Re: [Xen-devel] [PATCH] Event channel request fix

[Stefan Berger <stefanb@xxxxxxxxxx>]

Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote
on 10/06/2005 04:21:02 AM:

> 
> On 6 Oct 2005, at 04:05, Stefan Berger wrote:
> 
> >
> > I compiled Xen for SMP and for some strange reason I could not
always 
> > get the network interface connected to the backend - same for
the TPM 
> > frontend and probably also block frontend. The attached patch
fixes 
> > this problem for all three drivers by explicitly setting the
requested 
> > port for the channel to 0. Since the structure is on the stack
(and 
> > not declared static) all its members should be explicitly initialized.
> > I don't know why I did not encounter this problem on non-SMP
systems 
> > before...
> 
> I broke it yesterday. Previously 'cmd' was statically initialised,
and 
> that caused all other fields to get filled with zero automatically.
> Oops. :-)

What about introducing functions like


inline int HV_EVTCHNOP_alloc_unbound(domid_t ldom,
               
                     domid_t
rdom,
               
                     U32
*port
               
                     )
{
        int err;
        evtchn_op_t op
= {
           
    .cmd = EVTCHNOP_alloc_unbound;
           
    .u.alloc_unbound.dom = ldom;
           
    .u.alloc_unbound.remote_dom = rdom;
           
    .u.alloc_unbound.port = *port;
        }
        err = HYPERVISOR_event_channel_op(&op);
        *port = op.u.alloc_unbound.port;
        return err;
}

to hide the specifics of the structure that needs
to be filled out and provide a form of parameter safety by forcing the
caller to pass all necessary paramers.

  Stefan
> 
>   -- Keir
> 
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