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Subject: Re: Kernel Panic in skb_release_data using genet
To:     Maxime Ripard <maxime@cerno.tech>,
        Florian Fainelli <f.fainelli@gmail.com>
Cc:     Doug Berger <opendmb@gmail.com>,
        bcm-kernel-feedback-list@broadcom.com,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        Nicolas Saenz Julienne <nsaenz@kernel.org>
References: <20210524130147.7xv6ih2e3apu2zvu@gilmour>
 <a53f6192-3520-d5f8-df4b-786b3e4e8707@gmail.com>
 <20210524151329.5ummh4dfui6syme3@gilmour>
From:   Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <1482eff4-c5f4-66d9-237c-55a096ae2eb4@gmail.com>
Date:   Mon, 24 May 2021 08:37:48 -0700
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On 5/24/2021 8:13 AM, Maxime Ripard wrote:
> Hi Florian,
> 
> On Mon, May 24, 2021 at 07:49:25AM -0700, Florian Fainelli wrote:
>> Hi Maxime,
>>
>> On 5/24/2021 6:01 AM, Maxime Ripard wrote:
>>> Hi Doug, Florian,
>>>
>>> I've been running a RaspberryPi4 with a mainline kernel for a while,
>>> booting from NFS. Every once in a while (I'd say ~20-30% of all boots),
>>> I'm getting a kernel panic around the time init is started.
>>>
>>> I was debugging a kernel based on drm-misc-next-2021-05-17 today with
>>> KASAN enabled and got this, which looks related:
>>
>> Is there a known good version that could be used for bisection or you
>> just started to do this test and you have no reference point?
> 
> I've had this issue for over a year and never (I think?) got a good
> version, so while it might be a regression, it's not a recent one.

OK, this helps and does not really help.

> 
>> How stable in terms of clocking is the configuration that you are using?
>> I could try to fire up a similar test on a Pi4 at home, or use one of
>> our 72112 systems which is the closest we have to a Pi4 and see if that
>> happens there as well.
> 
> I'm not really sure about the clocking. Is there any clock you want to
> look at in particular?

ARM, DDR, AXI, anything that could cause some memory corruption to occur
essentially. GENET clocks are fairly fixed, you have a 250MHz clock and
a 125MHz clock feeding the data path.

> 
> My setup is fairly simple: the firmware and kernel are loaded over TFTP
> and the rootfs is mounted over NFS, and the crash always occur around
> init start, so I guess when it actually starts to transmit a decent
> amount of data?

Do you reproduce this problem with KASAN disabled, do you eventually
have a crash pointing back to the same location?

I have a suspicion that this is all Pi4 specific because we regularly
run the GENET driver through various kernel versions (4.9, 5.4 and 5.10
and mainline) and did not run into that.
-- 
Florian