Re: [Xen-devel] [PATCH v8 04/11] xen: evtchn: make evtchn_reset() ready for soft reset

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Jun 23, 2015 at 06:11:46PM +0200, Vitaly Kuznetsov wrote:
> We need to close all event channel so the domain performing soft reset
> will be able to open them back.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
>  xen/common/event_channel.c | 38 +++++++++++++++++++-------------------
>  xen/include/xen/event.h    |  3 +++
>  2 files changed, 22 insertions(+), 19 deletions(-)
> 
> diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
> index 2208de0..894bdf2 100644
> --- a/xen/common/event_channel.c
> +++ b/xen/common/event_channel.c
> @@ -937,26 +937,19 @@ int evtchn_unmask(unsigned int port)
>  }
>  
>  
> -static long evtchn_reset(evtchn_reset_t *r)
> +void evtchn_reset(struct domain *d)
>  {
> -    domid_t dom = r->dom;
> -    struct domain *d;
> -    int i, rc;
> -
> -    d = rcu_lock_domain_by_any_id(dom);
> -    if ( d == NULL )
> -        return -ESRCH;
> +    unsigned int i;
>  
> -    rc = xsm_evtchn_reset(XSM_TARGET, current->domain, d);
> -    if ( rc )
> -        goto out;
> +    if ( d != current->domain )
> +        domain_pause(d);

That is a bit of blocking operation. Could it be an requirement
that the domain has to be paused before this operation is done?

As in:

        if ( d != current->domain && !d->controller_pause_count)
        {
                return -EINVAL;
        }
and then there is no need for the domain_pause/unpause business
here.
>  
>      for ( i = 0; port_is_valid(d, i); i++ )
>          (void)__evtchn_close(d, i);
>  
>      spin_lock(&d->event_lock);
>  
> -    if ( (dom == DOMID_SELF) && d->evtchn_fifo )
> +    if ( d->evtchn_fifo )
>      {
>          /*
>           * Guest domain called EVTCHNOP_reset with DOMID_SELF, destroying

You should also update the comment saying 'DOMID_SELF' as now
it can be another domain doing it as well.

> @@ -969,12 +962,8 @@ static long evtchn_reset(evtchn_reset_t *r)
>  
>      spin_unlock(&d->event_lock);
>  
> -    rc = 0;
> -
> -out:
> -    rcu_unlock_domain(d);
> -
> -    return rc;
> +    if ( d != current->domain )
> +        domain_unpause(d);
>  }
>  
>  static long evtchn_set_priority(const struct evtchn_set_priority 
> *set_priority)
> @@ -1099,9 +1088,20 @@ long do_event_channel_op(int cmd, 
> XEN_GUEST_HANDLE_PARAM(void) arg)
>  
>      case EVTCHNOP_reset: {
>          struct evtchn_reset reset;
> +        struct domain *d;
> +
>          if ( copy_from_guest(&reset, arg, 1) != 0 )
>              return -EFAULT;
> -        rc = evtchn_reset(&reset);
> +
> +        d = rcu_lock_domain_by_any_id(reset.dom);
> +        if ( d == NULL )
> +            return -ESRCH;
> +
> +        rc = xsm_evtchn_reset(XSM_TARGET, current->domain, d);
> +        if ( !rc )
> +            evtchn_reset(d);
> +
> +        rcu_unlock_domain(d);
>          break;
>      }
>  
> diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
> index af923d1..b99e19b 100644
> --- a/xen/include/xen/event.h
> +++ b/xen/include/xen/event.h
> @@ -126,6 +126,9 @@ void evtchn_check_pollers(struct domain *d, unsigned int 
> port);
>  
>  void evtchn_2l_init(struct domain *d);
>  
> +/* Close all event channels and reset to 2-level ABI */
> +void evtchn_reset(struct domain *d);
> +
>  /*
>   * Low-level event channel port ops.
>   */
> -- 
> 2.4.2
> 

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