nested virtualization: xen-on-xen

nested virtualization: xen-on-xen

[Christoph Egger]

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Hi Tim,

You report that you can boot Xen 4.0 on Xen-unstable but not
Xen 4.1 or Xen-unstable on Xen-unstable, right?

I suppose the problem is that the l1 Dom0 hangs at boot.

Attached patch fixes this problem for me. Please give
it a try.

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>


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diff -r b7e5a2566332 -r 28b49fc064ea tools/libxc/xc_cpuid_x86.c
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -320,7 +320,6 @@ static void xc_cpuid_hvm_policy(
                       bitmaskof(X86_FEATURE_XSAVE)) : 0));
 
         regs[2] |= (bitmaskof(X86_FEATURE_HYPERVISOR) |
-                    bitmaskof(X86_FEATURE_TSC_DEADLINE) |
                     bitmaskof(X86_FEATURE_X2APIC));
 
         regs[3] &= (bitmaskof(X86_FEATURE_FPU) |

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Re: nested virtualization: xen-on-xen

[Tim Deegan]

Hi,

At 11:35 +0200 on 01 Jul (1309520148), Christoph Egger wrote:
> You report that you can boot Xen 4.0 on Xen-unstable but not
> Xen 4.1 or Xen-unstable on Xen-unstable, right?

I have two firm datapoints: 32-bit 4.0 (as shipped in Debian Squeeze)
works OK; 64-bit xen-unstable with a 64-bit debian testing kernel fails.
I tried some other configurations but don't remember the details.

> I suppose the problem is that the l1 Dom0 hangs at boot.

The problem I saw was that during n1 dom0 boot the screen would go black
and the cpu usage hit 100%.  Sampling the vCPU state showed plausible
hypercalls being made and it didn't seem to be stuck in one particular
loop.  

> Attached patch fixes this problem for me. Please give it a try.

Thanks.  I tried this patch and it made no difference, though it's
possible that I slipped up somewhere installing the new libxc.

If I get time next week I'll dig into it further. 

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@citrix.com>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)