RHEL 8.1 Oops on qemu-ppc-for-4.2

[Paul Clarke]

I'm using RHEL 8.1 with TCG on a very recent qemu-ppc-for-4.2. HEAD:
--
commit 9b4efa2ede5db24377405a21b218066b90fe2f0e
Date:   Mon Dec 9 16:06:51 2019 +0000

    Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2019-12-09' into 
staging
--

It generally runs well for some time, but then I get an Oops at random (or 
possibly when idle for some time):
--
[O[11316.307334] Oops: Exception in kernel mode, sig: 4 [#1]
[11316.316415] LE SMP NR_CPUS=2048 NUMA pSeries
[11316.319519] Modules linked in: nf_tables_set nft_fib_inet nft_fib_ipv4 
nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject 
nft_ct nft_chain_nat_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 
nft_chain_route_ipv6 nft_chain_nat_ipv4 nf_conntrack_ipv4 nf_defrag_ipv4 
nf_nat_ipv4 nf_nat nft_chain_route_ipv4 nf_conntrack ip6_tables ip_tables 
nft_compat ip_set nf_tables nfnetlink xts sg vmx_crypto virtio_balloon 
virtio_console isofs xfs libcrc32c sr_mod cdrom bochs_drm drm_kms_helper 
syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm virtio_net 
drm_panel_orientation_quirks virtio_blk net_failover failover virtio_scsi
[11316.331431] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.18.0-147.el8.ppc64le 
#1
[11316.332660] NIP:  c0000000000515ec LR: c0000000000fa778 CTR: c0000000000fa750
[11316.333655] REGS: c00000000166f900 TRAP: 0700   Not tainted  
(4.18.0-147.el8.ppc64le)
[11316.334536] MSR:  800000000288b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>  CR: 
44000822  XER: 00000000
[11316.335802] CFAR: c0000000000515a0 IRQMASK: 1 
[11316.335802] GPR00: c0000000000fa778 c00000000166fb80 c000000001672900 
0000000028000000 
[11316.335802] GPR04: c0000000016a1fe8 0000000000000000 c0000000ffffc000 
0000000000000001 
[11316.335802] GPR08: c000000001a90000 0000000000000000 0000000000000001 
c00000017fdc3100 
[11316.335802] GPR12: c0000000000fa750 c000000001a90000 0000000002f66f60 
c00000017fdd8980 
[11316.335802] GPR16: 00000000030324b0 c0000000015ae199 0000000000000000 
0000000000000004 
[11316.335802] GPR20: 0000000000000000 c00000000160b9a8 0000000000000001 
c00000017fdd8a00 
[11316.335802] GPR24: c00000000166fd90 c000000000d45188 c0000000016a2350 
0000000000000002 
[11316.335802] GPR28: c000000001839100 c0000000016a24b4 0000000000000000 
0000000000000000 
[11316.342836] NIP [c0000000000515ec] doorbell_try_core_ipi+0x9c/0xb0
[11316.343482] LR [c0000000000fa778] smp_pseries_cause_ipi+0x28/0x70
[11316.344093] Call Trace:
[11316.344511] [c00000000166fb80] [c00000000166fc20] init_stack+0x3c20/0x4000 
(unreliable)
[11316.345193] [c00000000166fbb0] [c000000000056d3c] 
smp_send_reschedule+0xac/0xc0
[11316.345750] [c00000000166fbd0] [c00000000019a5b4] kick_ilb+0x124/0x150
[11316.346247] [c00000000166fc20] [c0000000001ada04] 
pick_next_task_fair+0x7f4/0x840
[11316.346822] [c00000000166fd30] [c000000000d4429c] __schedule+0x15c/0xb20
[11316.347376] [c00000000166fe00] [c000000000d45188] schedule_idle+0x38/0x70
[11316.347866] [c00000000166fe20] [c000000000199144] do_idle+0x274/0x480
[11316.348323] [c00000000166fea0] [c00000000019958c] cpu_startup_entry+0x3c/0x40
[11316.348813] [c00000000166fed0] [c0000000000103d8] rest_init+0xe0/0xf8
[11316.349281] [c00000000166ff00] [c0000000010b4228] start_kernel+0x638/0x658
[11316.349786] [c00000000166ff90] [c00000000000ad7c] 
start_here_common+0x1c/0x520
[11316.350340] Instruction dump:
[11316.350755] 3929dac0 78681f24 38e00001 e8c60000 81290000 7d06402a 3929ffff 
7d231838 
[11316.351331] 98e81025 7c0004ac 5463017e 64632800 <7c00191c> 7d435378 4e800020 
60000000 
[11316.352386] ---[ end trace af78a85a10eb57cc ]---
[11316.361536] 
[11317.362388] Kernel panic - not syncing: Fatal exception
--

Coincidentally, this was up for about pi (3.14) hours.  Before that, I had 
pulled and rebuilt because I was seeing Oopses, so I don't think the Oops is 
related to a recent change.

Let me know how I can help figure out what's going on.

PC