netdev - Re: [PATCH net] net: stmmac: Disable Tx queues when reconfiguring the interface

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Message-ID: <fccedd94-d2a8-ed23-852a-2432637adb12@oss.nxp.com>
Date:   Wed, 24 Nov 2021 13:10:55 +0100
From:   Yannick Vignon <yannick.vignon@....nxp.com>
To:     Vladimir Oltean <vladimir.oltean@....com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Kurt Kanzenbach <kurt.kanzenbach@...utronix.de>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        "Sebastien Laveze (OSS)" <sebastien.laveze@....nxp.com>,
        Yannick Vignon <yannick.vignon@....com>
Subject: Re: [PATCH net] net: stmmac: Disable Tx queues when reconfiguring the
 interface

On 11/24/2021 11:06 AM, Vladimir Oltean wrote:
> On Tue, Nov 23, 2021 at 08:07:51PM -0800, Jakub Kicinski wrote:
>> On Tue, 23 Nov 2021 19:54:48 +0100 Yannick Vignon wrote:
>>> From: Yannick Vignon <yannick.vignon@....com>
>>>
>>> The Tx queues were not disabled in cases where the driver needed to stop
>>> the interface to apply a new configuration. This could result in a kernel
>>> panic when doing any of the 3 following actions:
>>> * reconfiguring the number of queues (ethtool -L)
>>> * reconfiguring the size of the ring buffers (ethtool -G)
>>> * installing/removing an XDP program (ip l set dev ethX xdp)
>>>
>>> Prevent the panic by making sure netif_tx_disable is called when stopping
>>> an interface.
>>>
>>> Without this patch, the following kernel panic can be observed when loading
>>> an XDP program:
>>>
>>> Unable to handle kernel paging request at virtual address ffff80001238d040
>>> [....]
>>>   Call trace:
>>>    dwmac4_set_addr+0x8/0x10
>>>    dev_hard_start_xmit+0xe4/0x1ac
>>>    sch_direct_xmit+0xe8/0x39c
>>>    __dev_queue_xmit+0x3ec/0xaf0
>>>    dev_queue_xmit+0x14/0x20
>>> [...]
>>> [ end trace 0000000000000002 ]---
>>>
>>> Fixes: 78cb988d36b6 ("net: stmmac: Add initial XDP support")
>>> Signed-off-by: Yannick Vignon <yannick.vignon@....com>
>>
>> Fixes tag: Fixes: 78cb988d36b6 ("net: stmmac: Add initial XDP support")
>> Has these problem(s):
>> 	- Target SHA1 does not exist
> 
> You caught him backporting! Although I agree, things sent to the "net"
> tree should also be tested against the "net" tree.
> 

That would be more like forward-porting in this case, since I first 
fixed the issue on an older 5.10 kernel :)
And yes, I did reproduce the bug and confirm the fix on the tip of the 
netdev branch yesterday before sending the patch. But I guess I looked 
at the wrong branch when adding the Fixes tag...

Will post a V2 to fix the Fixes tag.