Re: [Xen-devel] [PATCH v12 for-xen-4.5 01/20] common/symbols: Export hypervisor symbols to privileged guest

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.09.14 at 16:16, <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 09/29/2014 09:47 AM, Jan Beulich wrote:
>>>>> On 29.09.14 at 15:29, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> I am not sure I understand how setting fields to zero would help with
>>> figuring out whether a new fields has been added. I can see how it can
>>> in some cases but not in general.
>> If you check that padding fields are zero now, meaning can be
>> assigned to them later on, while if you allow them to be uninitialized,
>> that's not an option.
> 
> What if the new field is meant to be zero? You can't guarantee that if 
> pad is zero it is still a pad on the "other side" of the call, can you?

I don't understand what you trying to tell me here.

> Besides, in this particular case, the structure is set up in the caller, 
> so presumably it should be the one clearing all pads (which it does, but 
> not for this specific reason).

Of course it's the caller to zero the field. And the callee (hypervisor)
to check that it's zero. I never said the hypervisor should clear it.

Jan


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