arm64: 4.14 of_match_node() issues

[Robin Murphy]

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 :(

Robin.