netdev - Re: [PATCH net-next v2 1/3] xsk: Remove non-zero 'dma_page' check in xp_assign

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Message-ID: <75b6f7686c03519a1aaeb461618070747890143b.camel@redhat.com>
Date: Thu, 29 Feb 2024 11:43:10 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Yunjian Wang <wangyunjian@...wei.com>, mst@...hat.com, 
	willemdebruijn.kernel@...il.com, jasowang@...hat.com, kuba@...nel.org, 
	bjorn@...nel.org, magnus.karlsson@...el.com, maciej.fijalkowski@...el.com, 
	jonathan.lemon@...il.com, davem@...emloft.net
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org,  kvm@...r.kernel.org,
 virtualization@...ts.linux.dev, xudingke@...wei.com,  liwei395@...wei.com
Subject: Re: [PATCH net-next v2 1/3] xsk: Remove non-zero 'dma_page' check
 in xp_assign_dev

On Wed, 2024-02-28 at 19:05 +0800, Yunjian Wang 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.
> 
> 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 ce60ecd48a4d..a5af75b1f43c 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;
> -	}

This would unconditionally remove an otherwise valid check for most
NIC. What about let the driver declare it wont need DMA map with a
(pool?) flag.

Cheers,

Paolo