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Re: [Xen-devel] [PATCH] Prevent xl save from segfaulting when control/shutdown key is removed
On Wed, 2011-11-23 at 12:59 +0000, Paul Durrant wrote:
> > -----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
The problem I'm thinking of exists even if control is rw.
Given an empty control directory how do you know if a guest supports
suspend or not, given that most existing guests which do support suspend
do not write any key there?
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