Re: [PATCH] KVM: X86: Fix softlockup when get the current kvmclock timestamp

[Paolo Bonzini]

On 06/11/2017 11:06, Wanpeng Li wrote:
> 2017-11-06 17:29 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>:
>> On 06/11/2017 01:55, Wanpeng Li wrote:
>>> This can be reproduced when running kvm-unit-tests/hyperv_stimer.flat and
>>> cpu-hotplug stress simultaneously. kvm_get_time_scale() takes too long which
>>> results in softlockup.
>>
>> Apart from the pr_debug, kvm_get_time_scale should take less than a
>> microsecond.  The patch is fine, but can you confirm that pr_debug is
>> the culprit?
> 
> I can still encounter softlockup after removing the pr_debug.

Is kvm_get_time_scale getting into an infinite loop then?  That would be
the actual bug.

Paolo