Re: [Xen-devel] libvchan-error

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 05/07/2013 11:43 PM, Shakeel Butt wrote:
> On Fri, May 3, 2013 at 7:23 AM, Khandelwal, Shubham
> <Shubham.Khandelwal@xxxxxxxxxx> wrote:
> > Hi,
> >
> >
> >
> > I am trying to use the libvchan tool for Inter domain communication for
> > XEN-ARM on Fast Model for VExpress platform. I have successfully compiled it
> > and ported the following in the rootfs :
> >
> > libxenvchan.so, libxenvchan.so.1.0, libxenvchan.so.1.0.0, libxenvchan.a,
> > vchan-node1, vchan-node2.
> >
> >
> >
> > But when I am using it shows the following error in both dom0 and domU.
> >
> > …
> >
> > # vchan-node1 server read 1 1536
> >
> > libxenvchan_*_init: No such file or directory
> >
> > …
> >
> >
> >
> > Am I missing some files here ?
> Are you running the server in Dom0? If yes then check “xenstore-read
> /local/domain/0/domid”, if nothing is there, write 0 to it.
>
> The server side of libvchan reads its id from xenstore and use it to
> remove its permission over the nodepath. Not sure why? (CCed to
> Daniel, any particular reason)
It does not remove its own permission; instead, it sets itself as the
owner for the nodes when changing permissions. Element 0 in a xenstore
permission list describes owner for the domid and "other" for the r/w
bits, a common source of confusion.

Reading the "domid" node was the simplest way for a domain to determine
its own domid, which is required to do this.  If dom0 commonly does not
have this node, it may be preferable to switch to making a get-permission
call on the node you just created instead, and assume that you are the
owner of that node.

> > Regards
> >
> >
> >
> > Shubham Khandelwal

--
Daniel De Graaf
National Security Agency

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