Re: [Xen-devel] [PATCH 12/20] xen: avoid calling rcu_lock_*target_domain when an XSM hook exists

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.09.12 at 21:49, Daniel De Graaf <dgdegra@xxxxxxxxxxxxx> wrote:
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -195,30 +195,6 @@ double_gt_unlock(struct grant_table *lgt, struct 
> grant_table *rgt)
>          spin_unlock(&rgt->lock);
>  }
>  
> -static struct domain *gt_lock_target_domain_by_id(domid_t dom)
> -{
> -    struct domain *d;
> -    int rc = GNTST_general_error;
> -
> -    switch ( rcu_lock_target_domain_by_id(dom, &d) )
> -    {
> -    case 0:
> -        return d;
> -
> -    case -ESRCH:
> -        gdprintk(XENLOG_INFO, "Bad domid %d.\n", dom);
> -        rc = GNTST_bad_domain;
> -        break;
> -
> -    case -EPERM:
> -        rc = GNTST_permission_denied;
> -        break;
> -    }
> -
> -    ASSERT(rc < 0 && -rc <= MAX_ERRNO);
> -    return ERR_PTR(rc);
> -}
> -

Removing that function again is fine as long as you retain the
distinguished error codes, which ...

>  static inline int
>  __get_maptrack_handle(
>      struct grant_table *t)
> @@ -1304,11 +1280,12 @@ gnttab_setup_table(
>          goto out1;
>      }
>  
> -    d = gt_lock_target_domain_by_id(op.dom);
> -    if ( IS_ERR(d) )
> +    d = rcu_lock_domain_by_any_id(op.dom);
> +    if ( d == NULL )
>      {
> -        op.status = PTR_ERR(d);
> -        goto out1;
> +        gdprintk(XENLOG_INFO, "Bad domid %d.\n", op.dom);
> +        op.status = GNTST_bad_domain;

... you don't.

> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -570,7 +570,8 @@ long do_memory_op(unsigned long cmd, 
> XEN_GUEST_HANDLE(void) arg)
>               && (reservation.mem_flags & XENMEMF_populate_on_demand) )
>              args.memflags |= MEMF_populate_on_demand;
>  
> -        if ( unlikely(rcu_lock_target_domain_by_id(reservation.domid, &d)) )
> +        d = rcu_lock_domain_by_any_id(reservation.domid);
> +        if ( d == NULL )
>              return start_extent;
>          args.domain = d;
>  
> @@ -619,9 +620,9 @@ long do_memory_op(unsigned long cmd, 
> XEN_GUEST_HANDLE(void) arg)
>          if ( copy_from_guest(&domid, arg, 1) )
>              return -EFAULT;
>  
> -        rc = rcu_lock_target_domain_by_id(domid, &d);
> -        if ( rc )
> -            return rc;
> +        d = rcu_lock_domain_by_any_id(domid);
> +        if ( d == NULL )
> +            return -ESRCH;

And quite similarly here and further down you're losing -EPERM.

Jan


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