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From: Thomas Monjalon <thomas@monjalon.net>
To: Ruifeng Wang <Ruifeng.Wang@arm.com>,
	Min Zhou <zhoumin@loongson.cn>,
	dev@dpdk.org, "Zhang, Qi Z" <qi.z.zhang@intel.com>
Cc: "mb@smartsharesystems.com" <mb@smartsharesystems.com>,
	"konstantin.v.ananyev@yandex.ru" <konstantin.v.ananyev@yandex.ru>,
	"Yang, Qiming" <qiming.yang@intel.com>,
	"Wu, Wenjun1" <wenjun1.wu@intel.com>,
	 "drc@linux.vnet.ibm.com" <drc@linux.vnet.ibm.com>,
	"roretzla@linux.microsoft.com" <roretzla@linux.microsoft.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"stable@dpdk.org" <stable@dpdk.org>,
	"maobibo@loongson.cn" <maobibo@loongson.cn>, nd <nd@arm.com>,
	david.marchand@redhat.com
Subject: Re: [PATCH v3] net/ixgbe: add proper memory barriers for some Rx functions
Date: Mon, 12 Jun 2023 12:26:06 +0200	[thread overview]
Message-ID: <3202143.AJdgDx1Vlc@thomas> (raw)
In-Reply-To: <DM4PR11MB59940F773E4CEF01650A392BD7789@DM4PR11MB5994.namprd11.prod.outlook.com>

15/05/2023 04:10, Zhang, Qi Z:
> From: Ruifeng Wang <Ruifeng.Wang@arm.com>
> > From: Min Zhou <zhoumin@loongson.cn>
> > >
> > > Segmentation fault has been observed while running the
> > > ixgbe_recv_pkts_lro() function to receive packets on the Loongson
> > > 3C5000 processor which has 64 cores and 4 NUMA nodes.
> > >
> > > From the ixgbe_recv_pkts_lro() function, we found that as long as the
> > > first packet has the EOP bit set, and the length of this packet is
> > > less than or equal to rxq->crc_len, the segmentation fault will
> > > definitely happen even though on the other platforms. For example, if
> > > we made the first packet which had the EOP bit set had a zero length by
> > force, the segmentation fault would happen on X86.
> > >
> > > Because when processd the first packet the first_seg->next will be
> > > NULL, if at the same time this packet has the EOP bit set and its
> > > length is less than or equal to rxq->crc_len, the following loop will be
> > executed:
> > >
> > >     for (lp = first_seg; lp->next != rxm; lp = lp->next)
> > >         ;
> > >
> > > We know that the first_seg->next will be NULL under this condition. So
> > > the expression of
> > > lp->next->next will cause the segmentation fault.
> > >
> > > Normally, the length of the first packet with EOP bit set will be
> > > greater than rxq-
> > > >crc_len. However, the out-of-order execution of CPU may make the read
> > > >ordering of the
> > > status and the rest of the descriptor fields in this function not be
> > > correct. The related codes are as following:
> > >
> > >         rxdp = &rx_ring[rx_id];
> > >  #1     staterr = rte_le_to_cpu_32(rxdp->wb.upper.status_error);
> > >
> > >         if (!(staterr & IXGBE_RXDADV_STAT_DD))
> > >             break;
> > >
> > >  #2     rxd = *rxdp;
> > >
> > > The sentence #2 may be executed before sentence #1. This action is
> > > likely to make the ready packet zero length. If the packet is the
> > > first packet and has the EOP bit set, the above segmentation fault will
> > happen.
> > >
> > > So, we should add a proper memory barrier to ensure the read ordering
> > > be correct. We also did the same thing in the ixgbe_recv_pkts()
> > > function to make the rxd data be valid even though we did not find
> > segmentation fault in this function.
> > >
> > > Fixes: 8eecb3295ae ("ixgbe: add LRO support")
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: Min Zhou <zhoumin@loongson.cn>
> > > ---
> > > v3:
> > > - Use rte_smp_rmb() as the proper memory barrier instead of rte_rmb()
> > > ---
> > > v2:
> > > - Make the calling of rte_rmb() for all platforms
> > > ---
[...]
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> 
> Applied to dpdk-next-net-intel.
> 
> Thanks
> Qi
> 

Why ignoring checkpatch?
It is saying:
"
Warning in drivers/net/ixgbe/ixgbe_rxtx.c:
Using rte_smp_[r/w]mb
"

Ruifeng proposed "rte_atomic_thread_fence(__ATOMIC_ACQUIRE)"
in a comment on the v2.

I will drop this patch from the pull of next-net-intel branch.



  reply	other threads:[~2023-06-12 10:26 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-24  9:05 [PATCH v2] " Min Zhou
2023-04-28  3:43 ` Zhang, Qi Z
2023-04-28  6:27   ` Morten Brørup
2023-05-04 12:58     ` zhoumin
2023-05-04 12:42   ` zhoumin
2023-05-01 13:29 ` Konstantin Ananyev
2023-05-04  6:13   ` Ruifeng Wang
2023-05-05  1:45     ` zhoumin
2023-05-04 13:16   ` zhoumin
2023-05-04 13:21     ` Morten Brørup
2023-05-04 13:33       ` Zhang, Qi Z
2023-05-05  2:42         ` zhoumin
2023-05-06  1:30           ` Zhang, Qi Z
2023-05-05  1:54       ` zhoumin
2023-05-06 10:23 ` [PATCH v3] " Min Zhou
2023-05-08  6:03   ` Ruifeng Wang
2023-05-15  2:10     ` Zhang, Qi Z
2023-06-12 10:26       ` Thomas Monjalon [this message]
2023-06-12 11:58         ` zhoumin
2023-06-12 12:44           ` Thomas Monjalon
2023-06-13  1:42             ` zhoumin
2023-06-13  3:30               ` Jiawen Wu
2023-06-13 10:12                 ` zhoumin
2023-06-14 10:58               ` Konstantin Ananyev
2023-06-13  9:25             ` Ruifeng Wang
2023-06-20 15:52               ` Thomas Monjalon
2023-06-21  6:50                 ` Ruifeng Wang
2023-06-13  9:44   ` [PATCH v4] " Min Zhou
2023-06-13 10:20     ` Ruifeng Wang
2023-06-13 12:11       ` Zhang, Qi Z

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