virtualbox.org

Hi,
Just installed VB OSE, but i does not work the way it should. In the session information on the basic tab it says VT-x/AMD-V are activated, but on the runtime it says it isn't and i'm sure it's not, it's _horrilbe_ slow. The kernel module is loaded:

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% lsmod|grep box
vboxnetadp              4193  0 
vboxnetflt             12525  1 
vboxdrv              1723671  5 vboxnetadp,vboxnetflt

My mainboard is supporting AMD-V and it workes well with QEMU/KVM, but these don't have have a good graphic performace, the sound is laggy and bridged networking is pain, so i tryed out VB. Do I have to unload any kvm modules? Where can i read error messages?

Sepp Mosh

QEMU/KVM

If these are still active on the host VirtualBox will not/can not use VT-x/AMD-v as it would corrupt everything. Make sure that KVM is completely stopped and try again.

Checking hardware assisted virtualization support in CPU

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egrep -q '^flags.*(vmx|svm)' /proc/cpuinfo && echo yes

If you don't get yes in output, then the answer is obviously no.

Checking whether hardware virtualization is enabled/used in AMD CPUs
Checking SVME bit (12th bit, counting from 0 as in AMD docs, SVM Enable) in EFER (MSR 0xC0000080, Extended Feature Enable Register).
You can check it using rdmsr from msr-tools package.

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sudo rdmsr 0xC0000080 #EFER

If you get a number where 4th (counting from 1 and obviously from right) hexadecimal digit has first bit set, or it just equals 1, then SVME is on.

If you've got an error, then you have to load msr module before.

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sudo modprobe msr

KVM problem
KVM module works a bit differently than VB. E.g. in case of AMD KVM sets SVME immediately after loading. So having KVM module loaded, you'll get following, and a bit misleading, message in VB:

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HWACCM: No VT-x or AMD-V CPU extension found. Reason VERR_SVM_IN_USE

Misleading is only a first part, reason is correct.

Solution
To unload KVM modules type:

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sudo modprobe -r kvm_amd kvm_intel

It will be a bit off-topic now, but still may be useful for somebody.

Checking whether hardware virtualization is permanently (in current session) disabled
For AMD CPU to check whether you can use hardware virtualization, i.e. it wasn't blocked by BIOS, etc. you have to look at SVME_DISABLE bit (4th, counting from 0) in VM_CR (MSR 0xC0010114).

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sudo rdmsr 0xC0010114 #VM_CR

If you get a number where 2nd (counting from 1) hexadecimal digit has first bit set, or it just equals 1, then your hardware virtualization is not available in this session.

przemoc wrote:
Solution
To unload KVM modules type:
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sudo modprobe -r kvm_amd kvm_intel

That's it!
Thanks for the explanation!

Just for the reference (for old hardware users/googlers), some possibly useful information (on topic of AMD-V activated, or not?) can be found in my comments on ticket 1933, in particular:

AMD CPU F2 stepping has buggy virtualization, that requires special support in BIOS.
Hardware virtualization feature may be misnamed in BIOS, i.e. having reversed meaning.

virtualbox.org

AMD-V activated, or not?

AMD-V activated, or not?

Re: AMD-V activated, or not?

Re: AMD-V activated, or not?

Re: AMD-V activated, or not?

Re: AMD-V activated, or not?