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

[Nadav Har'El <nyh@math.technion.ac.il>]

On Wed, Apr 11, 2012, Guido Winkelmann wrote about "Re: Nested virtualization on Intel does not work - second level freezes when third level is starting":
> No, even 2-level nesting is broken. I can run Host->Guest, but not 
> Host->Guest->2nd Level Guest. I haven't even tried with a third virtualized 
> level.

I see. I guess I completely misunderstood what you reported. Sorry.

I think Orit was right. 3.3rc5 had a regression in the nested support,
which I discovered and Avi Kivity fixed; I didn't notice this before
now, but unfortunately the fix only got to 3.4rc1 and never made it into
3.3 (I just verified, it's not in 3.3.1 but it is in 3.4).
This bug displayed itself similarly to what you saw (L1 would hang when
running L2).

If you can run a later kernel, I hope the problem will be solved.

Otherwise, perhaps you can patch your kernel with the following patch
and try again?

--- .before/arch/x86/kvm/vmx.c  2012-03-19 18:34:24.000000000 +0200
+++ .after/arch/x86/kvm/vmx.c   2012-03-19 18:34:24.000000000 +0200
@@ -2210,6 +2210,10 @@ static int vmx_set_msr(struct kvm_vcpu *
                msr = find_msr_entry(vmx, msr_index);
                if (msr) {
                        msr->data = data;
+                       if (msr - vmx->guest_msrs < vmx->save_nmsrs)
+                               kvm_set_shared_msr(msr->index, msr->data,
+                                       msr->mask);
                        break;
                }



-- 
Nadav Har'El                        |                  Thursday, Apr 12 2012, 
nyh@math.technion.ac.il             |-----------------------------------------
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