Messages in this thread | | | Subject | Re: Kernel Panic in skb_release_data using genet | From | Florian Fainelli <> | Date | Fri, 28 May 2021 09:48:14 -0700 |
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On 5/28/21 9:32 AM, Maxime Ripard wrote: > hi Florian, > > On Fri, May 28, 2021 at 09:21:27AM -0700, Florian Fainelli wrote: >> On 5/24/21 8:37 AM, Florian Fainelli wrote: >>> >>> >>> 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. >> >> I have not had time to get a set-up to reproduce what you are seeing, >> could you share your .config meanwhile? Thanks > > Sorry, I didn't have the time to check how the clock were behaving. > > You'll find attached my config.txt file and .config > > I'm booting the board entirely from TFTP (which might introduce some > issues in the "handoff" from the bootloader to the kernel), you'll find > some guide there: > > https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/net_tutorial.md
That is also how I boot my Pi4 at home, and I suspect you are right, if the VPU does not shut down GENET's DMA, and leaves buffer addresses in the on-chip descriptors that point to an address space that is managed totally differently by Linux, then we can have a serious problem and create some memory corruption when the ring is being reclaimed. I will run a few experiments to test that theory and there may be a solution using the SW_INIT reset controller to have a big reset of the controller before handing it over to the Linux driver. -- Florian
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