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

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Message-ID: <aN17pc5/ZBQednNi@boxer>
Date: Wed, 1 Oct 2025 21:06:13 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Octavian Purdila <tavip@...gle.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <pabeni@...hat.com>, <horms@...nel.org>,
	<ast@...nel.org>, <daniel@...earbox.net>, <hawk@...nel.org>,
	<john.fastabend@...il.com>, <sdf@...ichev.me>, <kuniyu@...gle.com>,
	<aleksander.lobakin@...el.com>, <toke@...hat.com>, <lorenzo@...nel.org>,
	<netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
	<syzbot+ff145014d6b0ce64a173@...kaller.appspotmail.com>
Subject: Re: [PATCH net v2] xdp: update mem type when page pool is used for
 generic XDP

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...