Re: about fully UMIP support in Xen

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

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?  :)

Thanks
Yu

>> And if the instructions are triggered in dom0 user space, the spec
>> requires a #GP
>> fault, and we can return 0 to the application in the #GP fault handler,
>> is it OK?
> Yes, I think so. But the fundamental rule is - make it match what
> native Linux does in that case.
>
> Jan
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> https://lists.xen.org/xen-devel


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