Re: Nested virtualization on Intel does not work - second level freezes when third level is starting

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On Wed, Apr 11, 2012, Guido Winkelmann wrote about "Nested virtualization on Intel does not work - second level freezes when third level is starting":
> Nested virtualization on Intel does not work for me with qemu-kvm. As soon as 
> the third layer OS (second virtualised) is starting the Linux kernel, the 
> entire second layer freezes up. The last thing I can see console of the third 

Hi,

>From your description, I understand that "ordinary" (2-level) nested
virtualization working for you (host, guest and 2nd-level guest), and it's
the third nesting level (guest's guest's guest) which is broken?

This is the second report of this nature in a week (see the previous
report in https://bugzilla.kernel.org/show_bug.cgi?id=43068 - the
details there are different), so I guess I'll need to find the time
to give this issue some attention. L3 did work for me when the nested
VMX patches were included in KVM, so either something broke since, or
(perhaps more likely) your slightly different setups have features that
my setup didn't.

But in any case, like I explain in the aforementioned URL, even if L3 would
work, in the current implementation it would be extremenly slow - perhaps to
the point of being unusable (I think you saw this with grub performance in L3).
So I wonder if you'd really want to use it, even if it worked... Just
curious, what were you thinking of doing with L3?

Nadav.


-- 
Nadav Har'El                        |                 Wednesday, Apr 11 2012, 
nyh@xxxxxxxxxxxxxxxxxxx             |-----------------------------------------
Phone +972-523-790466, ICQ 13349191 |If I were two-faced, would I be wearing
http://nadav.harel.org.il           |this one?.... Abraham Lincoln
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