Re: [Xen-devel] about fully UMIP support in Xen

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 19/04/17 15:07, Jan Beulich wrote:
>>>> On 19.04.17 at 15:58, <andrew.cooper3@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx> wrote:
>>>>> On 4/19/2017 7:19 PM, Jan Beulich wrote:
>>>>>>>>> On 19.04.17 at 11:48, <yu.c.zhang@xxxxxxxxxxxxxxx> 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.)

~Andrew

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


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