Re: about fully UMIP support in Xen

[Yu Zhang <yu.c.zhang@linux.intel.com>]

On 4/19/2017 10:09 PM, Andrew Cooper wrote:
> On 19/04/17 15:07, Jan Beulich wrote:
>>>>> On 19.04.17 at 15:58, <andrew.cooper3@citrix.com> wrote:
>>> On 19/04/17 14:50, Yu Zhang wrote:
>>>> On 4/19/2017 9:34 PM, Jan Beulich wrote:
>>>>>>>> On 19.04.17 at 13:44, <yu.c.zhang@linux.intel.com> wrote:
>>>>>> On 4/19/2017 7:19 PM, Jan Beulich wrote:
>>>>>>>>>> On 19.04.17 at 11:48, <yu.c.zhang@linux.intel.com> wrote:
>>>>>>>> Does hypervisor need to differentiate dom0 kernel and its
>>>>>>>> user space?
>>>>>>> If we want to para-virtualize the feature, then yes. Otherwise
>>>>>>> we can't assume the guest kernel would deal with user mode faults,
>>>>>>> so we'd have to. Arguably there could be a non-default mode in
>>>>>>> which we don't (forcing such applications to get a signal or crash).
>>>>>> For UMIP is to be para-virtualized,  is it OK to give dom0 kernel the
>>>>>> physical value
>>>>>> if instructions are triggered in the kernel?
>>>>> Why would you want to special case Dom0 here? I don't see
>>>>> anything wrong with giving Dom0 the real values, but since you'll
>>>>> have to not give DomU-s the real values, you'd then add more
>>>>> code to treat Dom0 specially. Simply give everyone fake values.
>>>> Oh. So in such case should return 0 to the dom0 kernel I guess?
>>>>
>>>> Here come a dumb question: does other pv domain also run in ring 3 in
>>>> vmx root mode,
>>>> or simply in vmx non-root ring 0?  :)
>>> PV guests execute exclusively in non-root mode.
>> In root mode, you mean.
> I do.  (oops.  Sorry.)

Thanks a lot, Andrew & Jan.
And back to the schedule of this feature, are you working on it? Or any 
specific plan?
Is there anything we can do here in Intel?

B.R.
Yu


> ~Andrew
>
>> Jan
>>
>>> 32bit PV guest kernels execute in ring 1.
>>> 64bit PV guest kernels execute in ring 3.
>>>
>>> ~Andrew
>>
>


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