Re: [BUG] Migration hv_time rollback

[Antoine Damhet]

On Wed, Sep 16, 2020 at 02:50:56PM +0200, Vitaly Kuznetsov wrote:
[...]

> >>
> >
> >
> > Oh, I think I see what's going on. When you add 'kvm=off'
> > cpu->env.features[FEAT_KVM] is reset (see x86_cpu_expand_features()) so
> > kvmclock QEMU device is not created and nobody calls KVM_SET_CLOCK on
> > migration.
> >
> > In case we really want to support 'kvm=off' I think we can add Hyper-V
> > features check here along with KVM, this should do the job.
> 
> Does the untested
> 
> diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
> index 64283358f91d..e03b2ca6d8f6 100644
> --- a/hw/i386/kvm/clock.c
> +++ b/hw/i386/kvm/clock.c
> @@ -333,8 +333,9 @@ void kvmclock_create(void)
>      X86CPU *cpu = X86_CPU(first_cpu);
>  
>      if (kvm_enabled() &&
> -        cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) |
> -                                       (1ULL << KVM_FEATURE_CLOCKSOURCE2))) {
> +        ((cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) |
> +                                         (1ULL << 
> KVM_FEATURE_CLOCKSOURCE2))) ||
> +         (cpu->env.features[FEAT_HYPERV_EAX] & 
> HV_TIME_REF_COUNT_AVAILABLE))) {
>          sysbus_create_simple(TYPE_KVM_CLOCK, -1, NULL);
>      }
>  }
> 
> help?

It appears to work :)

> 
> (I don't think we need to remove all 'if (kvm_enabled())' checks from
> machine types as 'kvm=off' should not be related).

Indeed (I didn't look at the macro, it was just quick & dirty).

> 
> -- 
> Vitaly
> 
> 

-- 
Antoine 'xdbob' Damhet

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