netdev - Re: [PATCH] [PATCH net-next] tun: fix multiqueue rx

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Date:   Sat, 17 Nov 2018 20:39:14 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     werekraken@...il.com
Cc:     jasowang@...hat.com, brouer@...hat.com, mst@...hat.com,
        edumazet@...gle.com, sd@...asysnail.net, netdev@...r.kernel.org,
        matthew.cover@...ckpath.com
Subject: Re: [PATCH] [PATCH net-next] tun: fix multiqueue rx

From: Matthew Cover <werekraken@...il.com>
Date: Thu, 15 Nov 2018 21:10:16 -0700

> When writing packets to a descriptor associated with a combined queue, the
> packets should end up on that queue.
> 
> Before this change all packets written to any descriptor associated with a
> tap interface end up on rx-0, even when the descriptor is associated with a
> different queue.
> 
> The rx traffic can be generated by either of the following.
>   1. a simple tap program which spins up multiple queues and writes packets
>      to each of the file descriptors
>   2. tx from a qemu vm with a tap multiqueue netdev
> 
> The queue for rx traffic can be observed by either of the following (done
> on the hypervisor in the qemu case).
>   1. a simple netmap program which opens and reads from per-queue
>      descriptors
>   2. configuring RPS and doing per-cpu captures with rxtxcpu
> 
> Alternatively, if you printk() the return value of skb_get_rx_queue() just
> before each instance of netif_receive_skb() in tun.c, you will get 65535
> for every skb.
> 
> Calling skb_record_rx_queue() to set the rx queue to the queue_index fixes
> the association between descriptor and rx queue.
> 
> Signed-off-by: Matthew Cover <matthew.cover@...ckpath.com>

As noted by Jason, tun_xdp_one() needs this fix too.

Can you please add that to your patch and resubmit?

Thanks.