Re: [PATCH] KVM: VMX: Do not overwrite vcpu->srcu_idx in vmx_vcpu_reset

[Gleb Natapov <gleb@redhat.com>]

On Thu, Mar 14, 2013 at 04:08:42PM +0100, Paolo Bonzini wrote:
> Il 14/03/2013 16:03, Jan Kiszka ha scritto:
> >> > vcpu->srcu_idx = srcu_read_lock()
> >> >   idx = srcu_read_lock(&vcpu->kvm->srcu); 
> >> >    srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> >> >    vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> >> >   srcu_read_unlock(&vcpu->kvm->srcu, idx);
> >> > srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> >> > 
> >> > Not sure this is valid.
> > Grmbl, likely not.
> 
> It might be.
> 
> Isn't it the same as two different CPUs doing
> 
> CPU 1                                                 CPU 2
> ------------------------------------------------------------------------------------------------
> 
> vcpu->srcu_idx = srcu_read_lock()
>                                                       idx = srcu_read_lock(&vcpu->kvm->srcu); 
> srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
>                                                       srcu_read_unlock(&vcpu->kvm->srcu, idx);
> srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> 
> ?
> 
Srcu may have per cpu state. We can always ask Paul.

--
			Gleb.