Re: Will KVM support "Xen on KVM" type in nested virtualization ?

[Avi Kivity <avi@redhat.com>]

On 08/11/2012 12:20 PM, Ren, Yongjie wrote:
> Hi folks,
> I did some basic testing on nested virtualization on Intel x86-64 platform.
> Will KVM support Xen as L1 guest in nested virtualization ?
> 
> When I tried "Xen on KVM" mode, I found VMX can't be initialized in L1 Xen hypervisor.
> I tried both "-cpu host" and "-cpu qemu64,+vmx" parameters in qemu-kvm command line.
> -------some log in 'xl dmesg' command line in L1 Xen ---
> (XEN) VMX: CPU0 has insufficent CPU-Based Exec Control (b299868c but requires min 2299968c)
> (XEN) VMX: CPU0 has insufficent VMExit Control (00000200 but requires min 00008200)
> (XEN) VMX: failed to initialise.
> ------more details in the attached "xl-dmesg-L1.log"----
> In Xen source code, I found the following related to the mentioned error.
> "xen-unstable.hg/xen/include/asm-x86/hvm/vmx/vmcs.h"
> #define CPU_BASED_RDTSC_EXITING               0x00001000
> #define VM_EXIT_ACK_INTR_ON_EXIT        0x00008000
> 
> Will KVM expose these two features in its vCPU ?

Those are two bugs in kvm.  The first is trivial to fix, the second is
harder.  I will take a look.


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