Linux kernel: powerpc: KVM guest can trigger host crash on Power8

[John Paul Adrian Glaubitz]

Hi Michael!

On 10/28/21 13:20, John Paul Adrian Glaubitz wrote:
> It seems I also can no longer reproduce the issue, even when building the most problematic
> packages and I think we should consider it fixed for now. I will keep monitoring the server,
> of course, and will let you know in case the problem shows again.

The host machine is stuck again but I'm not 100% sure what triggered the problem:

[194817.984249] watchdog: BUG: soft lockup - CPU#80 stuck for 246s! [CPU 2/KVM:1836]
[194818.012248] watchdog: BUG: soft lockup - CPU#152 stuck for 246s! [CPU 3/KVM:1837]
[194825.960164] watchdog: BUG: soft lockup - CPU#24 stuck for 246s! [khugepaged:318]
[194841.983991] watchdog: BUG: soft lockup - CPU#80 stuck for 268s! [CPU 2/KVM:1836]
[194842.011991] watchdog: BUG: soft lockup - CPU#152 stuck for 268s! [CPU 3/KVM:1837]
[194849.959906] watchdog: BUG: soft lockup - CPU#24 stuck for 269s! [khugepaged:318]
[194865.983733] watchdog: BUG: soft lockup - CPU#80 stuck for 291s! [CPU 2/KVM:1836]
[194866.011733] watchdog: BUG: soft lockup - CPU#152 stuck for 291s! [CPU 3/KVM:1837]
[194873.959648] watchdog: BUG: soft lockup - CPU#24 stuck for 291s! [khugepaged:318]
[194889.983475] watchdog: BUG: soft lockup - CPU#80 stuck for 313s! [CPU 2/KVM:1836]
[194890.011475] watchdog: BUG: soft lockup - CPU#152 stuck for 313s! [CPU 3/KVM:1837]
[194897.959390] watchdog: BUG: soft lockup - CPU#24 stuck for 313s! [khugepaged:318]
[194913.983218] watchdog: BUG: soft lockup - CPU#80 stuck for 335s! [CPU 2/KVM:1836]
[194914.011217] watchdog: BUG: soft lockup - CPU#152 stuck for 335s! [CPU 3/KVM:1837]
[194921.959133] watchdog: BUG: soft lockup - CPU#24 stuck for 336s! [khugepaged:318]

The following packages were being built at the same time:

- guest 1: virtuoso-opensource and openturns
- guest 2: llvm-toolchain-13

I really did a lot of testing today with no issues and just after I sent my report
to oss-security that the machine seems to be stable again, the issue showed up :(.

Sorry,
Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz at debian.org
`. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913