Re: [Xen-devel] [PATCH V2] xen: Fix BUFIOREQ evtchn init for a stubdom.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.06.12 at 17:21, Anthony PERARD <anthony.perard@xxxxxxxxxx> wrote:
> @@ -3777,17 +3792,21 @@ long do_hvm_op(unsigned long op, 
> XEN_GUEST_HANDLE(void) arg)
>                  iorp = &d->arch.hvm_domain.ioreq;
>                  for_each_vcpu ( d, v )
>                  {
> -                    int old_port, new_port;
> -                    new_port = alloc_unbound_xen_event_channel(
> -                        v, a.value, NULL);
> -                    if ( new_port < 0 )
> -                    {
> -                        rc = new_port;
> +                    rc = hvm_replace_event_channel(v, a.value,
> +                                                   
> &v->arch.hvm_vcpu.xen_port);
> +                    if ( rc )
>                          break;
> +
> +                    if ( v->vcpu_id == 0 )

Don't you also have to check params[HVM_PARAM_BUFIOREQ_EVTCHN]
is valid (as otherwise free_xen_event_channel() will BUG_ON() on
it)?

> +                    {
> +                        spin_lock(&iorp->lock);
> +                        rc = hvm_replace_event_channel(v, a.value,
> +                            
> (int*)&v->domain->arch.hvm_domain.params[HVM_PARAM_BUFIOREQ_EVTCHN]);
> +                        spin_unlock(&iorp->lock);
> +                        if ( rc )
> +                            break;
>                      }

My first preference would be for this to be moved out of the
loop. If it has to remain in the loop for some reason, then the
next best option would be to move this into the iorp->lock
protected region immediately below.

Jan

> -                    /* xchg() ensures that only we free_xen_event_channel() 
> */
> -                    old_port = xchg(&v->arch.hvm_vcpu.xen_port, new_port);
> -                    free_xen_event_channel(v, old_port);
> +
>                      spin_lock(&iorp->lock);
>                      if ( iorp->va != NULL )
>                          get_ioreq(v)->vp_eport = v->arch.hvm_vcpu.xen_port;



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