libvirt users - Feb 2018 - Re: Nested KVM: L0 guest produces kernel BUG on wakeup from managed save (while a nested VM is running)

On Thu, Feb 08, 2018 at 06:44:43PM +0100, Florian Haas
wrote:
> On Thu, Feb 8, 2018 at 1:07 PM, David Hildenbrand <david@redhat.com>
wrote:
> > We should certainly document what I have summaries here properly at a
> > central palce!
> 
> Please review the three edits I've submitted to the wiki:
> https://www.linux-kvm.org/page/Special:Contributions/Fghaas
> 
> Feel free to ruthlessly edit/roll back anything that is inaccurate.
> Thanks!
I've made some minor edits to clarify a bunch of bits, and a link to the
Kernel doc about Intel nVMX.  (Hope that looks fine.)

You wrote: "L2...which does no further virtualization".  Not quite
true
— "under right circumstances" (read: sufficiently huge machine with
tons
of RAM), L2 _can_ in turn L3. :-)

Last time I checked (this morning), Rich W.M. Jones had 4 levels of
nesting tested with the 'supernested' program[1] he wrote.  (Related
aside: This program is packaged it as part of 2016 QEMU Advent
Calendar[2] -- if you want to play around on a powerful test machine
with tons of free memory.)

[1] http://git.annexia.org/?p=supernested.git;a=blob;f=README
[2] http://www.qemu-advent-calendar.org/2016/#day-13

-- 
/kashyap

On Fri, Feb 9, 2018 at 11:48 AM, Kashyap Chamarthy <kchamart@redhat.com>
wrote:
> On Thu, Feb 08, 2018 at 06:44:43PM +0100, Florian Haas wrote:
>> On Thu, Feb 8, 2018 at 1:07 PM, David Hildenbrand
<david@redhat.com> wrote:
>> > We should certainly document what I have summaries here properly
at a
>> > central palce!
>>
>> Please review the three edits I've submitted to the wiki:
>> https://www.linux-kvm.org/page/Special:Contributions/Fghaas
>>
>> Feel free to ruthlessly edit/roll back anything that is inaccurate.
>> Thanks!
>
> I've made some minor edits to clarify a bunch of bits, and a link to
the
> Kernel doc about Intel nVMX.  (Hope that looks fine.)
I'm sure they it does, but just so you know I currently don't see any
edits from you on the Nested Guests page. Are you sure you
saved/published your changes?
> You wrote: "L2...which does no further virtualization".  Not
quite true
> — "under right circumstances" (read: sufficiently huge machine
with tons
> of RAM), L2 _can_ in turn L3. :-)
Insert "normally" between "which" and "does",
then. :)
> Last time I checked (this morning), Rich W.M. Jones had 4 levels of
> nesting tested with the 'supernested' program[1] he wrote. 
(Related
> aside: This program is packaged it as part of 2016 QEMU Advent
> Calendar[2] -- if you want to play around on a powerful test machine
> with tons of free memory.)
>
> [1] http://git.annexia.org/?p=supernested.git;a=blob;f=README
> [2] http://www.qemu-advent-calendar.org/2016/#day-13
Interesting, thanks for the pointer!

Cheers,
Florian

On Fri, Feb 09, 2018 at 12:02:25PM +0100, Florian Haas
wrote:
> On Fri, Feb 9, 2018 at 11:48 AM, Kashyap Chamarthy
<kchamart@redhat.com> wrote:
[...]
> > I've made some minor edits to clarify a bunch of bits, and a link
to the
> > Kernel doc about Intel nVMX.  (Hope that looks fine.)
> 
> I'm sure they it does, but just so you know I currently don't see
any
> edits from you on the Nested Guests page. Are you sure you
> saved/published your changes?
Thanks for catching that.  _Now_ it's updated.

    https://www.linux-kvm.org/page/Nested_Guests

(I also didn't have permissions to add external links; had to get that
sorted out with the admin.)
> > You wrote: "L2...which does no further virtualization".  Not
quite true
> > — "under right circumstances" (read: sufficiently huge
machine with tons
> > of RAM), L2 _can_ in turn L3. :-)
> 
> Insert "normally" between "which" and "does",
then. :)
:-)
> > Last time I checked (this morning), Rich W.M. Jones had 4 levels of
> > nesting tested with the 'supernested' program[1] he wrote. 
(Related
> > aside: This program is packaged it as part of 2016 QEMU Advent
> > Calendar[2] -- if you want to play around on a powerful test machine
> > with tons of free memory.)
> >
> > [1] http://git.annexia.org/?p=supernested.git;a=blob;f=README
> > [2] http://www.qemu-advent-calendar.org/2016/#day-13
> 
> Interesting, thanks for the pointer!
> 
> Cheers,
> Florian
-- 
/kashyap