Re: [Qemu-devel] nested VMX with IA32_FEATURE_CONTROL MSR(addr: 0x3a) value of ZERO

[Jan Kiszka]

On 2015-01-13 14:43, Paolo Bonzini wrote:
> 
> 
> On 13/01/2015 14:19, Huaicheng Li wrote:
>> Hi, all
>>
>> I have a Linux 3.8 kernel (host) and run QEMU 1.5.3 on it. I want to
>> test another hypervisor software in qemu so I enabled KVM's nested VMX
>> function(by passing "nested=1" parameter to the kvm module) and then
>> started a guest machine. In the guest, I could see the "vmx" instruction
>> set by reading /proc/cpuinfo and the kvm module can be correctly
>> inserted. But when I read the value of the IA32_FEATURE_CONTROL MSR
>> using msr-tools, it showed _0_, but the correct value should be _5_,
>> since bit 0(virtualization lock bit) and bit 2 of that MSR must be set
>> to enable the virtualization functionality. But in my vmware workstation
>> guest with nested virtualization enabled, the value of that MSR is,
>> indeed, _5_ as well as in the physical machine (of course). Here, I want
>> to ask
>>
>> * Am I missing anything in my operation to totally enable the nested
>> virtualization function ?? (I googled a lot and it seemed there were no
>> additional steps) 
> 
> You have an old kernel.  IA32_FEATURE_CONTROL MSR emulation was added in
> 3.12.

...and lots of other nvmx bugs were fixed afterwards. If you don't want
to debug KVM but your hypervisor, use the latest stable kernel,
currently 3.18.2.

Jan

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