Re: [Xen-devel] [PATCH 06/12 v3] xen/arm: vpl011: Add a new vuart node in the xenstore

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, May 12, 2017 at 03:02:29PM +0530, Bhupinder Thakur wrote:
[...]
> >> @@ -151,13 +154,19 @@ retry_transaction:
> >>      if (rc) goto out;
> >>
> >>      if (!libxl_only) {
> >> -        rc = libxl__xs_write_checked(gc, t, 
> >> GCSPRINTF("%s/frontend",libxl_path),
> >> -                                     frontend_path);
> >> -        if (rc) goto out;
> >> +        if (fents || ro_fents)
> >> +        {
> >> +            rc = libxl__xs_write_checked(gc, t, 
> >> GCSPRINTF("%s/frontend",libxl_path),
> >> +                                         frontend_path);
> >> +            if (rc) goto out;
> >> +        }
> >>
> >> -        rc = libxl__xs_write_checked(gc, t, 
> >> GCSPRINTF("%s/backend",libxl_path),
> >> -                                     backend_path);
> >> -        if (rc) goto out;
> >> +        if (bents)
> >> +        {
> >> +            rc = libxl__xs_write_checked(gc, t, 
> >> GCSPRINTF("%s/backend",libxl_path),
> >> +                                         backend_path);
> >> +            if (rc) goto out;
> >> +        }
> >
> > What is this for?
> >
> > If there is no fe or be entries you skip the path creation altogether.
> > But why? This doesn't seem to be related to your patch.
> For vuart, I am adding only a front end node but the
> libxl__device_generic_add() creates the backend path also,even though
> there is no backend node. To remove that hanging be path, I added this
> check.
> >
> > At least explain this a bit in the commit message?
> I will add more details in the commit message.
> 

Preferable it should be in a separate patch. That would make review
easier.

But there is another question: how do you know if Dom0 is servicing a
DomU? How do you construct a libxl__device struct should you want to
manipulate vuart?

Wei.

> Regards,
> Bhupinder

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