[PATCH] ioemu: Get guest uuid from xenstore

[PATCH] ioemu: Get guest uuid from xenstore

[Yosuke Iwamatsu]

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xenstore_get_guess_uuid() retrieves the guest uuid by using a sysctl
hypercall through libxc now, but when we use the ioemu-stubdom, the
hcall is not allowed to be invoked.
This patch makes ioemu get the guest uuid from xenstore, instead of
using libxc.

Regards,
-----------------------
Yosuke Iwamatsu
        NEC Corporation

Signed-off-by: Yosuke Iwamatsu <y-iwamatsu@ab.jp.nec.com>



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Re: [PATCH] ioemu: Get guest uuid from xenstore

[Ian Jackson]

Yosuke Iwamatsu writes ("[Xen-devel] [PATCH] ioemu: Get guest uuid from xenstore"):
> xenstore_get_guess_uuid() retrieves the guest uuid by using a sysctl
> hypercall through libxc now, but when we use the ioemu-stubdom, the
> hcall is not allowed to be invoked.
> This patch makes ioemu get the guest uuid from xenstore, instead of
> using libxc.

I don't think this patch is safe.  /local/domain/<domid>/vm is
owned by (and thus writeable by) the domain in question.  We need a
trustworthy copy of this information.

Ian.

Re: [PATCH] ioemu: Get guest uuid from xenstore

[Keir Fraser]

On 19/01/2009 18:02, "Ian Jackson" <Ian.Jackson@eu.citrix.com> wrote:

> I don't think this patch is safe.  /local/domain/<domid>/vm is
> owned by (and thus writeable by) the domain in question.  We need a
> trustworthy copy of this information.

Perhaps worth checking with a xenstore-ls -p, or a xenstore-write attempt
within a domU, but the vm node should be owned by dom0 and read-only by the
domU. The recent xenstore permissions fixes should ensure that.

So the patch should be safe and if it's not it's a xend bug that needs
fixing.

 -- Keir

[PATCH] ioemu: Get guest uuid from xenstore

[Yosuke Iwamatsu]

Keir Fraser wrote:
> On 19/01/2009 18:02, "Ian Jackson" <Ian.Jackson@eu.citrix.com> wrote:
> 
>> I don't think this patch is safe.  /local/domain/<domid>/vm is
>> owned by (and thus writeable by) the domain in question.  We need a
>> trustworthy copy of this information.
> 
> Perhaps worth checking with a xenstore-ls -p, or a xenstore-write attempt
> within a domU, but the vm node should be owned by dom0 and read-only by the
> domU. The recent xenstore permissions fixes should ensure that.
> 
> So the patch should be safe and if it's not it's a xend bug that needs
> fixing.

I checked with 'xenstore-ls -p' on my system and could confirm that
the permission of /local/domain/<domid>/vm was set properly
(owned by dom0 and set read-only by domU), apparently since cs 18933.

Thanks,
   Yosuke

Re: [PATCH] ioemu: Get guest uuid from xenstore

[Ian Jackson]

Yosuke Iwamatsu writes ("[Xen-devel] [PATCH] ioemu: Get guest uuid from xenstore"):
> Keir Fraser wrote:
> > Perhaps worth checking with a xenstore-ls -p, or a xenstore-write attempt
> > within a domU, but the vm node should be owned by dom0 and read-only by the
> > domU. The recent xenstore permissions fixes should ensure that.

I looked with  xenstore-ls -p  but perhaps my test box is out of date.
I'll update it and see what it does then ...

Ian.

[PATCH] ioemu: Get guest uuid from xenstore

[Yosuke Iwamatsu]

Ian Jackson wrote:
> Yosuke Iwamatsu writes ("[Xen-devel] [PATCH] ioemu: Get guest uuid from xenstore"):
>> Keir Fraser wrote:
>>> Perhaps worth checking with a xenstore-ls -p, or a xenstore-write attempt
>>> within a domU, but the vm node should be owned by dom0 and read-only by the
>>> domU. The recent xenstore permissions fixes should ensure that.
> 
> I looked with  xenstore-ls -p  but perhaps my test box is out of date.
> I'll update it and see what it does then ...
> 

Any progress on this?
Please note that there is a real problem with the current implementation
(xenstore_get_guest_uuid() returns NULL in stub-dom mode) that sometime
the ioemu-domain crashes while running a Linux HVM domain, So we should
fix it somehow.

Thank you,
   Yosuke

Re: [PATCH] ioemu: Get guest uuid from xenstore

[Ian Jackson]

Yosuke Iwamatsu writes ("[Xen-devel] [PATCH] ioemu: Get guest uuid from xenstore"):
> Ian Jackson wrote:
> > I looked with  xenstore-ls -p  but perhaps my test box is out of date.
> > I'll update it and see what it does then ...

... what it did was break utterly and after I'd fixed it I'm afraid I
forgot about your patch.  I've checked now and it's fine so I have
applied your patch.

Thanks for the reminder.

Ian.