Subject: Re: [PATCH net v2] xdp: update mem type when page pool is used for generic XDP

From: Maciej Fijalkowski <[email-masked]>
Date: Wed, 1 Oct 2025 21:06:13 +0200

On Wed, Oct 01, 2025 at 08:27:37AM -0700, Jakub Kicinski wrote:
> On Wed, 1 Oct 2025 16:42:29 +0200 Maciej Fijalkowski wrote:
> > Here we piggy back on sk_buff::pp_recycle setting as it implies underlying
> > memory is backed by page pool.
> 
> skb->pp_recycle means that if the pages of the skb came from a pp then
> the skb is holding a pp reference not a full page reference on those
> pages. It does not mean that all pages of an skb came from pp.
> In practice it may be equivalent, especially here. But I'm slightly
> worried that checking pp_recycle will lead to confusion..

Mmm ok - maybe that's safer and straight-forward?

diff --git a/net/core/dev.c b/net/core/dev.c
index 93a25d87b86b..7707a95ca8ed 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5269,6 +5269,9 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp,
 	orig_bcast = is_multicast_ether_addr_64bits(eth->h_dest);
 	orig_eth_type = eth->h_proto;
 
+	xdp->rxq->mem.type = page_pool_page_is_pp(virt_to_page(xdp->data)) ?
+		MEM_TYPE_PAGE_POOL : MEM_TYPE_PAGE_SHARED;
+
 	act = bpf_prog_run_xdp(xdp_prog, xdp);
 
 	/* check if bpf_xdp_adjust_head was used */

As you know we do not have that kind of granularity within xdp_buff where
we could distinguish the memory provider per linear part and each frag...