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

[Roger Pau Monnà <roger.pau@xxxxxxxxxx>]

On 26/09/13 12:15, Ian Campbell wrote:
> 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?

Yes, we can move it with some modifications to the hotplug scripts, but
we will still need to create a directory like /libxl/<domid>/, or
something similar where the guest has write permissions, but I don't see
how this is any better than /local/domain/<domid>/libxl/.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel