Re: [Xen-devel] [PATCH 11/20] xen/domctl: Merge set_gnttab_limits into createdomain

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.03.18 at 20:13, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/common/domctl.c
> +++ b/xen/common/domctl.c
> @@ -539,14 +539,37 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
> u_domctl)
>              break;
>          }
>  
> +        /* Stash the new domid for the toolstack. */
> +        op->domain = d->domain_id;
> +        copyback = true;
> +
>          d->max_evtchn_port =
>              min_t(unsigned int, op->u.createdomain.max_evtchn_port, INT_MAX);
>  
> -        ret = 0;
> -        op->domain = d->domain_id;
> -        copyback = 1;
> +        ret = grant_table_set_limits(d, op->u.createdomain.max_grant_frames,
> +                                     op->u.createdomain.max_maptrack_frames);
> +        if ( !ret )
> +            goto createdomain_fail_late;
> +
>          d = NULL;
>          break;
> +
> +    createdomain_fail_late:
> +        /*
> +         * We've hit an error after putting the domain into the domain list,
> +         * meaning that other entities in the system can refer to it.
> +         *
> +         * Unwinding is substantially more complicated, and without
> +         * returning success, the toolstack wont know to clean up.
> +         *
> +         * Reuse the continuation logic to turn this hypercall into a
> +         * destroydomain on behalf of the toolstack.
> +         */
> +        op->cmd = XEN_DOMCTL_destroydomain;
> +        d = NULL;
> +
> +        ret = hypercall_create_continuation(__HYPERVISOR_domctl, "h", 
> u_domctl);
> +        break;
>      }

Nice idea, but what exactly is the reason you can't do this before
inserting the domain into the list?

Jan


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