John Paul Adrian Glaubitz <glaub...@physik.fu-berlin.de> writes:
> Hi Michael!
Hi Adrian,
Thanks for testing ...
>> The Linux kernel for powerpc since v5.2 has a bug which allows a
>> malicious KVM guest to crash the host, when the host is running on
>> Power8.
>>
>> Only machines using Linux as the hypervisor, aka. KVM, powernv or bare
>> metal, are affected by the bug. Machines running PowerVM are not
>> affected.
>>
>> The bug was introduced in:
>>
>> 10d91611f426 ("powerpc/64s: Reimplement book3s idle code in C")
>>
>> Which was first released in v5.2.
>>
>> The upstream fix is:
>>
>> cdeb5d7d890e ("KVM: PPC: Book3S HV: Make idle_kvm_start_guest() return 0
>> if it went to guest")
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cdeb5d7d890e14f3b70e8087e745c4a6a7d9f337
>>
>> Which will be included in the v5.16 release.
>
> I have tested these patches against 5.14 but it seems the problem [1] still
> remains for me
> for big-endian guests. I built a patched kernel yesterday, rebooted the KVM
> server and let
> the build daemons do their work over night.
>
> When I got up this morning, I noticed the machine was down, so I checked the
> serial console
> via IPMI and saw the same messages again as reported in [1]:
>
> [41483.963562] watchdog: BUG: soft lockup - CPU#104 stuck for 25521s!
> [migration/104:175]
> [41507.963307] watchdog: BUG: soft lockup - CPU#104 stuck for 25544s!
> [migration/104:175]
> [41518.311200] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [41518.311216] rcu: 136-...0: (135 ticks this GP)
> idle=242/1/0x4000000000000000 softirq=32031/32033 fqs=2729959
> [41547.962882] watchdog: BUG: soft lockup - CPU#104 stuck for 25581s!
> [migration/104:175]
> [41571.962627] watchdog: BUG: soft lockup - CPU#104 stuck for 25603s!
> [migration/104:175]
> [41581.330530] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [41581.330546] rcu: 136-...0: (135 ticks this GP)
> idle=242/1/0x4000000000000000 softirq=32031/32033 fqs=2736378
> [41611.962202] watchdog: BUG: soft lockup - CPU#104 stuck for 25641s!
> [migration/104:175]
> [41635.961947] watchdog: BUG: soft lockup - CPU#104 stuck for 25663s!
> [migration/104:175]
> [41644.349859] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [41644.349876] rcu: 136-...0: (135 ticks this GP)
> idle=242/1/0x4000000000000000 softirq=32031/32033 fqs=2742753
> [41671.961564] watchdog: BUG: soft lockup - CPU#104 stuck for 25697s!
> [migration/104:175]
> [41695.961309] watchdog: BUG: soft lockup - CPU#104 stuck for 25719s!
> [migration/104:175]
> [41707.369190] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [41707.369206] rcu: 136-...0: (135 ticks this GP)
> idle=242/1/0x4000000000000000 softirq=32031/32033 fqs=2749151
> [41735.960884] watchdog: BUG: soft lockup - CPU#104 stuck for 25756s!
> [migration/104:175]
> [41759.960629] watchdog: BUG: soft lockup - CPU#104 stuck for 25778s!
> [migration/104:175]
> [41770.388520] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [41770.388548] rcu: 136-...0: (135 ticks this GP)
> idle=242/1/0x4000000000000000 softirq=32031/32033 fqs=2755540
> [41776.076307] rcu: rcu_sched kthread timer wakeup didn't happen for 1423
> jiffies! g49897 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
> [41776.076327] rcu: Possible timer handling issue on cpu=32
> timer-softirq=1056014
> [41776.076336] rcu: rcu_sched kthread starved for 1424 jiffies! g49897 f0x0
> RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=32
> [41776.076350] rcu: Unless rcu_sched kthread gets sufficient CPU time,
> OOM is now expected behavior.
> [41776.076360] rcu: RCU grace-period kthread stack dump:
> [41776.076434] rcu: Stack dump where RCU GP kthread last ran:
> [41783.960374] watchdog: BUG: soft lockup - CPU#104 stuck for 25801s!
> [migration/104:175]
> [41807.960119] watchdog: BUG: soft lockup - CPU#104 stuck for 25823s!
> [migration/104:175]
> [41831.959864] watchdog: BUG: soft lockup - CPU#104 stuck for 25846s!
> [migration/104:175]
> [41833.407851] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [41833.407868] rcu: 136-...0: (135 ticks this GP)
> idle=242/1/0x4000000000000000 softirq=32031/32033 fqs=2760381
> [41863.959524] watchdog: BUG: soft lockup - CPU#104 stuck for 25875s!
> [migration/104:175]
>
> It seems that in this case, it was the testsuite of the git package [2] that
> triggered the bug. As you
> can see from the overview, the git package has been in the building state for
> 8 hours meaning the
> build server crashed and is no longer giving feedback to the database.
OK, that sucks.
I did test the repro case you gave me before (in the bugzilla), which
was building glibc, that passes for me with a patched host.
I guess we have yet another bug.
I tried the following in a debian BE VM and it completed fine:
$ dget -u http://ftp.debian.org/debian/pool/main/g/git/git_2.33.1-1.dsc
$ sbuild -d sid --arch=powerpc --no-arch-all git_2.33.1-1.dsc
Same for ppc64.
And I also tried both at once, repeatedly in a loop.
I guess it's something more complicated.
What exact host/guest kernel versions and configs are you running?
cheers
