arm64: 4.14 of_match_node() issues

[Marek Szyprowski]

Hi All,

On 2017-10-09 14:04, Robin Murphy wrote:
> On 09/10/17 11:58, Robin Murphy wrote:
>> On 09/10/17 10:24, Will Deacon wrote:
>>> Hi Andreas,
>>>
>>> On Sat, Oct 07, 2017 at 02:42:13AM +0200, Andreas Färber wrote:
>>>> Since 4.14-rc1 I am seeing frequent oopses during module loading (e.g.,
>>>> MMC, USB) from initrd on aarch64. Symptoms are similar to this in -rc3:
>>>>
>>>> [  OK  ] Started udev Coldplug all Devices.
>>>> [   10.117775] usbcore: registered new interface driver usbfs
>>>> [   10.118235] Unable to handle kernel paging request at virtual address
>>>> ffff000008e5abc0
>>>> [   10.118238] Mem abort info:
>>>> [   10.118245]   Exception class = DABT (current EL), IL = 32 bits
>>>> [   10.118249]   SET = 0, FnV = 0
>>>> [   10.118253]   EA = 0, S1PTW = 0
>>>> [   10.118256] Data abort info:
>>>> [   10.118261]   ISV = 0, ISS = 0x00000006
>>>> [   10.118264]   CM = 0, WnR = 0
>>>> [   10.118274] swapper pgtable: 4k pages, 48-bit VAs, pgd = ffff0000094a5000
>>>> [   10.118279] [ffff000008e5abc0] *pgd=00000000bfffe003,
>>>> *pud=00000000bfffd003, *pmd=0000000000000000
>>>> [   10.118299] Internal error: Oops: 96000006 [#1] SMP
>>>> [   10.118305] Modules linked in: fixed usbcore(+) sunxi_mmc mmc_core
>>>> phy_sun4i_usb sg
>>>> [   10.118341] CPU: 3 PID: 49 Comm: kworker/3:1 Not tainted
>>>> 4.14.0-rc3-2.gf27997b-default #1
>>>> [   10.118345] Hardware name: sunxi sunxi/sunxi, BIOS 2017.05-rc1 04/13/2017
>>>> [   10.118369] Workqueue: events deferred_probe_work_func
>>>> [   10.118378] task: ffff80007c8f4000 task.stack: ffff0000099d8000
>>>> [   10.118394] PC is at __of_match_node.part.1+0x48/0x88
>>>> [   10.118403] LR is at of_match_node+0x40/0x70
>>>> [   10.118411] pc : [<ffff00000879aed0>] lr : [<ffff00000879af50>]
>>> [...]
>>>
>>>> This has been observed on Pine64 (>60%; also by Stefan) and Odroid-C2;
>>>> my other arm64 boards such as Raspberry Pi 3 have not run into this so
>>>> far. No such problems on 32-bit boards.
>>>>
>>>> This is using the openSUSE config:
>>>> https://kernel.opensuse.org/cgit/kernel-source/plain/config/arm64/default
>>> Hmm, hard to know what to suggest without a concrete reproducer. Do you know
>>> which driver is being probed in the log above? Also, does this still break
>>> if you pass "keepinitrd" on the cmdline? Finally, can you dump the kernel
>>> virtual memory layout, please?
>> FWIW, this looks a lot like what happens when a built-in driver's
>> of_match_table is marked __init, but for whatever reason (deferred probe
>> etc.) winds up getting poked by a module load after it no longer exists.
> Heh, synchronicity...
>
> https://lists.linuxfoundation.org/pipermail/iommu/2017-October/024572.html
>
> Looks like we either have to revert plenty of patches from the const
> brigade, avoid freeing init, or come up with some way to make the driver
> core cleverer about the whole deal :(

It's not that bad. I did a quick check with

# git grep "of_device_id.*init"

and Exynos SYSMMU driver was the only candidate for a fix. Maybe someone
else should double check that list to make sure that there is no other
platform device/driver related code there.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland