Net/igc's rte_eth_rx_burst() never returns packets

[Fabio Fernandes]

Hi Ivan,

Thank you for your response.

I've ran it with the flags you suggested and attached the produced log.

{ sudo ./dpdk-testpmd  --log-level=pmd.net.igc,debug 2>&1; } > testpmd_with_debug_and_rx_print.log;

testpmd_with_debug_and_rx_print.log.zip

However, the driver never reaches point[1] (nor [2]) and this debug line never got logged. I've placed break points to confirm that the loop always exits just before [1], at this check:
```
if (!(staterr & IGC_RXD_STAT_DD))
			break;
```

I've also instrumented testpmd.h as below, to confirm in the log file that RX is called many times and never returns anything but zeros:
```
static inline uint16_t
common_fwd_stream_receive(struct fwd_stream *fs, struct rte_mbuf **burst,
	unsigned int nb_pkts)
{
	uint16_t nb_rx;

	nb_rx = rte_eth_rx_burst(fs->rx_port, fs->rx_queue, burst, nb_pkts);

	// Instrumentation Begin
	{
		static uint64_t g_call_count = 0;
		static uint64_t g_rx_sum = 0;
		g_rx_sum += nb_rx;
		++g_call_count;
		if (nb_rx)
			fprintf(stderr, "rte_eth_rx_burst: %u\n", nb_rx);
		if ((g_call_count % 100000000UL) == 0)
			fprintf(stderr, "g_rx_sum: %lu, g_call_count: %lu\n",
					g_rx_sum, g_call_count);
	}
	// Instrumentation End

	if (record_burst_stats)
		fs->rx_burst_stats.pkt_burst_spread[nb_rx]++;
	fs->rx_packets += nb_rx;
	return nb_rx;
}

```

In regards to [3], I've changed that to use rte_cpu_to_be_32() instead and rebuilt DPDK, but with same results and the loop still always exits there.

I did, however, noticed something strange and this is probably a clue:

Every time I step over this line of `igc_rx_init()` in the debugger:
https://github.com/DPDK/dpdk/blob/v24.03/drivers/net/igc/igc_txrx.c#L1204

```
IGC_WRITE_REG(hw, IGC_RDT(rxq->reg_idx), rxq->nb_rx_desc - 1);
```

I get this in `dmesg` kernel, coming from the igb_uio kernel I've bound to the device I'm testing:

```
[26185.005945] igb_uio 0000:09:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0011 address=0x116141a00 flags=0x0000]
```

The address matches this in the debugger:

```
	rxq->rx_ring_phys_addr
	$1 = 0x116141a00	
	
	rxq->reg_idx
	0

	rxq->nb_rx_desc
	1024	
```

What do you think?

For more info, I'm on this exact DPDK commit:
commit eeb0605f118dae66e80faa44f7b3e88748032353 (HEAD -> v23.11, tag: v23.11

Thanks,
Fabio


Sent with Proton Mail secure email.

On Thursday, August 1st, 2024 at 3:24 PM, Ivan Malov <ivan.malov at arknetworks.am> wrote:

> Hi Fabio,
> 
> Have you tried to specify EAL option --log-level="pmd.net.igc,debug"
> or --log-level='.*',8 when running the application? Perhaps doing
> so can trigger printouts [1], [2]. See if you can't observe those.
> 
> Perhaps consider posting a brief excerpt of your code where
> rte_eth_rx_burst() is invoked and return value is verified.
> 
> Also, albeit unrelated, it's rather peculiar that the code
> does CPU-to-LE conversion [3] of descriptor status, but
> the field itslef is declared as __le32 already: [4].
> 
> [1] https://github.com/DPDK/dpdk/blob/v24.03/drivers/net/igc/igc_txrx.c#L296
> [2] https://github.com/DPDK/dpdk/blob/v24.03/drivers/net/igc/igc_txrx.c#L455
> [3] https://github.com/DPDK/dpdk/blob/v24.03/drivers/net/igc/igc_txrx.c#L264
> [4] https://github.com/DPDK/dpdk/blob/v24.03/drivers/net/igc/base/igc_base.h#L109
> 
> Thank you.
> 
> On Thu, 1 Aug 2024, Fabio Fernandes wrote:
> 
> > Hi,
> > 
> > I have an issue with rte_eth_rx_burst() for IGC poll mode driver never returning any packets and need some advice.
> > I have this network port:
> > 09:00.0 Ethernet controller: Intel Corporation Ethernet Controller I225-V (rev 03)
> > 
> > Bound to igb_uio:
> > Network devices using DPDK-compatible driver
> > ============================================
> > 0000:09:00.0 'Ethernet Controller I225-V 15f3' drv=igb_uio unused=igc
> > 
> > I'm testing this both with testpmd and my own app, which works fine with other drivers such as net/ena and net/i40e. I'm using single RX/TX queue pair with default configs
> > with rte_eth_promiscuous_enable() and rte_eth_allmulticast_enable().
> > 
> > The device seems to rte_eth_dev_start() fine, and rte_eth_stats_get() seem to be detecting inbound packets. Below is the output from testpmd:
> > 
> > Press enter to exiteth_igc_interrupt_action(): Port 0: Link Up - speed 1000 Mbps - full-duplex
> > 
> > Port 0: link state change event
> > ^CTelling cores to stop...
> > Waiting for lcores to finish...
> > 
> > ---------------------- Forward statistics for port 0 ----------------------
> > RX-packets: 129 RX-dropped: 800 RX-total: 929
> > TX-packets: 0 TX-dropped: 0 TX-total: 0
> > ----------------------------------------------------------------------------
> > 
> > +++++++++++++++ Accumulated forward statistics for all ports+++++++++++++++
> > RX-packets: 129 RX-dropped: 800 RX-total: 929
> > TX-packets: 0 TX-dropped: 0 TX-total: 0
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > 
> > Done.
> > 
> > However, rte_eth_rx_burst() never returns anything, neither in testpmd nor in my own app.
> > 
> > In my own app, I log both rte_eth_stats_get() and non-zero xstats from rte_eth_xstats_get_by_id():
> > 
> > 07:02:13.406873186 INF stats.rx : 0
> > 07:02:13.406892616 INF dev_stats.ipackets : 78
> > 07:02:13.406903636 INF dev_stats.opackets : 0
> > 07:02:13.406914166 INF dev_stats.imissed : 0
> > 07:02:13.406924536 INF dev_stats.ierrors : 0
> > 07:02:13.406934116 INF dev_stats.oerrors : 0
> > 07:02:13.406943956 INF dev_stats.rx_nombuf : 0
> > 07:02:13.407247777 INF xstats rx_good_packets : 78
> > 07:02:13.407257147 INF xstats rx_good_bytes : 17205
> > 07:02:13.407265267 INF xstats rx_size_64_packets : 6
> > 07:02:13.407274627 INF xstats rx_size_65_to_127_packets : 31
> > 07:02:13.407285757 INF xstats rx_size_128_to_255_packets : 22
> > 07:02:13.407297537 INF xstats rx_size_256_to_511_packets : 16
> > 07:02:13.407309127 INF xstats rx_size_512_to_1023_packets : 3
> > 07:02:13.407321327 INF xstats rx_broadcast_packets : 8
> > 07:02:13.407331597 INF xstats rx_multicast_packets : 64
> > 07:02:13.407346357 INF xstats rx_total_packets : 78
> > 07:02:13.407355547 INF xstats rx_total_bytes : 17205
> > 07:02:13.407364127 INF xstats rx_sent_to_host_packets : 78
> > 07:02:13.407375347 INF xstats interrupt_assert_count : 1
> > 
> > Still, rte_eth_rx_burst() never returns anything.
> > 
> > It's worthwhile to note that rte_eth_rx_burst() works fine when I, instead of net/igc, use net/ena (with ENA card) or net/i40e (Intel x710 card).
> > 
> > The debug log from EAL and net/igc is attached, in case that helps.
> > There's a warning "igc_rx_init(): forcing scatter mode", but I've already tried changing my mbuf sizes so that the warning goes away but that also didn't help.
> > 
> > Any advice?
> > 
> > Thanks,
> > Fabio
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