Xen devel - Jan 2009 - Problem with starting guest (para_virt dom0)

Hi,

I''ve managed to get a para_virt dom0 running on my x86_64 system but
having
problems starting a guest.  First problem was that xenstore client programs
weren''t able to communicate over xenbus (xs_write_all hitting its
return
false branch) still not sure why this is happening. I was able to at least
get xenstore working by hacking the client to use the normal socket by
default.

But now I''m getting:
Error: [Errno 2] No such file or directory:
''/proc/xen/balloon''

Google only turned up reports that this is related to trying to give the
guest too much memory, but xm info shows I have over 3.5G free and only
trying to give 128M to the guest. Any other ideas what might be causing
this?

Thanks,

Adam
Adam Wendt Consulting


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On Wed, 2009-01-14 at 23:56 -0800, Adam Wendt wrote:
> Hi,
> 
> I''ve managed to get a para_virt dom0 running on my x86_64 system
but
> having problems starting a guest.  First problem was that xenstore
> client programs weren''t able to communicate over xenbus
(xs_write_all
> hitting its return false branch) still not sure why this is happening.
> I was able to at least get xenstore working by hacking the client to
> use the normal socket by default.
Perhaps you need to enable xenfs in your kernel build and mount it
on /proc/xen in order to gain access to /proc/xen/xsd*?
> But now I''m getting:
> Error: [Errno 2] No such file or directory:
''/proc/xen/balloon''
> 
> Google only turned up reports that this is related to trying to give
> the guest too much memory, but xm info shows I have over 3.5G free and
> only trying to give 128M to the guest. Any other ideas what might be
> causing this?
pvops only supports balloon via a sysfs interface not proc. There is a
patch in xen-unstable.hg from Jeremy Fitzhardinge which fixes this but
you''ll either need to use xen-unstable or backport it to whatever you
are using (it''s pretty simple, IIRC).

Ian.



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On Thu, Jan 15, 2009 at 12:04 AM, Ian Campbell
<Ian.Campbell@citrix.com>wrote:
> On Wed, 2009-01-14 at 23:56 -0800, Adam Wendt wrote:
> > Hi,
> >
> > I''ve managed to get a para_virt dom0 running on my x86_64
system but
> > having problems starting a guest.  First problem was that xenstore
> > client programs weren''t able to communicate over xenbus
(xs_write_all
> > hitting its return false branch) still not sure why this is happening.
> > I was able to at least get xenstore working by hacking the client to
> > use the normal socket by default.
>
> Perhaps you need to enable xenfs in your kernel build and mount it
> on /proc/xen in order to gain access to /proc/xen/xsd*?

Not sure if you actually meant /proc/xen/xsd or that was just a mistype, but
xs_lib.c tries to use /proc/xen/xenbus which _does_ exist in /proc/xen/ but
like I said above the xs_write_all hits the return false branch so something
wrong with the filehandle or who knows what, for now I was able to get
rudimentary xenstore functionality working defaulting to the socket
interface, but when I try to start a guest I get a bunch of:

xenstore-write: could not write path backend/vbd/1/770/hotplug-error
xenstore-write: could not write path backend/vbd/1/771/hotplug-error
xenstore-write: could not write path backend/vbd/1/770/hotplug-error

In the hotplug log and then guest creation errors out about failed hotplug.
So still unable to start a guest.
>
>
> > But now I''m getting:
> > Error: [Errno 2] No such file or directory:
''/proc/xen/balloon''
> >
> > Google only turned up reports that this is related to trying to give
> > the guest too much memory, but xm info shows I have over 3.5G free and
> > only trying to give 128M to the guest. Any other ideas what might be
> > causing this?
>
> pvops only supports balloon via a sysfs interface not proc. There is a
> patch in xen-unstable.hg from Jeremy Fitzhardinge which fixes this but
> you''ll either need to use xen-unstable or backport it to whatever
you
> are using (it''s pretty simple, IIRC).
>
Ok yea I switched back to xen-unstable for now, though not sure if unstable
is causing my above xenstore-write error as I wasn''t getting that on
3.3.1
(but was then getting the balloon error)

Adam
>
> Ian.
>
>
>

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