Re: [PATCH 2/4] xen: introduce grant_map_exists

["Jan Beulich" <JBeulich@suse.com>]

>>> On 02.10.14 at 12:02, <stefano.stabellini@eu.citrix.com> wrote:
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -484,6 +484,38 @@ static int _set_status(unsigned gt_version,
>          return _set_status_v2(domid, readonly, mapflag, shah, act, status);
>  }
>  
> +bool_t grant_map_exists(struct domain *ld,
> +                        struct grant_table *rgt,
> +                        unsigned long mfn)
> +{
> +    struct active_grant_entry *act;
> +    grant_ref_t ref;
> +    bool_t ret = 0;
> +
> +    spin_lock(&rgt->lock);
> +
> +    for ( ref = 0; ref != nr_grant_entries(rgt); ref++ )
> +    {
> +        act = &active_entry(rgt, ref);
> +
> +        if ( !act->pin )
> +            continue;
> +
> +        if ( act->domid != ld->domain_id )
> +            continue;
> +
> +        if ( act->frame != mfn )
> +            continue;
> +        
> +        ret = 1;
> +        break;
> +    }
> +
> +    spin_unlock(&rgt->lock);
> +
> +    return ret;

By the time you get here the information you return is stale. Is that
not a problem for the caller? And if it's not, why would it check in the
first place?

Jan