Re: [Xen-devel] [PATCH v5 7/8] libxl/libxc: Move libxl_get_numainfo()'s hypercall buffer management to libxc

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 03/20/2015 09:56 AM, Ian Campbell wrote:
> On Thu, 2015-03-19 at 17:54 -0400, Boris Ostrovsky wrote:
> > diff --git a/tools/libxc/xc_misc.c b/tools/libxc/xc_misc.c
> > index 411128e..607ae61 100644
> > --- a/tools/libxc/xc_misc.c
> > +++ b/tools/libxc/xc_misc.c
> > @@ -209,22 +209,49 @@ out:
> >       return ret;
> >   }
> >   
> > -int xc_numainfo(xc_interface *xch,
> > -                xc_numainfo_t *put_info)
> > +int xc_numainfo(xc_interface *xch, unsigned *max_nodes,
> > +                xc_meminfo_t *meminfo, uint32_t *distance)
> >   {
> >       int ret;
> >       DECLARE_SYSCTL;
> > +    DECLARE_HYPERCALL_BOUNCE(meminfo, *max_nodes * sizeof(*meminfo),
> > +                             XC_HYPERCALL_BUFFER_BOUNCE_OUT);
> > +    DECLARE_HYPERCALL_BOUNCE(distance,
> > +                             *max_nodes * *max_nodes * sizeof(*distance),
> > +                             XC_HYPERCALL_BUFFER_BOUNCE_OUT);
> >   
> > -    sysctl.cmd = XEN_SYSCTL_numainfo;
> > +    if (meminfo && distance) {
> > +        if ((ret = xc_hypercall_bounce_pre(xch, meminfo)))
> > +            goto out;
> > +        if ((ret = xc_hypercall_bounce_pre(xch, distance)))
> > +            goto out;
> Same comment about handling NULL as before.
>
> In addition what if only one of meminfo and distance is NULL? Is that
> valid or do you need a !!meminfo ^ !!distance check?
I want to treat this as as an error here, which is why I have
        } else if (meminfo || distance) {
            errno = EINVAL;
            return -1;
        }

because the hypervisor will only attempt to copy numainfo things when 
both are valid. Otherwise (i.e. even if only one is a NULL) it will 
assume that this is a request for size. The alternative would be to add 
another error there, which I decided not to do.
-boris

> Rests looks ok.

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