Re: [PATCH v2 3/4] xen/arm: Reserve domid 0 for Dom0

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.04.2021 11:48, Luca Fancellu wrote:
> --- a/xen/common/domctl.c
> +++ b/xen/common/domctl.c
> @@ -419,7 +419,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
> u_domctl)
>              {
>                  if ( dom == DOMID_FIRST_RESERVED )
>                      dom = 1;
> -                if ( is_free_domid(dom) )
> +                if ( (dom != 0) && is_free_domid(dom) )
>                      break;
>              }
>  

I don't think this change is needed - I don't see how dom could
ever end up being zero. The code is already intended to be safe
wrt accidentally creating a domain with ID zero. (Granted "rover"
would benefit from being moved into the yet more narrow scope,
which would make this even more obvious.)

Jan