Subject: Re: [PATCH net-next v25 08/13] net: add support for skbs with unreadable frags

From: Jakub Kicinski <[email-masked]>
Date: Mon, 9 Sep 2024 18:57:48 -0700

On Mon,  9 Sep 2024 05:43:13 +0000 Mina Almasry wrote:
> For device memory TCP, we expect the skb headers to be available in host
> memory for access, and we expect the skb frags to be in device memory
> and unaccessible to the host. We expect there to be no mixing and
> matching of device memory frags (unaccessible) with host memory frags
> (accessible) in the same skb.
> 
> Add a skb->devmem flag which indicates whether the frags in this skb
> are device memory frags or not.
> 
> __skb_fill_netmem_desc() now checks frags added to skbs for net_iov,
> and marks the skb as skb->devmem accordingly.
> 
> Add checks through the network stack to avoid accessing the frags of
> devmem skbs and avoid coalescing devmem skbs with non devmem skbs.
> 
> Signed-off-by: Willem de Bruijn <[email-masked]>
> Signed-off-by: Kaiyuan Zhang <[email-masked]>
> Signed-off-by: Mina Almasry <[email-masked]>
> Reviewed-by: Eric Dumazet <[email-masked]>

I'm sure we'll find more cases which need a check but I can't think 
of any now, so:

Reviewed-by: Jakub Kicinski <[email-masked]>