[Bug 196149] New: QEMU causes a host hang / reset on PPC64EL when used in KVM + HV mode (kvm_hv module)

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=196149

            Bug ID: 196149
           Summary: QEMU causes a host hang / reset on PPC64EL when used
                    in KVM + HV mode (kvm_hv module)
           Product: Virtualization
           Version: unspecified
    Kernel Version: 4.9
          Hardware: PPC-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: tpearson@raptorengineering.com
        Regression: No

QEMU causes a host hang / reset on PPC64EL when used in KVM + HV mode (kvm_hv
module) on host kernels with a page size of 4k.

After a random amount of uptime, starting new QEMU virtual machines will cause
the host to experience a soft CPU lockup. Depending on configuration and other
random factors the host will either checkstop and reboot, or hang indefinitely.
The following stacktrace was pulled from an instance where the host simply hung
after starting a fourth virtual machine.

Command line:

qemu-system-ppc64 --enable-kvm -M pseries -cpu host -m 8G -realtime mlock=on
-kernel vmlinux-4.7.0-1-powerpc64le -initrd initrd.img-4.7.0-1-powerpc64le

Host kernel stack trace:

[ 1067.451053] INFO: rcu_sched self-detected stall on CPU
[ 1067.452646]  32-...: (5249 ticks this GP) idle=b4d/140000000000001/0
softirq=2214/2214 fqs=2576
[ 1067.454256]   (t=5251 jiffies g=13030 c=13029 q=127812)
[ 1067.455057] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 1067.455062]  32-...: (5249 ticks this GP) idle=b4d/140000000000001/0
softirq=2214/2214 fqs=2576
[ 1067.455076]  (detected by 16, t=5252 jiffies, g=13030, c=13029, q=127812)
[ 1067.455078] Task dump for CPU 32:
[ 1067.455081] qemu-system-ppc R  running task        0  4426   4324 0x00040004
[ 1067.455082] Call Trace:
[ 1067.455087] [c000001f6cd13550] [0000000000000003] 0x3 (unreliable)
[ 1067.466157] Task dump for CPU 32:
[ 1067.466160] qemu-system-ppc R  running task        0  4426   4324 0x00040004
[ 1067.466161] Call Trace:
[ 1067.466168] [c000001f6cd133d0] [c00000000010d484] sched_show_task+0xe4/0x150
(unreliable)
[ 1067.466172] [c000001f6cd13440] [c000000000836918]
rcu_dump_cpu_stacks+0xf4/0x140
[ 1067.466175] [c000001f6cd13490] [c00000000015a064]
rcu_check_callbacks+0x9f4/0xb40
[ 1067.466178] [c000001f6cd135c0] [c000000000162394]
update_process_times+0x44/0x90
[ 1067.466180] [c000001f6cd135f0] [c000000000179bd8]
tick_sched_handle.isra.4+0x48/0xe0
[ 1067.466183] [c000001f6cd13630] [c000000000179cd4] tick_sched_timer+0x64/0xd0
[ 1067.466185] [c000001f6cd13670] [c0000000001633d4]
__hrtimer_run_queues+0x124/0x420
[ 1067.466187] [c000001f6cd13700] [c00000000016407c]
hrtimer_interrupt+0xec/0x2b0
[ 1067.466191] [c000001f6cd137c0] [c000000000026bec]
__timer_interrupt+0x8c/0x270
[ 1067.466197] [c000001f6cd13810] [c00000000002721c] timer_interrupt+0x9c/0xe0
[ 1067.466200] [c000001f6cd13840] [c000000000009550]
decrementer_common+0x150/0x180
[ 1067.466209] --- interrupt: 901 at kvmppc_hv_get_dirty_log+0x1c8/0x510
[kvm_hv]
                   LR = kvmppc_hv_get_dirty_log+0x1f4/0x510 [kvm_hv]
[ 1067.466212] [c000001f6cd13be0] [d00000001a889620]
kvm_vm_ioctl_get_dirty_log_hv+0xd8/0x180 [kvm_hv]
[ 1067.466218] [c000001f6cd13c30] [d00000001a832268]
kvm_vm_ioctl_get_dirty_log+0x40/0x60 [kvm]
[ 1067.466223] [c000001f6cd13c60] [d00000001a826bcc] kvm_vm_ioctl+0x524/0x8f0
[kvm]
[ 1067.466227] [c000001f6cd13d40] [c0000000003234f8] do_vfs_ioctl+0xd8/0x8c0
[ 1067.466230] [c000001f6cd13de0] [c000000000323db4] SyS_ioctl+0xd4/0xf0
[ 1067.466233] [c000001f6cd13e30] [c00000000000bd60] system_call+0x38/0xfc

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