Re: [PATCH net] xsk: respect the offsets when copying frags

[Bui Quang Minh]

On 4/23/25 17:10, Bui Quang Minh wrote:
> Add the missing offsets when copying frags in xdp_copy_frags_from_zc().
>
> Fixes: 560d958c6c68 ("xsk: add generic XSk &xdp_buff -> skb conversion")
> Signed-off-by: Bui Quang Minh <minhquangbui99@xxxxxxxxx>
> ---
>   net/core/xdp.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index f86eedad586a..a723dc301f94 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -697,7 +697,8 @@ static noinline bool xdp_copy_frags_from_zc(struct sk_buff *skb,
>   	nr_frags = xinfo->nr_frags;
>   
>   	for (u32 i = 0; i < nr_frags; i++) {
> -		u32 len = skb_frag_size(&xinfo->frags[i]);
> +		const skb_frag_t *frag = &xinfo->frags[i];
> +		u32 len = skb_frag_size(frag);
>   		u32 offset, truesize = len;
>   		netmem_ref netmem;
>   
> @@ -707,8 +708,8 @@ static noinline bool xdp_copy_frags_from_zc(struct sk_buff *skb,
>   			return false;
>   		}
>   
> -		memcpy(__netmem_address(netmem),
> -		       __netmem_address(xinfo->frags[i].netmem),
> +		memcpy(__netmem_address(netmem) + offset,
> +		       __netmem_address(frag->netmem) + skb_frag_off(frag),
>   		       LARGEST_ALIGN(len));
>   		__skb_fill_netmem_desc_noacc(sinfo, i, netmem, offset, len);
>   

I know it's very unlikely but do we need to 
kmap_local_page(skb_frag_page(frag) before using 
__netmem_address(frag->netmem) to make sure the frag's page is mapped? 
Or it is impossible that the frag's page to be highmem and unmapped? Thanks,
Quang Minh.