Re: [Xen-devel] [PATCH] Prevent xl save from segfaulting when control/shutdown key is removed

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Ian Campbell
> Sent: 23 November 2011 11:24
> To: Paul Durrant
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] [PATCH] Prevent xl save from segfaulting
> when control/shutdown key is removed
> 
> On Wed, 2011-11-23 at 11:19 +0000, Paul Durrant wrote:
> > what is the reason for creating control ro to the guest?
> 
> In general libxl prefers to whitelist paths which the guest can
> write too, just to prevent a complete free for all, keep things
> somewhat under control and to help avoid situations where tools
> might inadvertently rely on a guest-writeable key in an unsafe way..
> 
> >  In XenServer we allow the guest to write the control key to
> advertise
> > feature-shutdown, feature-suspend etc. so that the tools know what
> > values of control/shutdown the guest will respond to.
> 
> The libxl way would be to create these at build time (perhaps empty)
> with the appropriate permissions.
> 
> It's not clear how that functionality can be added in a way which is
> compatible with existing guests though, e.g. no Linux guest writes
> those but many can be suspended etc.
> 

So the simple solution, for compatibility's sake, is to make control rw isn't 
it?

  Paul
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