<html>
<head>
<base href="https://bugs.dpdk.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8" class="bz_new_table">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_UNCONFIRMED "
title="UNCONFIRMED - Segmentation fault encountered in MPRQ vectorized mode"
href="https://bugs.dpdk.org/show_bug.cgi?id=1776">1776</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Segmentation fault encountered in MPRQ vectorized mode
</td>
</tr>
<tr>
<th>Product</th>
<td>DPDK
</td>
</tr>
<tr>
<th>Version</th>
<td>22.11
</td>
</tr>
<tr>
<th>Hardware</th>
<td>x86
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>UNCONFIRMED
</td>
</tr>
<tr>
<th>Severity</th>
<td>critical
</td>
</tr>
<tr>
<th>Priority</th>
<td>Normal
</td>
</tr>
<tr>
<th>Component</th>
<td>ethdev
</td>
</tr>
<tr>
<th>Assignee</th>
<td>dev@dpdk.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>canary.overflow@gmail.com
</td>
</tr>
<tr>
<th>Target Milestone</th>
<td>---
</td>
</tr></table>
<p>
<div class="bz_comment_block">
<pre class="bz_comment_text">I have been encountering segmentation fault when running DPDK in MPRQ
vectorized mode. To reproduce the issue on testpmd, run with the following
parameters:
dpdk-testpmd -l 1-5 -n 4 -a
0000:1f:00.0,rxq_comp_en=1,rxq_pkt_pad_en=1,rxqs_min_mprq=1,mprq_en=1,mprq_log_stride_num=6,mprq_log_stride_size=9,mprq_max_memcpy_len=64,rx_vec_en=1
-- -i --rxd=8192 --max-pkt-len=9000 --rxq=1 --total-num-mbufs=16384
--mbuf-size=3000 --enable-drop-en –-enable-scatter
This segmentation fault goes away when I disable vectorization (rx_vec_en=0).
(Note that the segmentation fault does not occur in forward-mode=rxonly). The
segmentation fault also seems to happen with higher chances when there is a
rxnombuf.
The backtrace of the segmentation fault was:
#0 0x0000000001c34912 in __rte_pktmbuf_free_extbuf ()
#1 0x0000000001c36a10 in rte_pktmbuf_detach ()
#2 0x0000000001c4a9ec in rxq_copy_mprq_mbuf_v ()
#3 0x0000000001c4d63b in rxq_burst_mprq_v ()
#4 0x0000000001c4d7a7 in mlx5_rx_burst_mprq_vec ()
#5 0x000000000050be66 in rte_eth_rx_burst ()
#6 0x000000000050c53d in pkt_burst_io_forward ()
#7 0x00000000005427b4 in run_pkt_fwd_on_lcore ()
#8 0x000000000054289b in start_pkt_forward_on_core ()
#9 0x0000000000a473c9 in eal_thread_loop ()
#10 0x00007ffff60061ca in start_thread () from /lib64/libpthread.so.0
#11 0x00007ffff5c72e73 in clone () from /lib64/libc.so.6
*Note that the addresses may not be exact as I've added some log statements and
attempted fixes previously (they were commented out when I obtained this
backtrace).
Upon some investigation, I noticed that in DPDK’s source codes
drivers/net/mlx5/mlx5_rxtx_vec.c (function rxq_copy_mprq_mbuf_v()), there is a
possibility where the consumed stride exceeds the stride number (64 in this
case) which should not be happening. I'm suspecting that there's some CQE
misalignment here upon encountering rxnombuf.
rxq_copy_mprq_mbuf_v(...) {
...
if(rxq->consumed_strd == strd_n) {
// replenish WQE
}
...
strd_cnt = (elts[i]->pkt_len / strd_sz) +
((elts[i]->pkt_len % strd_sz) ? 1 : 0);
rxq_code = mprq_buf_to_pkt(rxq, elts[i], elts[i]->pkt_len, buf,
rxq->consumed_strd, strd_cnt);
rxq->consumed_strd += strd_cnt; // encountering cases where
rxq->consumed_strd > strd_n
...
}
In addition, there were also cases in mprq_buf_to_pkt() where the allocated seg
address is exactly the same as the pkt (elts[i]) address passed in which should
not happen.
mprq_buf_to_pkt(...) {
...
if(hdrm_overlap > 0) {
MLX5_ASSERT(rxq->strd_scatter_en);
struct rte_mbuf *seg = rte_pktmbuf_alloc(rxq->mp);
if (unlikely(seg == NULL)) return MLX5_RXQ_CODE_NOMBUF;
SET_DATA_OFF(seg, 0);
// added debug statement
// saw instances where pkt = seg
DRV_LOG(DEBUG, "pkt %p seg %p", (void *)pkt, (void *)seg);
rte_memcpy(rte_pktmbuf_mtod(seg, void *), RTE_PTR_ADD(addr, len -
hdrm_overlap), hdrm_overlap);
...
}
}
I have tried upgrading my DPDK version to 24.11 but the segmentation fault
still persists.
</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are the assignee for the bug.</li>
</ul>
<div itemscope itemtype="http://schema.org/EmailMessage">
<div itemprop="action" itemscope itemtype="http://schema.org/ViewAction">
<link itemprop="url" href="https://bugs.dpdk.org/show_bug.cgi?id=1776">
<meta itemprop="name" content="View bug">
</div>
<meta itemprop="description" content="Bugzilla bug update notification">
</div>
</body>
</html>