Ok, here is what i found so far: the problem lies in the 'thunderx_zip' driver, that is the driver for the hw accelerated zip compressor / decompressor ip block - it kicks in once we select the deflate method for the zram device.
How way to reproduce it: # modprobe zram # echo 1 > /sys/block/zram0/reset # echo deflate > /sys/block/zram0/comp_algorithm # echo 128M > /sys/block/zram0/disksize # mkfs.ext4 -F /dev/zram0 [stuck forever here] Two trivial workarounds: -blacklist the thunderx_zip kmod: # rmmod thunderx_zip # echo 'blacklist thunderx_zip' >> /etc/modprobe.d/blacklist.conf or -disable the CRYPTO_DEV_CAVIUM_ZIP kconfig (and void building thunderx_zip kmod) and recompile As to what is causing it, till yesterday, it appeared as the problem was connected to the arm64 kpti but now i'm sure it is not: the problem started to appear in 4.13.0-37-generic #42, while 4.13.0-36-generic #40 was immune and the only difference between those two kernels is the arm64 kpti patchset. You can easily reproduce it in the upstream stable/linux-4.14.y tree too (4.14.26 is affected for example). $ make defconfig $ echo "CONFIG_CRYPTO_DEV_CAVIUM_ZIP=m" >> .config $ make oldconfig build and install as usual, and then try the reproducer above. But what i found this morning, is that even the original 4.14.0 release is affected, but that release clearly doesn't contain the kpti patches. Now what i want to try is: 1) test it on different hardware (one thing that i noticed is that if the thunderx_zip kmod is loaded at boot or later in the board life cycle, that slightly changes the error and that smells a lot like memory corruption) 2) test it with 4.15x and 4.16 I'll write another update when i have more data. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1755073 Title: ubuntu_zram_smoke test will cause soft lockup on Artful ThunderX ARM64 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1755073/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
