Re: [PATCH v3] KVM: LAPIC: Recalculate apic map in batch

[Paolo Bonzini]

On 22/06/20 00:26, Igor Mammedov wrote:
> 
> following sequence looks like a race that can cause lost map update events:
> 
>          cpu1                            cpu2
>                              
>                                 apic_map_dirty = true     
>   ------------------------------------------------------------   
>                                 kvm_recalculate_apic_map:
>                                      pass check
>                                          mutex_lock(&kvm->arch.apic_map_lock);
>                                          if (!kvm->arch.apic_map_dirty)
>                                      and in process of updating map
>   -------------------------------------------------------------
>     other calls to
>        apic_map_dirty = true         might be too late for affected cpu
>   -------------------------------------------------------------
>                                      apic_map_dirty = false
>   -------------------------------------------------------------
>     kvm_recalculate_apic_map:
>     bail out on
>       if (!kvm->arch.apic_map_dirty)

I will post a fix for that.  Thanks for the analysis!

Paolo