Re: [Xen-devel] [PATCH 09/24] xen/arm: compile and run xenbus

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 1 Aug 2012, Konrad Rzeszutek Wilk wrote:
> On Thu, Jul 26, 2012 at 04:33:51PM +0100, Stefano Stabellini wrote:
> > bind_evtchn_to_irqhandler can legitimately return 0 (irq 0): it is not
> > an error.
> > 
> > If Linux is running as an HVM domain and is running as Dom0, use
> > xenstored_local_init to initialize the xenstore page and event channel.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > ---
> >  drivers/xen/xenbus/xenbus_comms.c |    2 +-
> >  drivers/xen/xenbus/xenbus_probe.c |   27 +++++++++++++++++----------
> >  drivers/xen/xenbus/xenbus_xs.c    |    1 +
> >  3 files changed, 19 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/xen/xenbus/xenbus_comms.c 
> > b/drivers/xen/xenbus/xenbus_comms.c
> > index 52fe7ad..c5aa55c 100644
> > --- a/drivers/xen/xenbus/xenbus_comms.c
> > +++ b/drivers/xen/xenbus/xenbus_comms.c
> > @@ -224,7 +224,7 @@ int xb_init_comms(void)
> >             int err;
> >             err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
> >                                             0, "xenbus", &xb_waitq);
> > -           if (err <= 0) {
> > +           if (err < 0) {
> >                     printk(KERN_ERR "XENBUS request irq failed %i\n", err);
> >                     return err;
> >             }
> > diff --git a/drivers/xen/xenbus/xenbus_probe.c 
> > b/drivers/xen/xenbus/xenbus_probe.c
> > index b793723..3ae47c2 100644
> > --- a/drivers/xen/xenbus/xenbus_probe.c
> > +++ b/drivers/xen/xenbus/xenbus_probe.c
> > @@ -729,16 +729,23 @@ static int __init xenbus_init(void)
> >     xenbus_ring_ops_init();
> >  
> >     if (xen_hvm_domain()) {
> > -           uint64_t v = 0;
> > -           err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
> > -           if (err)
> > -                   goto out_error;
> > -           xen_store_evtchn = (int)v;
> > -           err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
> > -           if (err)
> > -                   goto out_error;
> > -           xen_store_mfn = (unsigned long)v;
> > -           xen_store_interface = ioremap(xen_store_mfn << PAGE_SHIFT, 
> > PAGE_SIZE);
> > +           if (xen_initial_domain()) {
> > +                   err = xenstored_local_init();
> > +                   xen_store_interface =
> > +                           phys_to_virt(xen_store_mfn << PAGE_SHIFT);
> > +           } else {
> > +                   uint64_t v = 0;
> > +                   err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
> > +                   if (err)
> > +                           goto out_error;
> > +                   xen_store_evtchn = (int)v;
> > +                   err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
> > +                   if (err)
> > +                           goto out_error;
> > +                   xen_store_mfn = (unsigned long)v;
> > +                   xen_store_interface =
> > +                           ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
> > +           }
> 
> This, and along with the Hybrid PV dom0 (not yet posted, but it was doing
> similar manipulation here) is getting more and more like a rat-mess.
> 
> 
> Any chance we can just abstract the three different XenStore access
> ways and just have something like this:
> 
>       enum {
>               USE_UNKNOWN
>               USE_HVM,
>               USE_PV,
>               USE_LOCAL
>               USE_ALREADY_INIT
>       };
>       int usage = USE_UNKNOWN;
>       if (xen_pv_domain())
>               usage = USE_PV;
>       if (xen_hvm_domain())
>               usage = USE_HVM;
>       if (xen_initial_domain())
>               usage = USE_LOCAL;
> 
>       if (xen_start_info->store_evtchn)
>               usage = USE_ALREADY_INIT;
>       
>       .. other overwrites..
> 
>       switch (usage) {
>               .. blah blah.
>       }

I'll give it a try.

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