Re: [Xen-devel] [PATCH (V9) 2/2] xen: Add V4V implementation

[Ross Philipson <ross.philipson@xxxxxxxxxx>]

On 05/28/2013 08:43 PM, Matt Wilson wrote:
> On Tue, May 28, 2013 at 03:43:31PM -0400, Ross Philipson wrote:
> > Setup of v4v domains a domain gets created and cleanup
> > when a domain die. Wire up the v4v hypercall.
> >
> > Include v4v internal and public headers.
> >
> > Signed-off-by: Ross Philipson<ross.philipson@xxxxxxxxxx>
> Would you consider making a boot-time option to disable v4v entirely?
I think that sounds reasonable since if you are not using it, it is 
consuming resources needlessly. I actually was thinking about this 
yesterday shortly after submitting the last patch set.
Thanks
Ross

> > --- a/xen/common/domain.c
> > +++ b/xen/common/domain.c
> > @@ -199,7 +199,8 @@ struct domain *domain_create(
> >   {
> >       struct domain *d, **pd;
> >       enum { INIT_xsm = 1u<<0, INIT_watchdog = 1u<<1, INIT_rangeset = 1u<<2,
> > -           INIT_evtchn = 1u<<3, INIT_gnttab = 1u<<4, INIT_arch = 1u<<5 };
> > +           INIT_evtchn = 1u<<3, INIT_gnttab = 1u<<4, INIT_arch = 1u<<5,
> > +           INIT_v4v = 1u<<6 };
> >       int err, init_status = 0;
> >       int poolid = CPUPOOLID_NONE;
> >
> > @@ -312,6 +313,13 @@ struct domain *domain_create(
> >           spin_unlock(&domlist_update_lock);
> >       }
> Perhaps an opt_v4v check here?
>
> > +    if ( !is_idle_domain(d) )
> > +    {
> > +        if ( (err = v4v_init(d)) != 0 )
> > +            goto fail;
> > +        init_status |= INIT_v4v;
> > +    }
> > +
> >       return d;
> >
> >    fail:
> [...]
>
> > new file mode 100644
> > index 0000000..701877d
> > --- /dev/null
> > +++ b/xen/common/v4v.c
> [...]
>
> > +/*
> > + * hypercall glue
> > + */
> > +long
> > +do_v4v_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg1,
> > +          XEN_GUEST_HANDLE_PARAM(void) arg2,
> > +          uint32_t arg3, uint32_t arg4)
> > +{
> > +    struct domain *d = current->domain;
> > +    long rc = -EFAULT;
> > +
> > +    v4v_dprintk("->do_v4v_op(%d,%p,%p,%d,%d)\n", cmd,
> > +                (void *)arg1.p, (void *)arg2.p, (int) arg3, (int) arg4);
> > +
> and check for d->v4v != NULL here, bailing with -ENOSYS?
>
> > +    domain_lock(d);
> > +    switch (cmd)
> > +    {
> > +    case V4VOP_register_ring:
> [...]
>
> --msw

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