Re: [Xen-devel] [PATCH v2] x86/vpmu: add cpu hot unplug notifier for vpmu

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.05.17 at 17:57, <luwei.kang@xxxxxxxxx> wrote:
> @@ -581,9 +582,14 @@ static void vpmu_arch_destroy(struct vcpu *v)
>  
>      if ( vpmu->arch_vpmu_ops && vpmu->arch_vpmu_ops->arch_vpmu_destroy )
>      {
> -        /* Unload VPMU first. This will stop counters */
> -        on_selected_cpus(cpumask_of(vcpu_vpmu(v)->last_pcpu),
> -                         vpmu_save_force, v, 1);
> +        /*
> +         * Unload VPMU first if VPMU_CONTEXT_LOADED being set.
> +         * This will stop counters.
> +         */
> +        if ( vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
> +            on_selected_cpus(cpumask_of(vcpu_vpmu(v)->last_pcpu),
> +                             vpmu_save_force, v, 1);
> +
>           vpmu->arch_vpmu_ops->arch_vpmu_destroy(v);
>      }
>  }

So this is a good step towards what was requested during v1 review,
provided it is correct (I'll let Boris comment). You didn't, however, do
anything about the other unguarded last_pcpu uses (in vpmu_load()
and upwards from the code above in vpmu_arch_destroy()). These
_may_ be implicitly fine, but if so please at least add suitable
ASSERT()s.

Jan


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