On 04.05.22 09:37, Janosch Frank wrote: > On 5/3/22 23:55, Liam Howlett wrote: >> * Heiko Carstens <hca@xxxxxxxxxxxxx> [220503 15:49]: >>> On Mon, May 02, 2022 at 08:50:04PM +0200, Heiko Carstens wrote: >>>> On Mon, May 02, 2022 at 01:31:00PM +0000, Liam Howlett wrote: >>>>> * Heiko Carstens <hca@xxxxxxxxxxxxx> [220502 06:18]: >>>>>> On Sun, May 01, 2022 at 05:24:12PM -0700, Andrew Morton wrote: >>>>>>> (cc S390 maintainers) >>>>>>> (cc stable & Greg) >>> ... >>>>>>>> booting. The last thing I see is: >>>>>>>> >>>>>>>> "[ 4.668916] Spectre V2 mitigation: execute trampolines" >>>>>>>> >>>>>>>> I've bisected back to commit e553f62f10d9 (mm, page_alloc: fix >>>>>>>> build_zonerefs_node()) >>>>>>>> >>>>>>>> With the this commit, I am unable to boot one out of three times. When >>>>>>>> using the previous commit I was not able to get it to hang after trying >>>>>>>> 10+ times. This is a qemu s390 install with KASAN on and I see no error >>>>>>>> messages. I think it's likely it is this patch, but no guaranteed. >>> ... >>>>>> Liam, could you share your kernel config? >>>>> >>>>> Sure thing. See attached. >>>> >>>> So, I can reproduce the hanging system now. However this looks like a >>>> qemu problem on s390, since I can reproduce this only with Qemu+TCG. >>>> Qemu with kvm works without any problems (same if I use z/VM as >>>> hypervisor). >>>> >>>> Janosch, Claudio, can you have a look at this please? >>> >>> So, at least for me this problem also exists with plain v5.17. >>> Switching off KASAN, or alternatively switching to KASAN_INLINE >>> "fixes" it for me with Qemu+TCG. >>> >>> Liam, could you please also try to disable KASAN in your config? With >>> that I think we can be almost sure this could be some bug in Qemu. >> >> With KASAN, my tree fails 100% of the time (mm-stable + my maple tree >> patches) >> >> Without KASAN, it boots 100% of the time. >> >> I think this verifies with you say above? >> >> Thanks, >> Liam > > I had a short look yesterday and the boot usually hangs in the raid6 > code. Disabling vector instructions didn't make a difference but a few > interruptions via GDB solve the problem for some reason. > > CCing David and Thomas for TCG > I somehow recall that KASAN was always disabled under TCG, I might be wrong (I thought we'd get a message early during boot that the HW doesn't support KASAN). I recall that raid code is a heavy user of vector instructions. How can I reproduce? Compile upstream (or -next?) with kasan support and run it under TCG? -- Thanks, David / dhildenb
