Comment 0 for bug 1979296

---Problem Description---
rcu_sched self-detected stall with Secure Execution

When the system is busy and additional Secure Execution guests are started, the LPAR crashes.
Christian Borntraeger looked at the stack trace and identified two commits which should fix the issue:

1e2aa46de526a5adafe580bca4c25856bb06f09e
and
f0a1a0615a6ff6d38af2c65a522698fb4bb85df6

Please include these two fixes into 20.04, and 18.04 HWE.

Here the stack trace:

[592792.725078] rcu: INFO: rcu_sched self-detected stall on CPU
[592792.725089] rcu: 4-....: (2099 ticks this GP) idle=7d2/1/0x4000000000000002 softirq=3920041/3920042 fqs=984
[592792.725133] (t=2100 jiffies g=26268505 q=410280)
[592792.725135] Task dump for CPU 4:
[592792.725137] qemu-system-s39 R running task 0 2557923 1644255 0x06000004
[592792.725139] Call Trace:
[592792.725146] ([<000000566e2dcf52>] show_stack+0x7a/0xc0)
[592792.725150] [<000000566dab696c>] sched_show_task.part.0+0xdc/0x100
[592792.725151] [<000000566e2df248>] rcu_dump_cpu_stacks+0xc0/0x100
[592792.725154] [<000000566db0510c>] rcu_sched_clock_irq+0x75c/0x980
[592792.725156] [<000000566db1326c>] update_process_times+0x3c/0x80
[592792.725160] [<000000566db24fea>] tick_sched_handle.isra.0+0x4a/0x70
[592792.725161] [<000000566db2528e>] tick_sched_timer+0x5e/0xc0
[592792.725163] [<000000566db14294>] __hrtimer_run_queues+0x114/0x2f0
[592792.725165] [<000000566db14fdc>] hrtimer_interrupt+0x12c/0x2a0
[592792.725167] [<000000566da14b6a>] do_IRQ+0xaa/0xb0
[592792.725170] [<000000566e2eed08>] ext_int_handler+0x130/0x134
[592792.725174] [<000000566da2bad8>] gmap_make_secure+0x1c8/0x340
[592792.725175] ([<000000566da2b9fe>] gmap_make_secure+0xee/0x340)
[592792.725180] [<000000566da6e796>] kvm_s390_pv_unpack+0xc6/0x2b0
[592792.725183] [<000000566da535c0>] kvm_s390_handle_pv+0x390/0x580
[592792.725184] [<000000566da55b30>] kvm_arch_vm_ioctl+0x250/0x9e0
[592792.725187] [<000000566da44c26>] kvm_vm_ioctl+0x396/0x760
[592792.725191] [<000000566dceb0b6>] do_vfs_ioctl+0x376/0x690
[592792.725193] [<000000566dceb454>] ksys_ioctl+0x84/0xb0
[592792.725194] [<000000566dceb4ea>] __s390x_sys_ioctl+0x2a/0x40
[592792.725195] [<000000566e2ee6b2>] system_call+0x2a6/0x2c8

Contact Information = <email address hidden>, <email address hidden>

---uname output---
5.4.0-90-generic #101-Ubuntu

Machine Type = 8562 A00-GT2

---System Hang---
 LPAR crashed and needed to be re-booted

---Debugger---
 A debugger is not configured

---Steps to Reproduce---
 Cause high load. Then start Secure Execution enabled KVM guest