From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [qemu-system-x86:10185]
CPU: 6 PID: 10185 Comm: qemu-system-x86 Tainted: G OE 4.14.0-rc4+ #4
RIP: 0010:kvm_get_time_scale+0x4e/0xa0 [kvm]
Call Trace:
? get_kvmclock_ns+0xa3/0x140 [kvm]
get_time_ref_counter+0x5a/0x80 [kvm]
kvm_hv_process_stimers+0x120/0x5f0 [kvm]
? kvm_hv_process_stimers+0x120/0x5f0 [kvm]
? preempt_schedule+0x27/0x30
? ___preempt_schedule+0x16/0x18
kvm_arch_vcpu_ioctl_run+0x4b4/0x1690 [kvm]
? kvm_arch_vcpu_load+0x47/0x230 [kvm]
kvm_vcpu_ioctl+0x33a/0x620 [kvm]
? kvm_vcpu_ioctl+0x33a/0x620 [kvm]
? kvm_vm_ioctl_check_extension_generic+0x3b/0x40 [kvm]
? kvm_dev_ioctl+0x279/0x6c0 [kvm]
do_vfs_ioctl+0xa1/0x5d0
? __fget+0x73/0xa0
SyS_ioctl+0x79/0x90
entry_SYSCALL_64_fastpath+0x1e/0xa9
This can be reproduced when running kvm-unit-tests/hyperv_stimer.flat and
cpu-hotplug stress simultaneously. __this_cpu_read(cpu_tsc_khz) returns 0
(set in kvmclock_cpu_down_prep()) when the pCPU is unhotplug which results
in kvm_get_time_scale() gets into an infinite loop.
This patch fixes it by skipping to fill the hv_clock when the pCPU is offline.
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
---
v1 -> v2:
* avoid infinite loop
arch/x86/kvm/x86.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 03869eb..d2507c6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1259,6 +1259,9 @@ static void kvm_get_time_scale(uint64_t scaled_hz, uint64_t base_hz,
uint64_t tps64;
uint32_t tps32;
+ if (unlikely(base_hz == 0))
+ return;
+
tps64 = base_hz;
scaled64 = scaled_hz;
while (tps64 > scaled64*2 || tps64 & 0xffffffff00000000ULL) {
--
2.7.4
