From: Bruce Richardson <bruce.richardson@intel.com>
To: Wang Xiao W <xiao.w.wang@intel.com>
Cc: jing.d.chen@intel.com, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] net/fm10k: fix Rx descriptor read timing
Date: Tue, 5 Jul 2016 10:47:32 +0100 [thread overview]
Message-ID: <20160705094731.GE10232@bricha3-MOBL3> (raw)
In-Reply-To: <20160705094342.GD10232@bricha3-MOBL3>
On Tue, Jul 05, 2016 at 10:43:42AM +0100, Bruce Richardson wrote:
> On Mon, Jul 04, 2016 at 03:51:08PM +0800, Wang Xiao W wrote:
> > We find that when traffic is light, a few amount of packets will be
> > wrongly parsed (e.g. packet type), however this issue will not happen
> > when traffic is heavy.
> >
> > The root cause is some fields in fm10k_rx_desc are read at wrong timing.
> > When the input speed is slower than software's capability, fm10k scalar
> > Rx function accesses descriptors closely to HW, so there's potential
> > sequence: some fields like pkt_info in fm10k_rx_desc are read before HW
> > writeback but some fields like DD bit are read after HW writeback, this
> > will lead to the later packet parsing function using incorrect value.
> >
> > This patch fixes this issue by reading and parsing Rx descriptor after
> > DD bit is set.
> >
> > Fixes: 4b61d3bfa941 ("fm10k: add receive and tranmit")
> > Fixes: c82dd0a7bfa5 ("fm10k: add scatter receive")
> >
> > Signed-off-by: Wang Xiao W <xiao.w.wang@intel.com>
>
> Fix looks correct to me. The key part I think is that the read of the
> descriptor at line "desc = q->hw_ring[next_dd];" is not atomic as it's
> a read of 16B, allowing part of the descriptor to be read either side of
> a HW write-back.
>
> Acked-by: Bruce Richardson <bruce.richardson@intel.com>
>
Applied to dpdk-next-net/rel_16_07
/Bruce
prev parent reply other threads:[~2016-07-05 9:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-04 7:51 Wang Xiao W
2016-07-05 9:43 ` Bruce Richardson
2016-07-05 9:47 ` Bruce Richardson [this message]
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