netdev - Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE

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Message-ID: <CAHS8izPF7WjMKLA82fy5LjE9XzUWNVMgs9tD7JM5UY3xfw93Yw@mail.gmail.com>
Date: Wed, 5 Jul 2023 18:19:00 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: David Ahern <dsahern@...nel.org>
Cc: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Jesper Dangaard Brouer <jbrouer@...hat.com>, brouer@...hat.com, 
	Alexander Duyck <alexander.duyck@...il.com>, Yunsheng Lin <linyunsheng@...wei.com>, davem@...emloft.net, 
	pabeni@...hat.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Lorenzo Bianconi <lorenzo@...nel.org>, Yisen Zhuang <yisen.zhuang@...wei.com>, 
	Salil Mehta <salil.mehta@...wei.com>, Sunil Goutham <sgoutham@...vell.com>, 
	Geetha sowjanya <gakula@...vell.com>, Subbaraya Sundeep <sbhatta@...vell.com>, 
	hariprasad <hkelam@...vell.com>, Saeed Mahameed <saeedm@...dia.com>, 
	Leon Romanovsky <leon@...nel.org>, Felix Fietkau <nbd@....name>, Ryder Lee <ryder.lee@...iatek.com>, 
	Shayne Chen <shayne.chen@...iatek.com>, Sean Wang <sean.wang@...iatek.com>, 
	Kalle Valo <kvalo@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, 
	linux-rdma@...r.kernel.org, linux-wireless@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
	Jonathan Lemon <jonathan.lemon@...il.com>
Subject: Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5]
 page_pool: remove PP_FLAG_PAGE_FRAG flag)

On Mon, Jul 3, 2023 at 10:23 AM David Ahern <dsahern@...nel.org> wrote:
>
> On 7/3/23 11:13 AM, Eric Dumazet wrote:
> > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> > index a2dbeb264f260e5b8923ece9aac99fe19ddfeb62..aa4133d1b1e0676e408499ea4534b51262394432
> > 100644
> > --- a/net/packet/af_packet.c
> > +++ b/net/packet/af_packet.c
> > @@ -2152,7 +2152,7 @@ static int packet_rcv(struct sk_buff *skb,
> > struct net_device *dev,
> >                 }
> >         }
> >
> > -       snaplen = skb->len;
> > +       snaplen = skb->devmem ? skb_headlen(skb) : skb->len;
> >
>
> Ok, so you expect a flag on the skb noting the use of 'untouchable'
> memory. That aligns with my expectations based on POCs.
>
> Based on the above: 1) skb->head is expected to be host memory, and 2)
> the flag is a global for all frags, so no mix and match.

Yes, both are correct (i.e. what I plan to propose).

-- 
Thanks,
Mina