Re: [PATCH v5 net 1/1] net: mvpp2: fix XDP rx queues registering

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Dec 10, 2021 at 06:16:20PM +0100, Louis Amas wrote:
> commit a50e659b2a1be14784e80f8492aab177e67c53a2 upstream
> 
> The registration of XDP queue information is incorrect because the
> RX queue id we use is invalid. When port->id == 0 it appears to works
> as expected yet it's no longer the case when port->id != 0.
> 
> The problem arised while using a recent kernel version on the
> MACCHIATOBin. This board has several ports:
>  * eth0 and eth1 are 10Gbps interfaces ; both ports has port->id == 0;
>  * eth2 is a 1Gbps interface with port->id != 0.
> 
> Code from xdp-tutorial (more specifically advanced03-AF_XDP) was used
> to test packet capture and injection on all these interfaces. The XDP
> kernel was simplified to:
> 
> 	SEC("xdp_sock")
> 	int xdp_sock_prog(struct xdp_md *ctx)
> 	{
> 		int index = ctx->rx_queue_index;
> 
> 		/* A set entry here means that the correspnding queue_id
> 		* has an active AF_XDP socket bound to it. */
> 		if (bpf_map_lookup_elem(&xsks_map, &index))
> 			return bpf_redirect_map(&xsks_map, index, 0);
> 
> 		return XDP_PASS;
> 	}
> 
> Starting the program using:
> 
> 	./af_xdp_user -d DEV
> 
> Gives the following result:
> 
>  * eth0 : ok
>  * eth1 : ok
>  * eth2 : no capture, no injection
> 
> Investigating the issue shows that XDP rx queues for eth2 are wrong:
> XDP expects their id to be in the range [0..3] but we found them to be
> in the range [32..35].
> 
> Trying to force rx queue ids using:
> 
> 	./af_xdp_user -d eth2 -Q 32
> 
> fails as expected (we shall not have more than 4 queues).
> 
> When we register the XDP rx queue information (using
> xdp_rxq_info_reg() in function mvpp2_rxq_init()) we tell it to use
> rxq->id as the queue id. This value is computed as:
> 
> 	rxq->id = port->id * max_rxq_count + queue_id
> 
> where max_rxq_count depends on the device version. In the MACCHIATOBin
> case, this value is 32, meaning that rx queues on eth2 are numbered
> from 32 to 35 - there are four of them.
> 
> Clearly, this is not the per-port queue id that XDP is expecting:
> it wants a value in the range [0..3]. It shall directly use queue_id
> which is stored in rxq->logic_rxq -- so let's use that value instead.
> 
> rxq->id is left untouched ; its value is indeed valid but it should
> not be used in this context.
> 
> This is consistent with the remaining part of the code in
> mvpp2_rxq_init().
> 
> With this change, packet capture is working as expected on all the
> MACCHIATOBin ports.
> 
> Fixes: b27db2274ba8 ("mvpp2: use page_pool allocator")
> Signed-off-by: Louis Amas <louis.amas@eho.link>
> Signed-off-by: Emmanuel Deloget <emmanuel.deloget@eho.link>
> Reviewed-by: Marcin Wojtas <mw@semihalf.com>
> Acked-by: John Fastabend <john.fastabend@gmail.com>
> Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
> ---
> 
> Patch history
> 
> v1 : original submission [1]
> v2 : commit message rework (no change in the patch) [2]
> v3 : commit message rework (no change in the patch) + added Acked-by [3]
> v4 : fix mail corruption by malevolent SMTP + rebase on net/master
> v5 : (this version) add tags back

Now queued up, thanks.

greg k-h