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Date:   Tue, 9 Nov 2021 16:08:45 +0100
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Subject: Re: [PATCH net] net: stmmac: allow a tc-taprio base-time of zero
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To:     Kurt Kanzenbach <kurt.kanzenbach@linutronix.de>,
        Vladimir Oltean <vladimir.oltean@nxp.com>
Cc:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        Giuseppe Cavallaro <peppe.cavallaro@st.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        "linux-stm32@st-md-mailman.stormreply.com" 
        <linux-stm32@st-md-mailman.stormreply.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Xiaoliang Yang <xiaoliang.yang_1@nxp.com>
References: <20211108202854.1740995-1-vladimir.oltean@nxp.com>
 <87bl2t3fkq.fsf@kurt> <20211109103504.ahl2djymnevsbhoj@skbuf>
 <87h7cl1j41.fsf@kurt>
From:   Yannick Vignon <yannick.vignon@oss.nxp.com>
In-Reply-To: <87h7cl1j41.fsf@kurt>
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Hi Kurt,

On 11/9/2021 3:47 PM, Kurt Kanzenbach wrote:
> On Tue Nov 09 2021, Vladimir Oltean wrote:
>> On Tue, Nov 09, 2021 at 09:20:53AM +0100, Kurt Kanzenbach wrote:
>>> Hi Vladimir,
>>>
>>> On Mon Nov 08 2021, Vladimir Oltean wrote:
>>>> Commit fe28c53ed71d ("net: stmmac: fix taprio configuration when
>>>> base_time is in the past") allowed some base time values in the past,
>>>> but apparently not all, the base-time value of 0 (Jan 1st 1970) is still
>>>> explicitly denied by the driver.
>>>>
>>>> Remove the bogus check.
>>>>
>>>> Fixes: b60189e0392f ("net: stmmac: Integrate EST with TAPRIO scheduler API")
>>>> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
>>>
>>> I've experienced the same problem and wanted to send a patch for
>>> it. Thanks!
>>>
>>> Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
>>
>> Cool. So you had that patch queued up? What other stmmac patches do you
>> have queued up? :).
> 
> I'm experiencing some problems with XDP using this driver. We're
> currently investigating.

Could you elaborate a bit?
I've been using XDP a lot with the stmmac driver recently, and while I 
did see issues initially, most of them got fixed by using a recent 
enough kernel, thanks to the following commits:
. a6451192da2691dcf39507bd ("net: stmmac: fix kernel panic due to NULL 
pointer dereference of xsk_pool")
. 2b9fff64f03219d78044d1ab ("net: stmmac: fix kernel panic due to NULL 
pointer dereference of buf->xdp")
. 81d0885d68ec427e62044cf4 ("net: stmmac: Fix overall budget calculation 
for rxtx_napi")

There was one remaining issue for which I need to push a fix: if you 
remove an XDP program from an interface while transmitting traffic, you 
are likely to trigger a kernel panic. I'll try to push a patch for that 
soon.

> Thanks,
> Kurt
> 

Regards,
Yannick