Re: event notification

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Mar 11, 2010 at 07:43:00AM +0000, Ian Campbell wrote:
> On Wed, 2010-03-10 at 23:20 +0000, ravi kerur wrote:
> > Thanks Ian and Konrad. I thought monitoring udev events or xen store
> > watch can be done from user-level apps. I am wondering can they be
> > used from kernel modules as well?
> 
> xenstore can. I don't think udev can.

<nods>

Of interest might be git commit dfecff0a8934996f381cb5a80c7220ad87830ae9
"commit dfecff0a8934996f381cb5a80c7220ad87830ae9
Author: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date:   Thu Nov 5 15:25:40 2009 -0500

    xenbus_walk - walk XenStore keys, calling callback.
    
    This is quite similar to 'pci_walk_bus.' We walk the
    XenStore keys, starting at the initial path, calling the
    callback with each key that has a value. If the callback
    returns a negative value we stop, clean up, and return the
    value back.
    
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
"
which you could use to get more details of your XenStore values.

(this commit is in Jeremy's Xen tree
git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git)
> 
> Ian.
> 
> > 
> > Thanks
> > -RK
> > 
> > On Wed, Mar 10, 2010 at 8:09 AM, Ian Campbell
> > <Ian.Campbell@citrix.com> wrote:
> >         On Mon, 2010-03-08 at 16:47 +0000, Konrad Rzeszutek Wilk
> >         wrote:
> >         > On Sat, Mar 06, 2010 at 07:12:02PM -0800, ravi kerur wrote:
> >         > > Hi,
> >         > >
> >         > > Is there a mechanism available in Xen such that a kernel
> >         module in dom0 can
> >         > > register to it and when a VM(domU) is installed or deleted
> >         or suspend or
> >         > > resumed kernel module in domU can send notification to its
> >         counterpart in
> >         > > dom0. I have looked into xenbus mechanism used by PV
> >         drivers and it won't
> >         > > work for us. Inputs appreciated.
> >         >
> >         > You can listen on udev events and see when a vif device has
> >         been added.
> >         > Also you can add pieces to the dom0 kernel to send uevents
> >         when a device
> >         > is suspended and do something.
> >         >
> >         > Attached is a simple program to listen to all uevents..
> >         
> >         
> >         Also if you are specifically interested in domain
> >         create/destruction
> >         (from the hypervisors PoV) then I think you can add a xenstore
> >         watch on
> >         "@releaseDomain" and "@introduceDomain".
> >         
> >         As far as the hypervisor is concerned things like migration or
> >         suspend/resume are just domain creation or destruction, the
> >         "illusion"
> >         of anything more is provided by the tools.
> >         
> >         If you are interested in the creation/suspension/migration/etc
> >         of
> >         domains at the toolstack level then it depends which toolstack
> >         you are
> >         targeting.
> >         
> >         
> > 
> 
> 
> 
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