Re: [PATCH v2 02/10] libxl: create a local xenstore libxl and device-model dir for guests

["Roger Pau Monné" <roger.pau@citrix.com>]

On 11/11/13 16:24, Ian Jackson wrote:
> Roger Pau Monne writes ("[PATCH v2 02/10] libxl: create a local xenstore libxl and device-model dir for guests"):
>> 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. This also applies to Qemu which needs a
>> /local/<domid>/device-model xenstore directory.
>>
>> This patch creates the mentioned directories for each guest launched
>> from libxl.
> ...
>> diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
>> index d2d8921..d260895 100644
>> --- a/docs/man/xl.cfg.pod.5
>> +++ b/docs/man/xl.cfg.pod.5
>> @@ -307,6 +307,11 @@ which are incompatible with migration. Currently this is limited to
>>  enabling the invariant TSC feature flag in cpuid results when TSC is
>>  not emulated.
>>  
>> +=item B<driver_domain=BOOLEAN>
>> +
>> +Specify that this domain is a driver domain. This enables certain
>> +features needed in order to run a driver domain.
>> +
> 
> "Certain features" is a bit vague.  The definition of "driver domain"
> could be expaneded perhaps.  At the very least the manpage should
> explain whether a domain gets additional capabilities as a result of
> this option.  You should also say why not to set it always.

"Certain features" means two writeable xenstore paths inside of the
guest local path. IanC felt that it was best to set this as an option,
but I don't see any problem with enabling it for all guests (the guest
can already write to some local xenstore paths).

I've written this as a vague description because I don't know if we
might wish to expand this further at some point in the future.

> Is it the case that setting this option allows a guest to pretend to
> have backends for other guests ?

A guest can not pretend to have backends for other guests unless the
control domain writes the appropriate backend path inside of the guest,
this has not changed with this path.