Re: [Qemu-devel] [RFC] arm/cpu: fix soft lockup panic after resuming from stop

[Heyi Guo]

Hi Richard,



On 2019/3/12 22:59, Richard Henderson wrote:
> On 3/12/19 12:57 AM, Heyi Guo wrote:
> >   int kvm_arm_vcpu_init(CPUState *cs)
> >   {
> >       ARMCPU *cpu = ARM_CPU(cs);
> >       struct kvm_vcpu_init init;
> >   
> > +    /*
> > +     * Only add change state handler for arch timer once, for KVM will help to
> > +     * synchronize virtual timer of all VCPUs.
> > +     */
> > +    static bool arch_timer_change_state_handler_added;
> > +
> > +
> > +    if (!arch_timer_change_state_handler_added) {
> > +        qemu_add_vm_change_state_handler(arch_timer_change_state_handler, cs);
> > +        arch_timer_change_state_handler_added = true;
> > +    }
> Which means that this will not trigger for the second time that you pause the
> vm.  You need to key this off of something else, like cpu id 0.
I don't quite understand. Do you mean the handler will be deactivated after one 
trigger? Or something else?

I suppose the state change handler will take effect for the whole VM life time, 
so I believed one handler for one VM is enough, in whichever vCPU 
initialization it is created. I also tested several times for one VM, and 
fortunately the rough code worked.

Thanks,

Heyi

> r~