Re: [Xen-devel] [PATCH RFC 04/12] libxl: create a local xenstore libxl and device-model dir for guests

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-09-26 at 11:57 +0200, Roger Pau Monnà wrote:
> On 26/09/13 11:39, Ian Campbell wrote:
> > On Thu, 2013-09-26 at 11:27 +0200, Roger Pau Monnà wrote:
> >> On 25/09/13 15:48, Ian Campbell wrote:
> >>> On Mon, 2013-09-23 at 12:30 +0200, Roger Pau Monne wrote:
> >>>> If libxl is executed inside a guest domain it needs write access to
> >>>> the local libxl xenstore dir (/local/<domid>/libxl) to store internal
> >>>> data.
> >>>
> >>> These sorts of changes need a patch against docs/misc/xenstore-paths.txt
> >>> too.
> >>
> >> Ack.
> >>
> >>>
> >>>>  This also applies to Qemu which needs a
> >>>> /local/<domid>/device-model xenstore directory.
> >>>
> >>> Is this a new requirement or a separate preexisting issue? How have we
> >>> lived without it?
> >>
> >> This entry is so far only created on Dom0 (because it's the only domain
> >> that launches Qemu, and is created by Qemu if needed), but when running
> >> on a guest, the guest doesn't have permissions to write on
> >> /local/<domid>/, so we have to create the directory in the toolstack
> >> domain and assign write permissions for the guest.
> >>
> >> This path is hardcoded in Qemu, so it's quite difficult to change it,
> >> that's why I've opted for creating it on domain creation.
> > 
> > OK :-/
> > 
> >>>> This patch creates the mentioned directories for each guest launched
> >>>> from libxl.
> >>>
> >>> I don't really like leaking toolstack "internals" into the normal guest
> >>> namespace. Can we add an option to specify "this is a toolstack domain"
> >>> and key off that?
> >>
> >> OK, something like driver_domain=1|0
> > 
> > Something like that, yes.
> > 
> >>> I also wonder if this shouldn't be /libxl/<domid> at the top level.
> >>
> >> I don't have a strong opinion on this, but I generally prefer to keep
> >> all the xenstore related keys for a domain inside /libxl/<domid>.
> > 
> > Are you agreeing with me or did you mean /local/(domain/)<domid> ?
> 
> I would prefer to place it in /local/domain/<domid>/libxl/ because I get
> the feeling it's more contained, but frankly I don't have a strong
> opinion on this, if you prefer to use /libxl/<domid> I can go for it.
> 
> However keep in mind that we will have to create the
> /local/domain/<domid>/libxl dir anyway, because we have to write the
> hotplug disable key there (/local/domain/<domid>/libxl/disable_udev).

That's a toolstack "internal" key isn't it, which we can move? Or is it?



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