Re: [PATCH net v2] net: ethernet: ti: am65-cpsw-nuss: Fix skb size by accounting for skb_shared_info

[Jakub Kicinski]

On Thu, 26 Jun 2025 10:42:26 +0530 Chintan Vankar wrote:
> While transitioning from netdev_alloc_ip_align() to build_skb(), memory
> for the "skb_shared_info" member of an "skb" was not allocated. Fix this
> by including sizeof(skb_shared_info) in the packet length during
> allocation.
> 
> Fixes: 8acacc40f733 ("net: ethernet: ti: am65-cpsw: Add minimal XDP support")
> Signed-off-by: Chintan Vankar <c-vankar@xxxxxx>
> ---
> 
> This patch is based on the commit '9caca6ac0e26' of origin/main branch of
> Linux-net repository.
> 
> Link to v1:
> https://lore.kernel.org/r/598f9e77-8212-426b-97ab-427cb8bd4910@xxxxxx/
> 
> Changes from v1 to v2:
> - Updated commit message and code change as suggested by Siddharth
>   Vadapalli.
> 
>  drivers/net/ethernet/ti/am65-cpsw-nuss.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> index f20d1ff192ef..67fef2ea4900 100644
> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> @@ -856,7 +856,7 @@ static struct sk_buff *am65_cpsw_build_skb(void *page_addr,
>  {
>  	struct sk_buff *skb;
>  
> -	len += AM65_CPSW_HEADROOM;
> +	len += AM65_CPSW_HEADROOM + SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
>  
>  	skb = build_skb(page_addr, len);

Looks to me like each packet is placed in a full page, isn't it?
If that's the case the correct value for "buffer size" is PAGE_SIZE
-- 
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