Opteron AMD-V support

Opteron AMD-V support

[Govender, Sashan]

Hi

We bumped into this issue with VMWare ESX 4 where it doesn't support hardware virtualization if the processor is an AMD Athlon/Opteron (http://communities.vmware.com/docs/DOC-9150). Does linux-kvm have a similar issue? More specifically will the the module kvm_amd.ko support AMD-V on an Opteron 2218?

Thanks

Re: Opteron AMD-V support

[Brian Jackson]

On Thursday 03 June 2010 21:33:24 Govender, Sashan wrote:
> Hi
> 
> We bumped into this issue with VMWare ESX 4 where it doesn't support
> hardware virtualization if the processor is an AMD Athlon/Opteron
> (http://communities.vmware.com/docs/DOC-9150). Does linux-kvm have a
> similar issue? More specifically will the the module kvm_amd.ko support
> AMD-V on an Opteron 2218?


Yes, KVM doesn't try to be too smart. If you have svm/vt, it runs. If you 
don't, it falls back to tcg (qemu's normal/slow mode). The kvm-amd module will 
load as long as the bios and the CPU both support and enable svm.


> 
> Thanks
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Re: Opteron AMD-V support

[Andre Przywara]

Brian Jackson wrote:
> On Thursday 03 June 2010 21:33:24 Govender, Sashan wrote:
>> Hi
>>
>> We bumped into this issue with VMWare ESX 4 where it doesn't support
>> hardware virtualization if the processor is an AMD Athlon/Opteron
>> (http://communities.vmware.com/docs/DOC-9150). Does linux-kvm have a
>> similar issue? More specifically will the the module kvm_amd.ko support
>> AMD-V on an Opteron 2218?

> Yes, KVM doesn't try to be too smart. If you have svm/vt, it runs. If you 
> don't, it falls back to tcg (qemu's normal/slow mode). The kvm-amd module will 
> load as long as the bios and the CPU both support and enable svm.

That's right. Please note that KVM depends on hardware virtualization, 
so it does not have the choice like VMware has. Falling back to QEMU/TCG 
is not comparable to VMware's binary translation, because their approach 
is highly optimized and limited to x86 on x86, whereas QEMU wants to 
emulate each supported architecture on each host architecture, so it 
naturally cannot be as sophisticated as the VMware approach.
Nested paging has been supported by KVM for a long time, if it's there 
it will be automatically used.

BTW, every Opteron with a four-digit number supports AMD-V, and KVM will 
run on every such processor. I am not aware of any _Opteron_ boards not 
allowing AMD-V, but there are some desktop/notebook systems where the 
BIOS denies AMD-V (although the processor has it).
There presence of the "svm" flag in /proc/cpuinfo is a safe indicator 
for the usability of KVM.

Regards,
Andre.


-- 
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448-3567-12