netdev - Re: [PATCH net-next 6/9] ionic: Add XDP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <e36a0838-8b0f-4240-9aa4-b031b4882507@amd.com>
Date: Thu, 1 Feb 2024 09:41:04 -0800
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, brett.creeley@....com, drivers@...sando.io
Subject: Re: [PATCH net-next 6/9] ionic: Add XDP_TX support

On 1/31/2024 6:25 PM, Jakub Kicinski wrote:
> 
> On Mon, 29 Jan 2024 17:30:39 -0800 Shannon Nelson wrote:
>>        case XDP_TX:
>> +             xdpf = xdp_convert_buff_to_frame(&xdp_buf);
>> +             if (!xdpf)
>> +                     goto out_xdp_abort;
>> +
>> +             txq = rxq->partner;
>> +             nq = netdev_get_tx_queue(netdev, txq->index);
>> +             __netif_tx_lock(nq, smp_processor_id());
>> +
>> +             if (netif_tx_queue_stopped(nq) ||
>> +                 unlikely(ionic_maybe_stop_tx(txq, 1))) {
>> +                     __netif_tx_unlock(nq);
>> +                     goto out_xdp_abort;
>> +             }
>> +
>> +             dma_unmap_page(rxq->dev, buf_info->dma_addr,
>> +                            IONIC_PAGE_SIZE, DMA_FROM_DEVICE);
>> +
>> +             err = ionic_xdp_post_frame(netdev, txq, xdpf, XDP_TX,
>> +                                        buf_info->page,
>> +                                        buf_info->page_offset,
>> +                                        true);
> 
> I think that you need txq_trans_cond_update() somewhere, otherwise
> if XDP starves stack Tx the stack will think the queue is stalled.

Thanks, I'll look into that.


> 
>> +             __netif_tx_unlock(nq);
>> +             if (err) {
>> +                     netdev_dbg(netdev, "tx ionic_xdp_post_frame err %d\n", err);
>> +                     goto out_xdp_abort;
>> +             }
>> +             stats->xdp_tx++;
>> +
>> +             /* the Tx completion will free the buffers */
>> +             break;
>> +
>>        case XDP_ABORTED:
>>        default:
>> -             trace_xdp_exception(netdev, xdp_prog, xdp_action);
>> -             ionic_rx_page_free(rxq, buf_info);
>> -             stats->xdp_aborted++;
>> +             goto out_xdp_abort;
>>        }
>>
>> +     return true;
>> +
>> +out_xdp_abort:
>> +     trace_xdp_exception(netdev, xdp_prog, xdp_action);
>> +     ionic_rx_page_free(rxq, buf_info);
>> +     stats->xdp_aborted++;
>> +
>>        return true;
>>   }
>>
>> @@ -880,6 +1001,16 @@ static void ionic_tx_clean(struct ionic_queue *q,
>>        struct sk_buff *skb = cb_arg;
>>        u16 qi;
>>
>> +     if (desc_info->xdpf) {
>> +             ionic_xdp_tx_desc_clean(q->partner, desc_info);
>> +             stats->clean++;
>> +
>> +             if (unlikely(__netif_subqueue_stopped(q->lif->netdev, q->index)))
>> +                     netif_wake_subqueue(q->lif->netdev, q->index);
>> +
>> +             return;
>> +     }
> 
> You can't complete XDP if NAPI budget is 0, you may be in hard IRQ
> context if its netpoll calling :(

Right - I remember a mention of this a few weeks ago on some other 
driver.  I'll try to dig up the reference and adjust.

Thanks,
sln


>