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





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@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.)

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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