true;
> >  	return 0;
> >
> > -err_unreg_xsk:
> > -	xp_disable_drv_zc(pool);
> >  err_unreg_pool:
> >  	if (!force_zc)
> >  		err =3D 0; /* fallback to copy mode */
> > --
> > 2.33.0
> >
> >